The 21st Asian Workshop on
First-Principles
Electronic Structure Calculations(ASIAN-21)

October 29 — 31, 2018
Fusion Hall, KI Building
KAIST
Daejeon, Korea

International Organizing Committee
Chang, Kee Joo (KAIST)
Chou, Mei-Yin (Academia Sinica)
Fang, Zhong (Chinese Academy of Sciences)Gong, Xin-Gao (Fudan University)
Guo, Guang-Yu (National Taiwan University)
Ihm, Jisoon (POSTECH)
Oguchi, Tamio (Osaka University)
Oshiyama, Atsushi (Nagoya University)
Tanaka, Isao (Kyoto University)
Watanabe, Satoshi (University of Tokyo)
Yu, Jaejun (Seoul National University)

Local Organizing Committee
In-Ho Lee (KRISS)

Chair

Yong-Hyun Kim (KAIST)

Co-ChairHyoung Joon Choi (Yonsei University)

Chair, ASIAN-17

Seung-Hoon Jhi (POSTECH)

Chair, ASIAN-13

Yong-Hoon Kim (KAIST)

Chair, ASIAN-9

Hyunju Chang (KRICT)
Byungchan Han (Yonsei University)
Myung Joon Han (KAIST)
Seungwu Han (Seoul National University)
Young-Kyun Kwon (Kyung Hee University)
Sung-Hoon Lee (Kyung Hee University)
Cheol-Hwan Park (Seoul National University)
Chul Hong Park (Busan National University)
Noejung Park (UNIST)
Young Woo Son (KIAS)

Timetable
10/29 (Monday)

10/30 (Tueday)

10/31 (Wednesday)

9:00 – 9:45
( Louie )9:45 – 10:15( Chou )10:15 – 10:45(30-min Break)
10:45 – 11:15( Quek )11:15 – 11:45( Mahadevan )11:45 – 12:15( Sun )
12:15 – 14:00(Lunch)14:00 – 14:45( Marzari )14:45 – 15:30( Blum )15:30 – 16:30(Photo/Poster)
16:30 – 17:00( D. Kim )17:00 – 17:30( Morikawa )17:30 – 18:00( Jungsuttiwong )9:00 – 9:45
( Gonze )9:45 – 10:15( Togo )10:15 – 10:45(30-min Break)
10:45 – 11:15( Matsushita )11:15 – 11:45( Han )
11:45 – 12:15( C. Kim )12:15 – 14:00(Lunch/IOC Meeting)
14:00 – 14:45( Wei )
14:45 – 15:15( Seo )
15:15 – 16:15(Poster)
16:15 – 16:45( Zhang )16:45 – 17:15( Ishii )17:15 – 17:45( Huang )18:00 – 21:00(Banquet)

9:00 – 9:30
( Watanabe )9:30 – 10:00( Suzuki )10:00 – 10:30( Park )10:30 – 10:45(15-min Break)
10:45 – 11:15( Chang )11:15 – 11:45( Wan )
11:45 – 12:15( Lin )
12:30 – 18:00(Lunch/Tour)
Baekje UNESCO
Heritage tour

Homepage
http://events.kias.re.kr/AES21

Program
Oct. 29 (Monday)(Registration @ Fusion Hall, KI Building, KAIST)
8:30 – 18:00(Welcome Session)
8:50 – 9:00 Opening Remark – Prof. Yong-Hoon Cho (Associate Vice President of
Academic Affairs, KAIST, Korea)(Session 1): Physics of Low-Dimensional Materials - Chair: Prof. Kee Joo Chang(KAIST, Korea)
9:00 – 9:45
Prof. Steven G. Louie (UC Berkeley, USA)
Title: Topological and Interaction Effects in Atomically Thin 1D & 2D Materials
9:45 – 10:15
Prof. Mei-Yin Chou (Academia Sinica, Taiwan)
Title: Topics of Two-Dimensional Materials and Their Heterostructures(30-min Coffee Break)
10:15 – 10:45(Session 2): Novel 2D Materials - Chair: Prof. Suhuai Wei (Beijing Computational
Science Research Center, China)
10:45 – 11:15
Prof. Su Ying Quek (National University of Singapore, Singapore)
Title: Electronic and Optical Properties of 2D-material-based Heterostructures
11:15 – 11:45
Prof. Priya Mahadevan (S. N. Bose National Centre for Basic Sciences, India)
Title: Engineering spin-valley physics in bilayers of MoSe2
11:45 – 12:15
Prof. Jiatao Sun (Chinese Academy of Sciences, China)
Title: First-principles investigations of nonequilibrium states of periodically driven black
phosphorous(Lunch)12:15 – 14:00* Plenary/Invited speakers and local/international committee members are invited to thelunch at the Faculty Club.

(Session 3): State-of-the-Art Computation - Chair: Prof. Jisoon Ihm (POSTECH,
Korea)
14:00 – 14:45
Prof. Nicola Marzari (EPFL, Switzerland)
Title: 2D, or not 2D?
14:45 – 15:30
Prof. Volker Blum (Duke Univ., USA)
Title: All-electron electronic structure theory for new materials for light harvesting andlight emission(Session 4): Recent Progress in Electronic Structure Calculations
15:30 – 16:30 Photo session/Poster presentation(Session 5): Energy Materials - Chair: Prof. Isao Tanaka (Kyoto Univ., Japan)
16:30 – 17:00
Dr. Donghun Kim (KIST, Korea)
Title: Novel Materials for Ferroelectric Photovoltaics
17:00 – 17:30
Prof. Yoshitada Morikawa (Osaka University, Japan) – Oct. 29 or 30
Title: First-principles theoretical study of catalytic reactions at surfaces and interfaces
17:30 – 18:00
Prof. Siriporn Jungsuttiwong (Ubon Ratchathani Univ., Thailand)
Title: DFT Mechanistic Study of Carbon-Doped Boron Nitride Nanosheet as Highly
Efficient Metal-Free Catalyst for NO Reduction

Oct. 30 (Tuesday)(Registration @ Fusion Hall, KI Building, KAIST)
8:30 – 18:00(Session 6): Phonon Effect - Chair: Prof. Jaejun Yu (Seoul National Univ., Korea)
9:00 – 9:45
Prof. Xavier Gonze (Uni. Cath. Louvain, Belgium)
Title: Vibrational effects in electronic structure: Temperature dependence, zero-point
motion, spectral functions
9:45 – 10:15
Prof. Atsushi Togo (Kyoto university, Japan)
Title: High-throughput first-principles phonon calculation and phonon database(30-min Coffee Break)
10:15 – 10:45(Session 7): Electron Correlation - Chair: Prof. Tamio Oguchi (Osaka Univ., Japan)
10:45 – 11:15
Prof. Yu-ichiro Matsushita (Tokyo Institute of Technology, Japan)
Title: Quasiparticle spectra based on wave function theory: Application of coupled-cluster
theory and self-energy functional theory
11:15 – 11:45
Prof. Myung Joon Han (KAIST, Korea)
Title: Toward the Better First-principles Description of Correlated Materials: Old
Functionals and New Concepts
11:45 – 12:15
Dr. Choong H. Kim (IBS, SNU, Korea)
Title: Spin-orbital-entangled Jeff=1/2 state in 3d transition metal oxide CuAl2O4(Lunch/IOC Meeting)
12:15 – 14:00* Plenary/invited speakers and local/international committee members are invited to thelunch at the Faculty Club.
** The IOC meeting will take place at the conference room in the Faculty Club.
(Session 8): Defects in Semiconductors - Chair: Prof. Chul Hong Park (Pusan
National Univ., Korea)
14:00 – 14:45
Prof. Suhuai Wei (Beijing Computational Science Research Center, China)
Title: First principle investigation of defect properties in energy materials
14:45 – 15:15
Hosung Seo (Ajou Univ., Korea)
Title: First-principles theory of defect-based qubits in heterogeneous semiconductors

(Session 9): Recent Progress in Electronic Structure Calculations
15:15 – 16:15 Poster presentation (continued)(Session 10): Novel Electronic States - Chair: Prof. Atsushi Oshiyama (Nagoya Univ.,
Japan)
16:15 – 16:45
Prof. Dong-Bo Zhang (Beijing Computational Science Research Center, China)
Title: Strain-Induced Half-Metallic States in Graphene: Application of Generalized
Bloch Theorem
16:45 – 17:15
Prof. Fumiyuki Ishii (Kanazawa University, Japan)
Title: First-principles study of Berry-phase-mediated thermoelectric effects
17:15 – 17:45
Prof. Li Huang (Southern University of Science and Technology, China)
Title: Origin of high thermoelectric performance in n- and p-type SnSe crystals(Banquet @ The Academic Cultural Center)
18:00 – 21:00* All participating principal investigators are invited to the banquet.

Oct. 31 (Wednesday)(Session 11): Machine Learning & TDDFT - Chair: Prof. Young-Woo Son (KIAS, Korea)
9:00 – 9:30
Prof. Satoshi Watanabe (The University of Tokyo, Japan)
Title: Atom dynamics in solids studied by machine-learning techniques
9:30 – 10:00
Prof. Yasumitsu Suzuki (Tokyo University of Science, Japan)
Title: TDDFT study of electron scattering processes
10:00 – 10:30
Noejung Park (UNIST, Korea)
Title: Band topologies and spin-phonon dynamics of spin-orbit coupled insulators: a
study with the real-time TDDFT(15-min Coffee Break)
10:30 – 10:45(Session 12): Topological Materials - Chair: Prof. Guang-Yu Guo (National Taiwan
Univ., Taiwan)
10:45 – 11:15
Prof. Tay-Rong Chang (National Cheng Kung University, Taiwan)
Title: Topological crystalline insulator: from symmetry indicators to material discovery
11:15 – 11:45
Prof. Xian-Gang Wan (Nanjing Univ., China)
Title: Towards ideal topological materials: Comprehensive database searches using
efficient symmetry indicators
11:45 – 12:15
Prof. Hsin Lin (Academia Sinica, Taiwan)
Title: Topological Materials(Closing Session)
12:15 – 12:20 Closing Remark - Prof. Kee Joo Chang (KAIST, Korea)(Tour)
12:30 – 18:00 Baekje UNESCO Heritage Tour
* Gathering place: Bus Stop by The Duck Pond

Posters
PO-1
Soungmin Bae (KAIST)
Density functional study of phonon-induced photocarrier capture in defective MoSe2
PO-2
Xiangyan Bo (Nanjing University)
withdrawn
PO-3
Iulia Emilia Brumboiu (KAIST, KTH)
The Influence of Electron Correlation on the Electronic Structure of Transition Metal
Phthalocyanines
PO-4
Sanggyun Byeon (Sungkyunkwan University)
withdrawn
PO-5
Seongjae Byeon (KAIST)
Computational study of strain effect on the electronic properties of Cu-doped CdSe
nanoplatelets
PO-6
Supparat Charoenphon (Kasetsart University)
Energetics and optical properties of carbon impurities in rutile TiO2
PO-7
Yifeng Chen (National University of Singapore)
Defect induced exciton states in transition metal dichalcogenide WSe2 monolayer fromfirst principles
PO-8
Young-Jae Choi (POSTECH)
Phonon-calculation validity of neural-network-potential
PO-9
Ji-Hae Choi (POSTECH)Emergence of Out-plane Ferroelectricity in Atomically Thin A0.5B0.5X2 (A=W Mo; B=Re
Tc; X=S Se Te) Monolayer
PO-10
Min Choi (Ulsan National Institute of Science and Technology)
Excited electron dynamics in the 2H/1T heterophase of monolayer MoS2 and its phaseengineering: real-time time dependent density functional theory study
PO-11
Young Woo Choi (Department of Physics, Yonsei University)
Structural relaxation electronic structure and electron-phonon coupling in magic-angle
twisted bilayer graphene
PO-12
Feng-Chuan Chuang (National Sun Yat-sen University)
withdrawn
PO-13
You Kyoung Chung (SungKyunKwan University)
The structural and electronic properties of Mo6S3I6 nanowires by theoreticalcompositional arrangement
PO-14

Klichchupong Dabsamut (Kasetsart University)

First-principles Calculations of Stacking Stability of C2N Bilayer Nanosheet
PO-15
Igor Di Marco (APCTP)
Standard model of the Rare-Earths analyzed from the Hubbard I approximation
PO-16
Alexey Dyachenko (Russian Academy of Sciences)
DFT+DMFT study of phase transitions with a large volume collapse in MnSe underpressure
PO-17
Yoshiyuki Egami (Hokkaido University)
First-Principles Study on Electron Transport Properties of Halogenated Graphene
PO-18
Liang Ying Feng (National Sun-yat Sen University)
Predicting topological insulators in hydrogenated transition metal dichalcogenide
monolayers: A first-principles study
PO-19
Masahiro Fukuda (Project researcher of Institute for Solid State Physics,
University of Tokyo)
Structure exploration for AB2 type monolayers by high-throughput DFT calculations
PO-20
Pankajkumar Gajjar (Gujarat University)
withdrawn
PO-21
Hui-Jun Gu (Fudan University)
Intermediate-phase Method for Computing the Natural Band Offset between Two
Materials with Dissimilar Structures
PO-22
Satoshi Hagiwara (National Institutes for Quantum and Radiological
Science and Technology)
Theoretical study on positronium formation at metal surfaces based on two-component
density functonal theory
PO-23
Woo Hyun Han (KAIST)
A hybrid approach combining artificial neural network potentials with first-principles
calculations
PO-24
GyuSeung Han (KIST)
Phase Diagram of Ga (As Sb) and (In Ga)As by Cluster Expansion and DFT Calculations
PO-25
Koki Harada (Tokyo University Of Science)
Water droplet affects charge distribution of carbon nanotube
PO-26
Xin He (Jilin University)
Swarm-Intelligence Guided Computational Design of Novel Silicon Allotropes
PO-27
Keiya Hiraoka (ISIR-SANKEN, Osaka University, Japan)
A first-principle study on the magnetism of Fe/Bi/MgO multilayers
PO-28
Hikaru Horii (Tokyo University of Science)
Tunable Thermoelectric Effects of Bilayer Graphene by Vertical Electric Field

PO-29Bao-Huei Huang (Department of Physics, National Central University)
Noncollinear Spin Torque Effect in Magnetic Heterojunctions: Combined First-Principles
Calculation and TB-NEGF Method
PO-30
Jun Inagaki (TamKang University)
Polarization dependent optical response and layer-controlled band gap of group IV
monochalcogenides
PO-31
Keisuke Ishizeki (Tokyo University of Science)
Electronic transport simulation in nitrogen-doped carbon nanotubes focusing on
disappearance of Anderson localization due to phonon scattering
PO-32
Seung Woo Jang (KAIST)
Microscopic understanding of magnetic interactions in bilayer CrI3
PO-33
Sunam Jeon (Sungkyunkwan University)
Type-I and Type-II nodal lines in a magnetic hexagonal InC sheet
PO-34
Min Yong Jeong (Department of Physics, KAIST)DFT+DMFT study of Pressure dependent Insulator-to-Metal transition in molecular Jeff =3/2 Mott insulator GaTa4Se8
PO-35
Jaemo Jeong (SungKyunKwan University)
Topological Phase Transition in NaZnBixSb1−x
PO-36
Il-Seok Jeong (GIST)
withdrawn
PO-37
Hyo Sun Jin (Korea Univ.)
Weyl and Triple Nodal Points in half-metallic ferrimagnets
PO-38
Minwoong Joe (SKKU)
Dominant in-plane cleavage direction of CrPS4 monolayer
PO-39
Jong Hyun Jung (Seoul National University)
A Simple Method to Calculate the Exfoliation Energies of Layered Materials
PO-40
Sirichok Jungthawan (Suranaree University of Technology)First-Principles Study of Alkali Metal Intercalated MoS2
PO-41
Sungmo Kang (Seoul National University)
Quantum Anomalous Hall Effect with Higher Chern Numbers in Electron-Doped CrSiTe3:
A First-Principles Prediction
PO-42
Narissa Kanlayakan (Chiang Mai University)
Path Integral Molecular Dynamics Simulations for Muoniated Thioformaldehyde
Radicals
PO-43
Mitsuaki Kawamura (The Institute for Solid State Physics)
Benchmark of density functional theory for superconductors in elemental materials

PO-44
Muhammad Ejaz Khan (KAIST)
Semimetallicity and Negative Differential Resistance from Hybrid Halide Perovskite
Nanowires
PO-45
Yeil Kim (Yonsei Univ.)
Non-Covalent Interactions in Density Functional Calculations
PO-46
Hu Sung Kim (KAIST)
Odd-even phonon transport effects in strained carbon atomic chains bridging graphene
nanoribbon electrodes
PO-47
Min-Cheol Kim (KIST)
Abnormalities in Density Functional Calculations on Ions and Radicals and its solution:
Density-Corrected Density Functional Theory
PO-48
Do Hoon Kim (KAIST)First-principles-based calculation of branching ratio for 5d, 4d and 3d transition metal
systems
PO-49
Hyun Woo Kim (KRICT)
Comparing two mapping formalisms for mixed quantum-classical simulations of complex
systems
PO-50
Eunmi Kim (UNIST)
withdrawn
PO-51
Tae Hyung KIM (KAIST)
Atomistic origins of low-resistance metal contacts to phase-engineered MoS2
PO-52
Dongwook Kim (Sungkyunkwan University)
Z 2 monopole nodal lines in ABC graphdiyne
PO-53
Yusei Kioka (Department of Electrical Engineering, Tokyo University of
Science, Tokyo, 125-8585)
Ab Initio Calculations of Electrical Structures of Water Adsorbed on Graphene
PO-54
Eunjung Ko (KIST)
First-Principles Electronic Transport Properties of Ge/amorphous Al2O3/Au Structures
PO-55
Takao Kosaka (ISIR-SANKEN, Osaka University, Japan)
DFT-based engineering of Dirac surface states in topological insulator multilayers
PO-56
Taichi Kosugi (University of Tokyo)
Can exact KS potential reproduce HOMO-LUMO gap? : analytically solvable twoelectron system
PO-57
Lin Kuan Bo (Academia Sinica, RCAS)
Electronic transport through Ni/ZrO2 interface: First-principles calculation
PO-58
Artem Kuklin (Kyungpook National University)
Topological Stability of Two-Dimensional Penta-Structures: a case of PdSe2

PO-59Rameshbabu Kunchala (National Taiwan Univ.)
Electron-Phonon Coupling Superconductivity and nontrivial Band Topology in NbN
Polytypes
PO-60
Fumiaki Kuroda (Osaka University)
Carrier doping effect on all-Heusler giant-magnetoresistance junctions with semimetallic
Fe2VAl studied by first-principles calculations
PO-61
Viet-Duc Le (KAIST)First-principles Study of Band Gap Tunability in Hydrogenated Graphene
PO-62
Seunghyun Lee (KBSI, UNIST)
Chemical degradation of OLED host materials: the role of excited carriers in non-local
interaction
PO-63
Chi-Cheng Lee (The University of Tokyo)
Revisiting Anomalous Hall Conductivity in BCC Iron via First-Principles Tight-Binding
Calculations using Pseudo Atomic Orbitals
PO-64
Yea-Lee Lee (Korea Research Institute of Chemical Technology)
Topological Phases in One-dimensional Graphene Nanoribbons
PO-65
Hyunggeun Lee (KAIST)
Revisit to the molecular Jeff ground state of lacunar spinel compounds: A charge-density
functional plus U study
PO-66
Weon-gyu Lee (SKKU)New One-Dimensional Material Nb2Se9: Theoretical Prediction of Indirect to Direct Band
Gap Transition Due to Dimensional Reduction
PO-67
Seungjun Lee (Kyung Hee University)
Versatile physical properties in new two-dimensional van der Waals materials composedof group IV-V elements
PO-68
Kyeongpung Lee (Seoul National University)
First-principles investigation on Al doping in SrTiO3
PO-69
Jaichan Lee (Sungkyunkwan University)
withdrawn
PO-70
Juho Lee (KAIST)
Silicon Passivation of Zigzag Graphene Edge for Spintronic Nanosensor Applications
PO-71
Tianshu Li (Jilin University)
First-principles Calculations of Intrinsic Defect Properties in Halide Double Perovskites
for Optoelectronic Applications
PO-72
Wei Liu (The University of Tokyo)
Voltage Dependence of Ni-Li Electrode on its Composition and Structure: A Density
Functional Theory Study

PO-73Gennevieve Macam (National Sun Yat-sen University)
Prediction of Quantum Anomalous Hall Effect in MBi and MSb (M:Ti
Honeycombs

Zr

and Hf)PO-74
Aniceto III Maghirang (National SUN YAT-SEN Univ.)
Two-dimensional topological insulators upon substitutional doping of monolayer VB-VIA
transitional metal dichalcogenides
PO-75
Hong-guk Min (Sungkyunkwan University (skku))
Topological Dirac Insulator in a Nonsymmorphic Circuit Lattice
PO-76
Susumu Minami (Kanazawa University)
First-principles study of anomalous Nernst effect in Fe3Al and related compounds
PO-77
Hiroyoshi Momida (Osaka University)
Guiding Principles for Enhancing Piezoelectricity in Wurtzite Materials: First-Principles
Calculations
PO-78

Sutassana Na Phattalung (Walailak University)

Magnetic states and intervalence charge transfer of Ti and Fe defects in α-Al2O3: The
origin of the blue in sapphire
PO-79
Masao Obata (Kanazawa University)
Magnetic Dipole-dipole Energy Evaluation on 1D 2D and 3D Periodicities using Density
Functional Approach
PO-80
Yun-Tak Oh (Department of physics, Sungkyunkwan University)
Three-dimensional Dirac semimetal in a nonsymmorphic wallpaper multi-layer
PO-81
Taisuke Ozaki (Univ. of Tokyo)
Efficient O(N) divide-conquer method with localized natural orbitals
PO-82
Eun-Won Park (Sookmyung Women's University)
Simulated Scanning Tunneling Microscope Images of Intrinsic Defects in MoTe2
PO-83
Hanjin Park (Kyung Hee University)
First Principle Study of Non-thermal Phase Transition Mechanism with Uniaxial Stress
Applied Phase Transition Material : GeTe
PO-84
Jae-Hyeon Parq (Seoul National University)
Estimation of the Effective On-Site Coulomb Interaction Parameter U by Mapping Atomic
Self-Interaction Correction onto GGA+U for Molecules
PO-85
Lien Pham Thi Thanh Tan (University of Ulsan)
Computational predictions of stable phase for antiperovskite Na3OCl via rotation of ONa6octahedra
PO-86
Thantip Roongcharoen (Chiang Mai University)
Theoretical insight into methane oxidation to methanol on single Fe-embeded nitrogendoped graphene

PO-87
Junga Ryou (KAIST)
Edge Effect of Graphene Adsorbed on the ZnO Surface : A First Principles Study
PO-88
Hirofumi Sakakibara (Tottori University)
Model mapped RPA: first-principles method to determine a Hubbard model Hamiltonian
PO-89
Rusrina Salaeh (Chiang Mai University)
Electronic and Photophysical Properties of Derivatives of 2-Phenylbenzothiazole and 2(2´-Hydroxyphenyl) benzothiazole: Effect of Intramolecular Hydrogen Bonding
PO-90
Abdus Samad (University of Ulsan)
Ferroelectricity and Piezoelectricity in stable monolayers MoC WC WS and WSe
PO-91
Hikaru Sawahata (Kanazawa University)
First-principles study of Electric-field induced Z2 topological phase transition in strained
one-bilayer Bi(111)
PO-92
Smritijit sen (Department of Physics and Center for Theoretical Physics,
National Taiwan University)
First Principles Investigations on a New 1111-type Fe-based Superconductor: ThFeAsN
PO-93
Insung Seo (Dept. Mater. Sci. Eng., Tokyo Institute of Technology,
Japan)First-Principles Study of Ir Desorption from Its Low-index Surfaces
PO-94
Aamir Shafique (University of Ulsan)
The effect of strain on the phonon thermal transport properties of the two-dimensional
2H-MoTe2
PO-95
JaeHwan Shim (Seoul National University)
OpenMX interface for the Atomic Simulation Environment
PO-96
Koji Shimizu (The University of Tokyo)
Construction of Neural Network Potential to Study Li-Ion Distribution nearAu(111)/Li3PO4 Interface
PO-97
Mahbubul Alam Shoaib (University of Ulsan)
Oxygen adsorption and oxygen dissociation on TiB2 monolayer.
PO-98
Jae-Hoon Sim (KAIST)Open source code development for DFT + DMFT calculation: correlated subspace
projection and analytic continuation
PO-99
Youngjoon Song (Korea University)
Searching for Antiferromagnetic Topological Phases
PO-100Suhwan Song (Yonsei Univ.)
Correcting DFT problems for the spin-state of transition metal complexesPO-101
Wan-Sheng Su (National Taiwan Science Education Center)
Structural and electronic properties of α-Te tubular nanostructures: a first-principles
study
PO-102Chattarika Sukpattanacharoen (Chiang Mai University)
Heteroatom effect on electronic and photophysical properties of 3-hydroxyquinolin-4(H)one and its analogues enhancing in the excited-state intramolecular proton transfer
processes: A TD-DFT study on substitution effect
PO-103
Terumasa Tadano (National Institute for Materials Science (NIMS))First-Principles Study of Phonon Anharmonicity in CsPbBr3
PO-104
Kengo Takashima (Tokyo University of Science)
Variance of GNR FET Characteristics Caused by Anderson localization phenomena
PO-105Feng Tang (Nanjing University)
withdrawn
PO-106
Viet Dung Tran (University of Ulsan)
Surface effects in the (001) BaTiO3 ferroelectric slab from first-principles calculations andphase field simulation
PO-107
Yoshihiro Ueda (Tokyo University of Science)
Secondary Electron Emission from Multi-layer Graphene by TDDFT Simulations
PO-108Hamid Ullah (University of Ulsan)
Defective SnS monolayer as a candidate for long-range ferromagnetism
PO-109Rovi Angelo Beloya Villaos (National Sun-yat Sen University)
Thickness Dependent Electronic Properties of Pt Dichalcogenides - PtX2 (X = S Se andTe)
PO-110
Di Wang (Nanjing University)
withdrawn
PO-111
Yue Wang (Hanyang University)
Local work functions of clean tungsten surfaces under electric fields based on ab initio
calculations
PO-112
Mei-Ling Xu (Department of Physics National Sun Yat-sen University )Prediction of Large-Gap Topological Insulator in functionalized Ordered Double
Transition Metal MXene
PO-113
Liangliang Xu (Hanyang University)
First principles study on electronic properties of magnetite for spin polarized electron
emission
PO-114
Kunihiro Yananose (Seoul National University)
First principle Study on Surface States of Rocksalt SnSe

PO-115
Hyeonwoo Yeo (KAIST)Electrochemical potential profiles of molecule junctions using constrained-search density
functional study
PO-116
In Won Yeu (Seoul National University)
Vibrational effects on the surface energy of III-V compound semiconductors using abinitio thermodynamics
PO-117
Hongkee Yoon (KAIST)
Analytic continuation via “domain-knowledge free” machine learning
PO-118
Daiki Yoshikawa (Kanazawa University)
First-Principles Density Functional Study in the Magnetically and Electrically polarized
Pt/CoO/ZnO
PO-119Kanako Yoshizawa (Research Organization for Information Scienceand Technology)
Performance information of first-principles codes in K computer
PO-120Nan Zhao (Hanyang University)
First principles study on electronic properties of graphene nanostructures for high current
density cathodeAbstracts
Oral Presentations

[Invited talk: 9:00 – 9:45, Oct.29, 2018]

Topological and Interaction Effects in Atomically Thin 1D &2D Materials
Steven G. Louie1,*
1

Physics Department, University of California at Berkeley, and Lawrence Berkeley
National Lab, Berkeley, California 94720 U.S.A.
*

E-mail: sglouie@berkeley.edu

Symmetry, interaction and topological effects, as well as environmental screening,
dominate many of the quantum properties of reduced-dimensional systems andnanostructures. These effects often lead to manifestation of counter-intuitive concepts
and phenomena that may not be so prominent or have not been seen in bulk materials.
In this talk, I present some fascinating physical phenomena discovered in recent studies
of atomically thin one-dimensional (1D) and two-dimensional (2D) materials. A
number of highly interesting and unexpected behaviors have been found – e.g., strongly
bound excitons (electron-hole pairs) with unusual energy level structures and new
topology-dictated optical selection rules; tunable magnetism and plasmonic properties;
novel topological phases; correlated multi-particle excitations; etc. – adding to theoutstanding promise of 1D and 2D materials for exploration of new science and valuableapplications.
This work was supported by the U. S. Department of Energy, National Science
Foundation, and Office of Naval Research.

[Invited talk: 9:45 – 10:15, Oct.29, 2018]

Topics of Two-Dimensional Materials and Their
Heterostructures
Chih-Piao Chuu,1 Chi-Ruei Pan,2 Kuan-Sen Lin,3 and Mei-Yin Chou1,2,3,*
1

Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
School of Physics, Georgia Institute of Technology, Atlanta, Georgia, U.S.A.
3
Department of Physics, National Taiwan University, Taipei, Taiwan

2*E-mail: mychou6@gate.sinica.edu.tw

It has become possible in recent years to fabricate and manipulate two-dimensional
nanomaterials in the laboratory that are as thin as one to few atomic layers. The reduced
dimensionality gives rise to unique physical and chemical properties that differ from thoseof traditional bulk materials, and intriguing physical properties have been found in these
few-layer systems. Computational studies have played a central role in understanding andpredicting these novel properties. In this talk, I will focus on a few representative systems,
including graphene systems and monolayers of transition metal dichalcogenides thatexhibit properties ranging from charge density waves [1] to the quantum spin-Hall effect[2]. The hybrid system of boron nitride and graphene (h-BNC) at low BN doping serves
as an ideal platform for band-gap engineering and valleytronic applications. The
calculations find a linear dependence of the band gap on the BN concentration at low
doping, arising from an induced effective on-site energy difference at the two C
sublattices as they are substituted by B and N dopants alternately. In addition, ourcalculations show that the Moiré patterns in van der Waals heterostructures will modify
the local band gap, interlayer interaction, and structural parameters [3-5]. I will also
discuss one-dimensional topological insulators manifested in graphene nanoribbons, inwhich localized spin states may exist at the end or near the junctions. A symmetry
protected 𝑍 topological classification is formulated for any type of termination with𝑎 𝜋-quantized Berry phase when summed over all occupied bands.

[1] P. Chen et al. Nature Communications 8, 516 (2017).
[2] P. Chen et al. Nature Communications 9, 2003 (2018).
[3] Q. Zhang et al. Nature Communications 7, 13843 (2016).
[4] C. Zhang et al. Science Advances 3, e16001459 (2017).
[5] Q. Zhang et al. ACS Nano 12, 9355 (2018).

[Invited talk: 10:45 – 11:15, Oct.29, 2018]

Electronic and Optical Properties of 2D-material-based
Heterostructures
Su Ying Quek1,*
1

Department of Physics and Centre for Advanced 2D Materials, National University ofSingapore, Singapore*

E-mail: phyqsy@nus.edu.sg

The atomically thin nature of layered two-dimensional (2D) materials results in emerging
properties that are different from their bulk counterparts. One often cited example is the
reduced electronic screening resulting in stronger exciton binding energies in 2D
materials. 2D materials are also interesting because of the potential for bottom-up designof various flexible heterostructures. In this regard, it is important to understand how thedifferent components of the heterostructure affect the electronic and optical properties ofthe system. We will discuss 2D-material heterostructures based on the elemental material
phosphorene, as well as hybrid organic-2D-material heterostructures. Using state-of-theart GW+BSE methods, we show that bright interlayer excitons exist in the direct band
gap phosphorene (BP)-based heterostructures (BP/GeS and BP/hBN), with a goodcompromise between binding energies, oscillator strength and radiative lifetimes.[1]Strong hybridization between GeS and BP increases the effective mass and room
temperature exciton lifetimes, while the hBN spacer layer decouples the BP monolayers
in BP/hBN/BP, resulting in the lowest energy exciton becoming dark. A single hBN layer
reduces the exciton binding energy in monolayer BP by ~0.11 eV, while adding anotherhBN layer in hBN/BP/hBN further reduces the binding energy by ~0.03 eV. This brings
us to our next topic, which is to investigate how a 2D material screens excitations adjacent
to it, such as excitations in adsorbed molecules. We show that the extent to which amaterial screens the band gap of small adsorbed benzene molecules is given by thescreening potential Vscr(r,r) at the position of the molecule. Interestingly, by computing
Vscr(r,r) for a range of 2D materials and slabs of 3D materials, we find that Vscr(r,r) at agiven distance away from the material scales approximately linearly with thequasiparticle gap in the same manner for all these materials. This is in contrast to thescreening of excitations within materials, which differ significantly between 2D and 3D
materials. Finally, if time permits, we will discuss Raman optical spectra for organics on
2D materials, where electron-phonon coupling leads to interesting chemical enhancement
effects.
[1] Y. Chen, and S. Y. Quek, 2D Materials 5, 045031 (2018).

[Invited talk: 11:15 – 11:45, Oct.29, 2018]

Engineering spin-valley physics in bilayers of MoSe2
Priya Mahadevan
Department of Condensed Matter Physics and Material Science
S.N.Bose National Centre for Basic Sciences, Kolkata, India
Monolayers of transition metal dichalcogenides (MX2, M=Mo,W) are found to havetheir valence band maximum at K point. In most instances when the second layer is added,
the interaction between the two layers results in the valence band maximum shifting toGamma. As the valence band maximum at K point is contributed primarily by dxy anddx2-y2 orbitals of the transition metal atom, one finds that spin-orbit interactions lead tolarge spin splittings of the valence band maximum. This has interesting consequences as
spin-orbit interactions alone cannot lead to magnetic order. This then implies that the spin
splitting at the symmetry point -K is opposite in direction to that at K. In this talk I will
present our recent results of how the spin splittings evolve for bilayers of MoSe2 .
This is work done in collaboration with Poonam Kumari and Joydeep Chatterjee.

[Invited talk: 11:45 – 12:15, Oct.29, 2018]

First-principles investigations of nonequilibrium states of
periodically driven black phosphorous
Jiatao Sun1,*1

Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China*

E-mail: jtsun@iphy.ac.cn

Recent advances in ultrafast spectroscopy open a route toward engineering new phase ofsolids with optical pumping. The nonequilibrium electronic states of solids driven by theelectromagnetic field manifest novel topological states which don't exist at equilibrium
conditions. Using first-principles calculations and Floquet theorem, we studied the
dressed states of black phosphorous and graphene under periodic driving by laser.
Intriguing photo-dressed electronic states including Floquet Dirac semimetals, Floquet
topological insulators etc can be engineered in black phosphorous by changing thedirection, intensity and frequency of incident laser [1]. The coexistence of type-I andtype-II Floquet Dirac fermion (FDF) in graphene can be realized simultaneously, which
can be monitored by simulating the pump-probe time and angular-resolved photoelectron
spectroscopy. In the transition boundary between type-I and -II FDF, we found one
critical type-III FDF, which could be utilized to achieve the highest Hawking temperature
TH hitherto reported [2]. Our works demonstrate examples of the nonequilibrium
topological states of two-dimensional materials by first-principles calculations, and open
an avenue towards the Floquet engineering of quantum materials.

[1] H. Liu et al. Phys. Rev. Lett. 120, 237403 (2018).
[2] H. Liu et al. arXiv: 1809.00479

[Invited talk: 14:00 – 14:45, Oct.29, 2018]

2D, or not 2D?
Nicola Marzari1,*
1

Theory and Simulation of Materials (THEOS), and National Centre for
Computational Design and Discovery of Novel Materials (MARVEL), École
Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland*

E-mail: nicola.marzari@epfl.ch

Quantum-mechanical simulations have become massively used tools for scientificdiscovery and technological advancement: thanks to their predictive power they cansuggest, accelerate, support or even substitute actual physical experiments. This is a farreaching paradigm shift, replacing the cost- and time-scales of brick-and-mortar facilities,
equipment, and personnel with those, very different, of computing engines - aiming at
understanding, predicting, or designing the properties and performance of novel orcomplex materials and devices.
I will briefly highlight the current accomplishments and challenges, outline the current
roadmap for materials discovery driven by the convergence of high-performance andhigh-throughput computing, and I will illustrate its potential with the example of novel
two-dimensional and layered materials, displaying promising electronic, optical, or
topological properties [1]. In the process, I will discuss the software stack that we needto deploy to upscale materials simulations towards materials discovery, and therequirements for data curation, dissemination, and reproducibility [2].
[1] Nicolas Mounet, Marco Gibertini, Philippe Schwaller, Davide Campi, Andrius
Merkys, Antimo Marrazzo, Thibault Sohier, Ivano Eligio Castelli, Andrea Cepellotti,
Giovanni Pizzi, Nicola Marzari, Nature Nanotechnology 13, 246–252 (2018).
[2] http://aiida.net; http://materialscloud.org

[Invited talk: 14:45 – 15:30, Oct.29, 2018]

All-electron electronic structure theory for new materials
for light harvesting and light emission
Volker Blum1,*
1

Department of Mechanical Engineering and Materials Science and Department ofChemistry, Duke University, Durham, NC 27708, USA*

E-mail: volker.blum@duke.edu
Materials for light harvesting and light emission are immensely fertile ground forelectronic structure theory, for the simple reason that key physical phenomena behind aparticular materials' function arise at the atomic scale. Key challenges for theory include:
Structures can be complex; the computationally desired phase may compete for stability
with an a priori unknown zoo of possible secondary phases; accurate predictions of
excited-state phenomena in large structures remain a challenge for the field. In this talk,we describe our progress on these issues using the all-electron approach in the FHI-aims
code [1], a high-accuracy, scalable and affordable general-purpose code for molecularand materials simulations. Examples include the nature of polymeric carbon-nitride
materials for photocatalytic hydrogen evolution [2], new quaternary semiconductormaterials I2-II-IV-VI4 (I=Cu, Ag; II=Sr,Ba; IV=Ge,Sn; VI=S,Se) for photovoltaics [3,4],
and identifying the nature of carried levels in layered organic-inorganic perovskites with
optically active organic components by large-scale hybrid density-functional theory[5].
We finally describe ongoing work on an open-source infrastructure "ELSI" to bridge
between electronic structure user codes and massively parallel solver libraries for thelarge-scale (generalized) Kohn-Sham electronic structure problem, and we describe
progress on distributed-parallel GPU architectures.
This overview talk covers joint work with many colleagues around the world, including
the groups of Bettina Lotsch (Stuttgart/Munich), David Mitzi (Duke), Yosuke Kanai(UNC), Matthias Scheffler (FHI Berlin), Xinguo Ren (USTC Hefei), group members at
Duke University, and the very large developer community of the FHI-aims code - allthese and further interactions, as well as support from the National Science Foundationand the US Department of Energy, are gratefully acknowledged.
[1] V. Blum, R. Gehrke, F. Hanke, P. Havu, V. Havu, X. Ren, K. Reuter, and M. Scheffler,Comp. Phys. Commun. 180, 2175 (2009).
[2] T. Botari, W. P. Huhn, V. W.-h. Lau, B. V. Lotsch, and V. Blum
Chem. Mater. 29, 4445 (2017).
[3] T. Zhu, W. P. Huhn, G. C. Wessler, D. Shin, B. Saparov, D. B. Mitzi, and V. Blum,
Chem. Mater. 29, 7868 (2017).
[4] G. C. Wessler, T. Zhu, J.-P. Sun, A. Harrell, W. P. Huhn, V. Blum, and D. B. Mitzi,
Chem. Mater. 30, 6566 (2018).
[5] C. Liu, W. P. Huhn, K.-Z. Du, A. Vazquez-Mayagoitia, D. Dirkes, W. You, Y. Kanai,
D. B. Mitzi, and V. Blum, Phys. Rev. Lett., accepted (2018).
Preprint: arXiv:1803.07230 [cond-mat.mtrl-sci]

[Invited talk: 16:30 – 17:00, Oct.29, 2018]

Novel Materials for Ferroelectric Photovoltaics
Donghun Kim1
1

Korea Institute of Science and Technology

Despite their potential to exceed the theoretical Shockley-Queisser limit, ferroelectric
photovoltaics (FPVs) have performed inefficiently due to their extremely low
photocurrents. In this talk, I will suggest novel ferroelectric materials that are likely to
overcome the challenge, as a result of density functional theory calculations. These works
indicate that the large band-gap and inefficient e-h separations of active layer materials
are the most important issues to be addressed for FPVs to compete with conventional
devices.

[Invited talk: 17:00 – 17:30, Oct.29, 2018]

First-principles theoretical study of catalytic reactions at
surfaces and interfaces
Fahdzi Muttaqien1, Thanh Ngoc Pham1,2, Septia Eka Marsha Putra1,
Son Ngoc Do2, Yuji Hamamoto1, Ikutaro Hamada1, Kouji Inagaki1, andYoshitada Morikawa1,*
1

Department of Precision Science and Technology, Graduate School of Engineering,Osaka University, 2-1 Yamada-oka, Suita 565-0871, Osaka Japan
2
Faculty of Applied Science, Ho Chi Minh City University of Technology, VNUHCM, 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam*

E-mail: morikawa@prec.eng.osaka-u.ac.jp

Chemical reactions at surfaces and interfaces play important roles in wide varieties ofapplications such as hegerogeneous catalysis, electrochemistry, fuel cells, batteries,
etching processes of semiconductor materials, and so on. In this talk, we will present
theoretical investigation and prediction of hydrogenation of CO2 over Cu catalyst[1].
Adsorption and reaction of CO2 on solid surfaces are attracting growing interest becauseof their importance in industrial, energy and environmental management. To clarify
reaction mechanisms and to identify important factors governing the reactivity of CO2 onsolid surfaces are very important to develop more efficient catalysts or catalytic processes
for utilization of CO2. To this end, we investigated CO2 adsorption and hydrogenation[1]on Cu surfaces using van der Waals density functionals as implemented in our home madeSTATE (Simulation tool for Atom TEchnology) program code [2].
We theoretically
proposed a new reaction scheme to enhance the hydrogenation of CO2 on Cu.
In the second topic, we will discuss enhancement of NO dissociation by hydrogenbonding. Nitric oxide (NO) emission from the exhaustive gas of combustion process
has caused negative impacts on the environment, e.g, acid rain, photochemical smog, andozone depletion. So far, catalytic activities for NO dissociation on the Cu surfaces havebeen recognized to be lower than that on Rh. Shiotari et al. experimentally found that thehydrogen bond between NO and water monomers promotes the NO dissociation to takeplace almost barrierlessly on the Cu(110) surface at a very low temperature (~12 K),
which is a promising way to reduce the use of the precious Rh catalyst. would like topoint out importance of the van der Waals density functional for describing . We present
a DFT study to clarify the role of water molecules and the mechanism of the hydrogenbonding induced NO dissociation on the Cu(110) surface[3].
References[1] F. Muttaqien, H. Oshima, Y. Hamamoto, K. Inagaki, I. Hamada, and Y. Morikawa,Chem. Comm., 53, 9222 (2017).
[2] Y. Hamamoto, I. Hamada, K. Inagaki, and Y. Morikawa, Phys. Rev. B, 93, 245440(2016).
[3] Thanh N.Pham, M.Sugiyama, F.Muttaqien, S.E.M.Putra, K.Inagaki, Son Ngoc Do, Y.
Hamamoto, I. Hamada, and Y.Morikawa, J.Phys.Chem. C, 122, 11814 (2018).

[Invited talk: 17:30 – 18:00, Oct.29, 2018]

DFT Mechanistic Study of Carbon-Doped Boron Nitride
Nanosheet as Highly Efficient Metal-Free Catalyst for NO
Reduction
Tanabat Mudchimo1 and Siriporn Jungsuttiwong*
Department of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani
University, Ubon Ratchathani, Thailand

Many of their unique properties and applications of boron nitride nanosheets (hBNs) have been much less recognized. This is the first time for the use of h-BNs as highly
efficient metal-free catalyst for NO catalytic reduction to less-harmful products bydensity functional theory calculations. We found that the CNBNs catalyst showed acomparable energy barrier compared to carbon-based and silicon-based catalysts.
However, the higher thermal stability, intrinsically insulators and excellent
impermeability of CNBNs nanosheets make them superior to other metal-free catalysts inreusability aspect. The results showed that the trans-(NO)2 dimer of CNBNs (D5) is apotentially crucial intermediate with thermodynamically and kinetically favorable, inwhich the calculated barrier for the rate-determining step along the most energeticallyfavorable pathway is 0.62 eV. Hence, we suggest that CNBNs can be used as highly active
metal-free materials in NO removal, which will reduce NO into green products withkinetically, and thermodynamically favorable under ambient conditions.

Keywords: Metal-free catalyst, boron nitride nanosheets, nitrogen oxide reduction, DFT

[Invited talk: 9:45 – 10:15, Oct.30, 2018]

Vibrational effects in electronic structure:
Temperature-dependence, zero-point motion, spectral
functionsXavier Gonze
IMCN, Université catholique de Louvain, B-1348 Louvain-la-neuve, BELGIUM*

E-mail: xavier.gonze@uclouvain.be

Modifications of electronic eigenenergies due to vibrational effects and electron-phonon
coupling are sizable in many materials with light atoms. While often neglected, they havebeen recently computed from first principles using different formalisms, including the
perturbation-based Allen-Heine-Cardona (AHC) theory, in the adiabatic or non-adiabatic
harmonic approximation.
I will provide an overview of the concepts and formalism, and discuss [1]: the DFT and
GW corrections to the diamond bandgap, the latter (0.6 eV) being significantly higher
than the former (0.4 eV); the breakdown of the adiabatic AHC theory for infrared-active
materials, and fix of this problem in the non-adiabatic AHC theory. Then, focusing on thelatter class of materials, I will establish the connection with a simple approach based ona generalized Frohlich Hamiltonian and discuss the near-cancellation between the firstprinciples Fan and Debye-Waller contributions [2].
Other consequences of interactions, visible in ARPES experiments, are broadening of
quasi-particle peaks and appearance of sidebands in the electron spectral function. Migdal
selfenergies and spectral functions will be presented for MgO and LiF. The spectral
function obtained from the Dyson equation makes errors in the weight and energy of thequasi-particle (QP) peak and phonon-induced sidebands. Only one phonon satellite
appears, with an unphysically large energy difference with respect to the QP peak. By
contrast, the spectral function from a cumulant treatment is physically better, giving aquite accurate QP energy and several satellites approximately spaced by the LO phonon
energy. I will provide a detailed comparison between the first-principles results and thoseof the Fröhlich Hamiltonian. Such an analysis applies widely to infra-red active materials.
[1] S. Poncé, G. Antonius, P. Boulanger, E. Cannuccia, A. Marini, M. Côté and X. Gonze,
Computational Materials Science 83, 341 (2014); G. Antonius, S. Poncé, P. Boulanger,
M. Côté and X. Gonze, Phys. Rev. Lett. 112, 215501 (2014); S. Poncé, Y. Gillet, J.
Laflamme Janssen, A. Marini, M. Verstraete and X. Gonze, J. Chem. Phys. 143, 102813(2015); G. Antonius, S. Poncé, E. Lantagne-Hurtubise, G. Auclair, X. Gonze and M. Côté,
Phys. Rev. B 92, 085137 (2015).
[2] A. Miglio, M. Giantomassi, Y. Gillet, G. Antonius, V. Brousseau, M. Côté, and X.
Gonze, in preparation (2018).
[3] J.-P. Néry, P.B. Allen, G. Antonius, L. Reining, A. Miglio, and X. Gonze, Phys. Rev.
B 97, 115145 (2018).

[Invited talk: 9:45 – 10:15, Oct.30, 2018]

High-throughput first-principles phonon calculation andphonon database
Atsushi Togo,1,* and Isao Tanaka2
1

Elements Strategy Initiative for Structural Materials, Kyoto university, Japan
Department of Materials Science and Engineering, Kyoto University, Japan*
E-mail: togo.atsushi.f40@kyoto-u.jp

2

First-principles phonon calculation has been popular in recent scientifc researches. In theharmonic appoximation, now we have enough computational hardware resource toachieve high-throughput phonon calculations for ~10,000 compounds [1-3]. However thehigh-throughput calculations are not a trivial task since we need a sophisticated workflow
engine to systematically execute first-principles phonon calculations. Among workflow
engines, AiiDA [4] and atomate [5] may be the most popular packages. A number ofpeople are working to develop the workflow engines and a lot of efforts have been put
into the development. These developlements are well organized on their github
repositories that are open to everybody indeed. These workflow engines rely on manyother software packages that are also expected to be robust. We have been contributing
to them by providing crystal symmetry finder (spglib [6]) that is widely used inmaterials science. For the first-principles calculations to be run by the workflow engines,
fortunately we have several realistic choices of DFT or DFPT plane-wave
pseudopotential codes such as QUANTUM ESPRESSO, ABINIT, and VASP codes.
To achieve our phonon calculations [3], force constants were calculated in supercells withfinite small atomic displacements (~0.03Å), where the initial crystal structures wereobtained from the materials project [7]. This set of phonon calculations is performed
under the approxmation valid at low temperatures. Thereofre non-negligile number ofcompounds exhibit imaginary modes that may be removed at elevated temperatures. To
treat high temperature properties, several methods have been developted to obtainanharmonic force constants by large atomic displacements [8,9]. Our next challenge ishigh-throughput phonon calculation with anharmonicity for which we still have todevelop robust software environment. We review current computing system to performthe high-throughtput harmonic phonon calculation and discuss what kinds of software
packages will have to be developed for high-throughtput anharmonic phonon calculations.
[1] N. Mounet, et al. Nat. Nanotech., 13, 246, (2018).
[2] G. Petretto, et al. Sci. Data, 5, 180065 (2018).
[3] http://phonondb.mtl.kyoto-u.ac.jp/[4] G. Pizzi, et al. Comp. Mat. Sci. 111, 218-230 (2016); http://www.aiida.net/[5] K. Mathew, et al. Comput. Mater. Sci. 139, 140, (2017); https://atomate.org/[6] arXiv:1808.01590, https://atztogo.github.io/spglib/[7] A. Jain, et al. APL Mater., 1, 011002 (2013), https://materialsproject.org/[8] T. Tadano and S. Tsuneyuki, Phys. Rev. B 92, 054301 (2015).
[9] O. Hellman, et al. Phys. Rev. B 87, 104111 (2013).

[Invited talk: 10:45 – 11:15, Oct.30, 2018]

Quasiparticule spectra based on wave function theory:
Application of coupled-cluster theory and self-energyfunctional theory
Yu-ichiro Matsushita1* and Taichi Kosugi2
1

Laboratory for Materials and Structures, Tokyo Institute of Technology, R3-7, 4259
Nagatsuta Midori-ku Yokohama, Japan2
Department of physics, The University of Tokyo, 7-3-1 Hongo Bunkyo-ku Tokyo,Japan*E-mail: ymatsu@msl.titech.ac.jp

Coupled-cluster singles and doubles (CCSD) is one of wave-function theories
and known as a highly accurate calculation scheme in the field of quantum chemistry.
Recently, the relation between CCSD and GW approximation, which is known as a wellsophisticated calculation method in condensed matter physics, was clarified [1] andCCSD has get growing attention also in condensed matter physics. However, the standard
CCSD scheme cannot yield quasi-particle energy spectra directly. Recently, it has beenreported that by employing the one-particle Green’s function within the CCSD scheme(GFCCSD), one is capable of obtaining physical quantities including energy spectra [2].
Although the GFCCSD method has already been applied to uniform electron gases [3],there is no report of the application to realistic systems.
In this work, we have developed a code to
calculate the quasi-particle energy spectra of isolated atoms andperiodic systems through the GFCCSD method and applied it
to several realistic materials for the first time [4-6]. We havealso applied the self-energy functional theory to the systems forthe first time and clarified the accuracy of the GFCCSD
method. Consequently, we have found that the GFCCSD
method is a powerful tool which enables us to calculate totalenergy and quasi-particle spectra self-consistently. In
particular, the GFCCSD method successfully reproduces quasiparticle bands and satellite peaks at the same time as shown in
Fig.1. Furthermore, we have also shown that the GFCCSD
method can reproduce Mott gaps in finite systems.
[1] M.F. Lange and T.C. Berkelbach, J. Chem. Theory Comput., 14,4224 (2018).
[2] M. Nooijen and J. G. Snijders, Int. J. Quantum Chem. Symp. 44,
55 (1992). M. Nooijen and J. Snijders, Int. J. Quantum Chem. 48, 15 (1993). B. Peng and K.
Kowalski, J. Chem. Theory Comput. 14, 4335 (2018).
[3] J.McClain, J. Lischner, T. Watson, D.A. Matthews, E. Ronca, S.G. Louie, T.C. Berkelbach, and
G.K.L. Chan, Phys. Rev. B 93, 235139 (2016).
[4] Y. Furukawa, T. Kosugi, H. Nishi, and Y.-i. Matsushita, J. Chem. Phys. 148, 204109 (2018).
[5] H. Nishi, T. Kosugi, Y. Furukawa, and Y.-i. Matsushita, J. Chem. Phys. 149, 034106 (2018).
[6] T. Kosugi, H. Nishi, Y. Furukawa, and Y.-i. Matsushita, J. Chem. Phys. 148, 224103 (2018).

[Invited talk: 11:15 – 11:45, Oct.30, 2018]

Toward the Better First-principles Description of CorrelatedMaterials: Old Functionals and New Concepts
Myung Joon Han1, *1

Department of Physics, Korea Advanced Institute of Science and Technology(KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, Korea*

E-mail: mj.han@kaist.ac.kr

In this talk, I will try to give a brief overview of recent progress in my research group fordeveloping first-principle-based computation methods. In the first part, I will discuss
LDA/GGA+U functionals. Although this method has become a standard tool ever since
its first suggestion in 1991, the detailed understanding of the differences in between
various functional recipes has not been reached yet which severely hampers theapplication to real material research. With this motivation, we recently performed thesystematic and comparative analysis on this issue [1,2]. In the second part, I will discussa new physical quantity temporally named as ‘effective degeneracy’ or ‘effective entropy’.
In understanding condensed matter systems, it is sometimes crucially important todevelop or define a new physical concept which carries the key physical intuition. In
order to understand multi-band Mott transitions, we suggest this quantity based on
entropy-like term [3]. Its usefulness will be demonstrated with some materials examples.
Finally (if time allows), I will also introduce our recent developments for the magnetic
force linear response calculation techniques [4] as well as the new analytic continuation
methods [5, 6].

[1] S. Ryee and M. J. Han, Sci. Rep. 8, 9559 (2018).
[2] S. Ryee and M. J. Han, J. Phys.: Condens. Matter. 30, 275802 (2018).
[3] J. -H. Sim et al. Phys. Rev. B (in press).
[4] H. Yoon et al. Phys. Rev. B 97, 125132 (2018).
[5] J. –H. Sim and M. J. Han, arXiv:1804.01683 (submitted).
[6] H. Yoon et al. arXiv:1806.03841 (submitted).

[Invited talk: 11:45 – 12:15, Oct.30, 2018]

Spin-orbital-entangled Jeff =1/2 state in 3d transition metaloxide CuAl2O4
Choong H. Kim,1, 2 H. Cho,1, 2 S. Baidya,1, 2 V. V. Gapontsev,3 S. V. Streltsov,3, 4Daniel I. Khomskii,5 Je-Geun Park,1, 2, Ara Go,6, and Hosub Jin7
1

Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul
08826, Republic of Korea
2
Department of Physics and Astronomy, Seoul National University, Seoul 08826,
Republic of Korea
3
M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of
Sciences, 620137 Ekaterinburg, Russia
4
Ural Federal University, 620002 Ekaterinburg, Russia
5II. Physikalisches Institut, Universit¨at zu K¨oln, D-50937 K¨oln, Germany
6
Center for Theoretical Physics of Complex Systems,
Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea
7
Department of Physics, Ulsan National Institute of Scienceand Technology (UNIST), Ulsan 44919, Republic of Korea
The interplay of spin-orbit coupling (SOC) and Coulomb correlations have become oneof the most active area in condensed matter physics. In particular, the spin-orbitalentangled Kramers pair known as the Jeff=1/2 state has been firstly shown in iridates fromthe intriguing role of large SOC assisted by small electron correlation. The newly found
Jeff=1/2 state has brought about a variety of novel phenomena including the relativistic
Mott phase, Kitaev quantum spin liquid, non-trivial topology, and so on. To date, however,most of studies have been limited to 4d and 5d transition metal compounds, where thecorrelation strength is relatively weak. It is mainly due to the existing consensus that large
SOC strength is a prerequisite for this fully relativistic entity. During the long history of
the 3d transition metal study, SOC has never been a dominating energy scale, rendering
the spin-orbital-entangled state almost impractical. Thus, we are still far fromunderstanding the behavior of the spin-orbital-entangled state under the strong correlation
limit. Here we report on the CuAl2O4 spinel as the first example of a Jeff=1/2 Mott insulator in 3dtransition metal compounds. Density functional theory combined with dynamical mean field
theory calculations reveal that the Jeff=1/2 state survives the competition with the orbitalmomentum-quenched S=1/2 state with the help of strong electron correlation. The fully
relativistic entity found in CuAl2O4 provides insight into the untapped regime where the spinorbital-entangled Kramers pair resides with strong electron correlation.

[Invited talk: 14:00 – 14:45, Oct.30, 2018]

First principle investigation of defect properties in energy
materials
Su-Huai Wei
Beijing Computational Science Research Center, Beijing, China

First-principles study of semiconductor energy materials plays an important role indeveloping clean energy technologies because it can provide useful physical insights,
fresh perspective and new design principles for developing innovative clean energy
materials with high solar power conversion efficiency and reduced cost. Similar to othersemiconductors, one of the most important issues in energy material is to control thedefects, either for introducing charge carrier, improving charge transport, or reducing
non-radiative carrier recombination. For example, a good solar cell material should havegood defect properties so that it can be doped well such that charge carriers can be createdeasily to generate the required electric field and has less defect-induced recombination
centers such that it has high carrier life time and minority carrier mobility, so photogenerated charge can be easily collected. In this talk, using thin-film solar cell absorbermaterials CdTe, CIGS and CZTS as examples, I will discuss how theoretical firstprinciples studies can be used to better understand and improve the solar cell performance.
Control of doping in other optoelectronic energy materials such as TCOs will also be
discussed.

[Invited talk: 14:45 – 15:15, Oct.30, 2018]

First-principles theory of defect-based qubits inheterogeneous semiconductors
Hosung Seo1
1

Department of Physics and Department of Energy Systems Research, Ajou
University, Suwon, Korea*

E-mail: hseo2017@ajou.ac.kr

Recently, significant progress has been made toward full control of the quantum states ofspins and charges in a variety of semiconductors and solid-state nanostructures forapplications in quantum information processing, quantum optics, and quantum sensing.
Such platforms include the NV center in diamond, dopants in silicon, single-photon
emitters in 2-dimensional crystals, and solid-state quantum dots. Being in the solid-state,
the listed platforms also have a significant potential for scalability. In the first part of thetalk, we will outline the principles underlying the listed quantum defect systems in termsof its manipulation and operation schemes. In the second part of the talk, we will highlightsome of our own research efforts [1-6] devoted to the point-defect-based qubits inheterogeneous semiconductors. First, we will discuss the Janus aspects of nuclear spinbaths: the bad being the source of decoherence for electron spin qubits and the good being
useful resources for quantum memory applications. We will show that it is possible toreconcile these conflicting aspects of nuclear spin baths by developing spin qubits either
in heterogeneous crystals or low-dimensional crystals. Second, we will discuss
computational defect designs to search for promising defect candidates in a variety ofheterogeneous semiconductors toward scalable and coherent hybrid quantum systems.
[1] G. Noh, D. Choi, J. Kim, D. Im, Y. Kim, H. Seo, and J. Lee, Nano Lett. 18, 4710
(2018).
[2] M. Ye, H. Seo, and G. Galli, submitted (2018).
[3] H. Seo, H. Ma, M. Govoni, and G. Galli, Phys. Rev. Mater. 1, 075002 (2017).
[4] H. Seo, A. L. Falk, P. V. Klimov, K. C. Miao, G. Galli, and D. D. Awschalom, Nat.
Comm. 7, 12935 (2016).
[5] H. Seo, M. Govoni, and G. Galli, Sci. Rep. 6, 20803 (2016).
[6] W. F. Koehl, H. Seo, G. Galli and D. D. Awschalom, MRS Bull. 40, 1146 (2015).

[Invited talk: 16:15 – 16:45, Oct.30, 2018]

Strain-Induced Half-Metallic States in Graphene:
Application of Generalized Bloch Theorem
Dong-Bo Zhang
Beijing Normal University and Beijing Computational Science Research Center
Su-Huai Wei
Beijing Computational Science Research Center*

E-mail: hseo2017@ajou.ac.kr

Realization of half-metallicity in low dimensional materials is a fundamental challenge
for nano spintronics, which is a critical component for next-generation information
technology. Using the method of generalized Bloch theorem, we show that an in-planebending can induce inhomogeneous strains, which in turn lead to spin-splitting in zigzag
graphene nanoribbons and results in the highly desired half-metallic state. Unlike thepreviously proposed scheme that requires unrealistic strong external electric fields, theobtained halfmetallicity with sizeable half-metallic gap and high energetic stability ofmagnetic order of edge states requires only relatively low-level strain in the in-planebending. Given the superior structural flexibility of graphene and the recent experimental
advances in controllable synthesis of graphene nanoribbons, our design provides ahitherto more practical approach to the realization of half-metallicity in low dimensional
systems.

[Invited talk: 16:45 – 17:15, Oct.30, 2018]

First-principles study of Berry-phase-mediated thermoelectriceffects
Fumiyuki Ishii1*, Yo Pierre Mizuta2 , Susumu Minami2,
Hikaru Sawahata2, and Mineo Saito3
1

Nanomaterials Research Institute, Kanazawa University,
Kakuma, Kanazawa, 920-1192, Japan
2
Graduate School of Natural Science and Technology,Kanazawa Univ.,
Kakuma, Kanazawa, 920-1192, Japan
3
Faculty of Mathematics nad Physics, Institute of Science and Engineering,
Kanazawa University, Kakuma, Kanazawa, 920-1192, Japan*

E-mail: fishii@mail.kanazawa-u.ac.jp

We are interested in how to achieve much higher thermoelectric conversion
efficiency by effectively manipulating electron-spin degree of freedom. As one
possibility, we have been studying Berry-phase-mediated thermoelectric effects, namely
the contribution of the anomalous Hall conductivity (AHC) to thermoelectric power.
What we target here is the anomalous Nernst effect (ANE), which is a heat-to-electricity
conversion observed in magnetic materials and directly related to AHC. We discussed
AHC mainly driven by an effective magnetic field, Berry curvature, induced by spinorbit coupling and/or spin chirality.
In this presentation, we will present our recent first-principles computations [1] on
topological magnet (skyrmion crystals) [2,3] and half-Heusler compounds [4]. We foundthat the effective magnetic field indeed generates large ANE. This behavior was clearly
understood by the chemical potential dependence of AHC. Based on the gained
knowledge, we will discuss how to enhance such Berry-phase-mediated thermoelectriceffects.
[1] T. Ozaki et al. OpenMX, http://www.openmx-square.org.
[2] Y.P. Mizuta and F. Ishii, Scientific Reports 6, 28076 (2016).
[3] Y.P. Mizuta, H. Sawahata, and F. Ishii, Phys. Rev. B (in press). arXiv:1803.08148.
[4] S. Minami, F. Ishii, Y.P. Mizuta, and M. Saito, Appl. Phys. Lett. 113, 032403 (2018).

[Invited talk: 17:15 – 17:45, Oct.30, 2018]

Origin of high thermoelectric performance in n- and p-type
SnSe crystals
Li Huang1,*
1

Department of Physics, Southern University of Science and Technology, Shenzhen
518055,China*

E-mail: huangl@sustc.edu.cn

Tin selenide (SnSe) has emerged as a very promising thermoelectric material due to its
record high figure of merit ZT for both n- and p-type crystals in mediate temperature
range. In this talk, I will present our recent works regarding its electronic and thermal
properties based on first-principles calculations, in combination with the Boltzman
transport theory and experimental measurements. The origins of strongly anisotropic
thermal and electrical behaviors in this layered lattice structure will be discussed, whichgive rise to the highest optimal ZT values along the a axis (out-of plane direction) in the
n-type SnSe, whereas along b axis in p-type materials. In addition, I will discuss theeffects of the intrinsic defects and dopants on its thermoelectric characteristics. Our
calculations show reasonable agreements with the experimental observations and provide
some guidance for optimizing the thermoelectric performance.

[Invited talk: 9:00 – 9:30, Oct.31, 2018]

Atom Dynamics in Solids Studied by Machine-Learning
Techniques
Satoshi Watanabe,1,2,* Wenwen Li,3 Yasunobu Ando,3 Takanori Moriya,1 Masayoshi
Ogura,1 Koji Shimizu,1 and Emi Minamitani1
1

Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo,
Bunkyo-ku, Tokyo 113-8656, Japan
2
Research and Services Division of Materials Data and Integrated System (MaDIS),
National Institute for Materials Science (NIMS), Tsukuba 305-0047, Japan
3

Research Center for Computational Design of Advanced Functional Materials, National
Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan*

E-mail: watanabe@cello.t.u-tokyo.ac.jp

Development of novel information and energy devices demands deeper understanding on
atom dynamics in solids, such as diffusion and vibration. First-principles calculations
within the density functional theroy (DFT) is powerful to meet the demand. In practice,
however, DFT often requires too heavy computations to tackle with atom dynamics insolids. In this context, interatomic potentials constructed with machine-learningtechnique and DFT calculation data have attracted much attention recently. In theprensent talk, we will describe our recent works on interatomic potentials constructedwith one of machine-learning techniques, neural network (NN).
Our NN potentials are based on the method proposed by Behler and Parrinello [1]. We
discuss NN potentials to examine diffusion behaviors of Cu in amorphous Ta2O5 [2]and Li in Li3PO4 [3]. The results agree well with DFT calculations, showing the highreliability of the constructed NN potentials. For Li in Li3PO4, the NN potential trained ina small supercell is successfully applied to calulations in much larger supercells, whichsuggests good transferability. We will also discuss (i) atom dynamics under electric fields,(ii) structures of metal/solid-electrolyte interfaces, and (iii) phonon bands and thermaltransport, with describing our prelimienary results.
Our works presented in this talk were supported in part by “Materials research by
Information Integration” Initiative (MI2I) project of the Support Program for Starting Up
Innovation Hub from Japan Science and Technology Agency (JST), CREST-JST, and
JSPS KAKENHI, Japan.
[1] J. Behler and M. Parrinello, Phys. Rev. Lett. 98, 146401 (2007).
[2] W. Li, Y. Ando, and S. Watanabe, J. Phys. Soc. Jpn. 86, 104004 (2017).
[3] W. Li, Y. Ando, E. Minamitani, and S. Watanabe, J. Chem. Phys. 147, 214106 (2017).

[Invited talk: 9:30 – 10:00, Oct.31, 2018]

TDDFT Study of Electron Scattering Processes
Yasumitsu Suzuki,1,* Lionel Lacombe,2 Kazuyuki Watanabe,1and Neepa T. Maitra2
1

Department of Physics, Tokyo University of Science,
1–3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan2
Department of Physics and Astronomy, Hunter College and the Graduate Center of
the City University of New York,695 Park Avenue, New York, New York 10065, USA*

E-mail: yasumitsu.suzuki@rs.tus.ac.jp

Time-dependent density functional theory (TDDFT) is the most widely used firstprinciples approach to study real-time many-electron dynamics. TDDFT withapproximate exchange-correlation (XC) potentilas has been successfully applied tointerpret and predict electron dynamics in a range of situations. Recently, it has been
applied to the real-time nonperturbative calculations of electron wave packet scatteringfrom atomic layer materials [1-5].
However, it is known that TDDFT with approximate XC potentials fails to evenqualitatively reproduce the true dynamics in some applications to nonlinear time-resolved
dynamics. In this study [6, 7], we address the question how accurate TDDFT with thecurrently available approximate XC potentials is for electron scattering. To this end, we
have studied model systems of electron-H and electron-He+ scattering that can beexactly solved numerically.
We have identified peak and valley structures in the exact XC potential that are crucial
for accurately capturing time-resolved dynamics of electron scattering [6, 7].
Approximate functionals used today miss these structures and consequently
underestimate the scattering probability. The dynamics can vary significantly dependingon the choice of the initial Kohn-Sham state. A recently propsed nonadiabatic
approximation is shown to correctly capture the approach of the electron to the target
when the initial Kohn-Sham state is chosen judiciously, and it is more accurate thanstandard adiabatic functionals but ultimately fails to accurately capture reflection. These
results may explain the underestimation of scattering probabilities in some recent studies
on molecules and surfaces.
[1] K. Tsubonoya, C. Hu, and K. Watanabe, Phys. Rev. B 90, 035416 (2014).
[2] Y. Ueda, Y. Suzuki, and K. Watanabe, Phys. Rev. B 94, 035403 (2016).
[3] H. Miyauchi, Y. Ueda, Y. Suzuki, and K. Watanabe, Phys. Rev. B 95, 125425 (2017).
[4] Y. Ueda, Y. Suzuki, and K. Watanabe, Phys. Rev. B 97, 075406 (2018).
[5] Y. Ueda, Y. Suzuki, and K. Watanabe, Appl. Phys. Express 11, 105101 (2018).
[6] Y. Suzuki, L. Lacombe, K. Watanabe, and N. T. Maitra, Phys. Rev. Lett. 119, 263401(2017).
[7] L. Lacombe, Y. Suzuki, K. Watanabe, and N. T. Maitra, Eur. Phys. J. B 91, 96 (2018).

[Invited talk: 10:00 – 10:30, Oct.31, 2018]

Band topologies and spin-phonon dynamics of spin-orbit
coupled insulators: a study with the real-time TDDFT
Noejung Park and Dongbin Shin

Department of Physics, Ulsan National Institute of Science and Technology, Ulsan, 689-798
Korea

Topological phases of solid-state bands have been widely examined in these days
condensed matter field, and global properties immune to local perturbations have been
explored as topologically non-trivial observables. The computations of topologicalquantities of real materials are affordable only through the theories of linear responses
over the static ground electronic structure. Here, we propose a conceptually novel andgeneral method: we perform the time evolution of the solid state, ψ , (𝑟⃗, 𝑡), through thetime-dependent Schrödinger equation, and calculate physical observables such as charge
current or spin current as an expectation evaluated from the time-evolving states functions.
We present exemplary cases of trivial insulator, a spin-frozen valley-Hall system, a spinfrozen Haldane-Chern insulator, and quantum spin-Hall insulators. The same real-time
dynamics is also used for the phonon-coupled spin dynamics of semiconductors withstrong spin-orbit coupling. We present that the spin precession dynamics of MoS2 inwhich the spin is strongly coupled to a specific optical phonon. This dynamical spin state
can be resolved into discrete Floquet-phononic spectra, and once the phonon is pumped
so as to break time-reversal symmetry, the resulting spin-Floquet structures induce net
out-of-plane magnetizations in the otherwise non-magnetic 2D material.

[Invited talk: 10:45 – 11:15, Oct.31, 2018]

Topological crystalline insulator: From symmetry indicators
to material discovery
Tay-Rong Chang,1* Hsin Lin,2 and Liang Fu3
1

Department of Physics, National Cheng Kung University, Tainan, 701, Taiwan
2
Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
3
Department of Physics, Massachusetts Institute of Technology, Cambridge,
Massachusetts 02139, USA*

E-mail: u32trc00@phys.ncku.edu.tw

Topological crystalline insulators (TCI) are insulating electronic phases of matter with
nontrivial topology originating from crystalline symmetries. In the past decade, many
materials have been demonstrated to be the topological insulators or the topologicalsemimetals, however the exotic TCI states have remained elusive. Building upon recent
theoretical works, we develop a feasible method to uniquely determine the novelrotational symmetry topological invariants based on first-principles calculations. In thistalk, I will show how we predict new TCI materials and display their unusual electronic
structures that entirely distinct from traditional topological materials [1].
[1] Xiaoting Zhou et al. Topological crystalline insulator states in the Ca2As family,
arXiv:1805.05215 (2018).

[Invited talk: 11:15 – 11:45, Oct.31, 2018]

Towards ideal topological materials: Comprehensive databasesearches using symmetry indicators
Feng Tang1,2, Hoi Chun Po3, Ashvin Vishwanath3, Xiangang Wan1,2*1National Laboratory of Solid State Microstructures and School of Physics, Nanjing
University, Nanjing 210093, China
2
Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
3
Department of Physics, Harvard University, Cambridge, MA 02138, USA*

E-mail: xgwan@nju.edu.cn

Topological materials (TMs) showcase intriguing physical properties defying
expectations based on conventional materials, and hold promise for the development ofdevices with new functionalities. While several theoretically proposed TMs have been
experimentally confirmed, extensive experimental exploration of topological properties
as well as applications in realistic devices have been held back due to the lack of excellent
TMs in which interference from trivial Fermi surface states is minimized. We tackle thisproblem in the present work by applying our recently developed method of symmetry
indicators to all non-magnetic compounds in the 230 space groups. An exhaustive
database search reveals thousands of TM candidates. Of these, we highlight the excellent
TMs, the 258 topological insulators and 165 topological crystalline insulators which have
either noticeable full band gap or a considerable direct gap together with small trivial
Fermi pockets. We also give a list of 489 topological semimetals with the band crossing
points located near the Fermi level. All predictions obtained through standard generalized
gradient approximation (GGA) calculations were cross-checked with the modified
Becke-Johnson (MBJ) potential calculations, appropriate for narrow gap materials. With
the electronic and optical behavior around the Fermi level dominated by the topologically
non-trivial bands, these newly found TMs candidates open wide possibilities for realizing
the promise of TMs in next-generation electronic devices.
[1] Feng Tang, Hoi Chun Po, Ashvin Vishwanath, Xiangang Wan, arXiv:1807.09744(2018).
[2] Feng Tang, Hoi Chun Po, Ashvin Vishwanath, Xiangang Wan, arXiv:1806.04128(2018).
[3] Feng Tang, Hoi Chun Po, Ashvin Vishwanath, Xiangang Wan, arXiv:1805.07314(2018).

[Invited talk: 11:45 – 12:15, Oct.31, 2018]

Topological Materials
Hsin Lin1,*
1

Institute of Physics, Academia Sinica, Taipei 11529, Taiwan*

E-mail: nilnish@gmail.com

Topological materials host various novel quantum phases of electrons which arecharacterized by band topology and topologically protected surface/edge states. [1]Despite recent progress, intense world-wide research activity in search of new classes of
topological materials is continuing unabated. This interest is driven by the need formaterials with greater structural flexibility and tunability to enable viable applications in
spintronics and quantum computing. We have used first-principles band theory
computations to successfully predict many new classes of 3D topologically interestingmaterials, including Bi2Se3 series, [2] the ternary half-Heusler compounds, [3] TlBiSe2
family, [4] Li2AgSb-class, and GeBi2Te4 family as well as topological crystalline
insulator (TCI) SnTe family [5] and Weyl semimetals TaAs, [6,7] SrSi2, [8](Mo,W)Te2, [9] Ta3S2, [10] and LaAlGe family. [11,12] I will also highlight our recent
work on unconventional chiral fermions in RhSi, [13] cubic Dirac points in LiOsO3, [14]and rotaional symmetry protected TCIs. [15][1]A. Bansil, H. Lin, and T. Das, Rev. Mod. Phys. 88, 021004 (2016).
[2]
Y. Xia, D. Qian, D. Hsieh, L. Wray, A. Pal, H. Lin, A. Bansil, D. Grauer, Y. S.
Hor, R. J. Cava, and M. Z. Hasan, Nat. Phys. 5, 398 (2009).
[3]
H. Lin, L. A. Wray, Y. Xia, S. Xu, S. Jia, R. J. Cava, A. Bansil, and M. Z. Hasan,
Nat. Mater. 9, 546 (2010).
[4]
H. Lin, R. S. Markiewicz, L. A. Wray, L. Fu, M. Z. Hasan, and A. Bansil, Phys.
Rev. Lett. 105, 036404 (2010).
[5]
T. H. Hsieh, H. Lin, J. Liu, W. Duan, A. Bansi, and L. Fu, Nat. Commun. 3, 982(2012).
[6]
S.-M. Huang et al. Nat. Commun. 6, 7373 (2015).
[7]
S.-Y. Xu et al. Science 349, 613 (2015).
[8]
S.-M. Huang et al. Proc. Natl. Acad. Sci. 113, 1180 (2016).
[9]
T.-R. Chang et al. Nat. Commun. 7, 10639 (2016).
[10]
G. Chang et al. Sci. Adv. 2, e1600295 (2016).
[11]
S.-Y. Xu et al. Sci. Adv. 3, e1603266 (2017).
[12]
G. Chang et al. Phys. Rev. B 97, 041104 (2018).
[13]
G. Chang et al. Phys. Rev. Lett. 119, 206401 (2017).
[14]
W. C. Yu et al. Phys. Rev. Mater. 2, 051201 (2018).
[15]
X. Zhou et al. ArXiv:1805.05215, Phys. Rev. B in press (2018).

Abstracts
Poster Presentations

Poster-1

Density functional study of phonon-induced photocarrier capture in
defective MoSe2
Soungmin Bae1 and Yong-Hoon Kim1,*
Graduate School of Energy, Environment, Water, and Sustainability, Korea
Advanced Institute of Scence and Technology (KAIST),
291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea*

E-mail address: y.h.kim@kaist.ac.kr

In recent years, optical electronic excitations and photocarrier dynamics in transition
metal dichalcogenides (TMDCs) have been actively investigated in view ofunderstanding photophysics in atomically thin materials and their optical device
applications. According to recent studies on pristine TMDCs, acoustic phonons are
involved in exciton generation and electron cooling processes [1,2]. In practical situations,
TMDC samples usually contain a certain amount of defects and adsorbates, which act as
ultrafast photocarrier trapping centers [3,4]. Meanwhile, although the exciton-phonon
interaction in pristine TMDC is relatively well studied, defect-related photocarrier
trappings remain vague.
Here, we present our theoretical study of defect-induced photocarrier capture in MoSe2
by means of delta-self-consistent-field (∆SCF) density functional theory calculations[5,6]. Starting from the ground-state MoSe2 with various defects, we explicitly minimize
the geometry of its excited states at defects, thus explicitly treating the nonradiative decay
through multi-phonon emission processes. Comparing our computational results withpump-probe measurement data, we conclude that the exciton trapping at a Se vacancy
adsorbed by an oxygen molecule is a dominant photocarrier capture mechanism.
[1] S. Shree, et al. Phys. Rev. B 98, 035302 (2018).
[2] C.M. Chow, et al. npj 2D Mater. Appl. 1, 33 (2017).
[3] K. Chen, et al. Adva. Mater. 28, 5293 (2016).
[4] H. Chuan, et al. ACS Appl. Mater. Interfaces 10, 1125-1131 (2018)[5] A. Gail, et al. Phys. Rev. B 80, 241204 (2009).
[6] A. Alkauskas, et al. J. Appl. Phys. 119, 18 (2016).

Poster-2

Poster-3

The Influence of Electron Correlation on the Electronic
Structure of Transition Metal Phthalocyanines
Iulia Emilia Brumboiu,1,2* Soumyajyoti Haldar,3 Johann Lüder,4 Heike C. Herper,5Olle Eriksson,5 Barbara Brena,5 and Biplab Sanyal5
1

Department of Chemistry, Korea Advanced Institute of Science and Technology(KAIST), 34141 Daejeon, Korea
2
Department of Theoretical Chemistry and Biology, KTH Royal Institute ofTechnology, 10691 Stockholm, Sweden
3
Institute of Theoretical Physics and Astrophysics, Christian-Albrechts-Universität
zu Kiel, 24098 Kiel, Germany
4
Department of Materials and Optoelectronic Science,National Sun Yat-Sen
University, 80424 Kaohsiung, Taiwan
5Department of Physics and Astronomy, Uppsala University, 75120 Uppsala,Sweden*E-mail: iubr@kth.se

Transition metal phthalocyanines (TMPcs) are highly symmetric organic molecules with atransition metal atom at their centre. TMPcs have been in the focus of scientific research as
possible candidates for applications in spintronics and molecular electronics, where the molecules
are typically used when adsorbed on various surfaces [1].
The study of properties of molecules adsorbed on substrates requires the availability of theoreticalmethods that are accurate enough, but which also have a relatively low computational cost.
From this point of view, the description of a TMPc adsorbed on a surface is not straightforward,
especially due to the presence of the metal d electrons. A compromise between accuracy andcomputational cost is achieved by combining Density Functional Theory (DFT) with a Hubbard
term exclusively acting on the correlated electrons. Many studies on TMPcs adsorbed on surfaces
make use of this approach, but the choice of U is mainly based on previously reported values for
similar systems. In this study [2], we provide a detailed analysis of the influence of U on theelectronic structure of five TMPcs (Mn-, Fe-,Co-, Ni- and CuPc).

By comparing the calculated valence electronic structures of the single molecules tophotoelectron spectroscopy experiments and by computing the Hubbard U term fromlinear response, we show that U is different for every phthalocyanine. For each TMPc,
we provide a range of U values that show good agreement with the experiments. These
values represent a safe starting point for DFT+U calculation of physisorbed TMPcs. By
calculating a multiple-site linear response U, we also show that the atoms covalently
bonded to the metal atom may influence the U value by as much as 1 eV. This point is
especially important when estimating the Hubbard U value for chemisorbed molecules.
[1][2]

L. Liu et al. Sci. Rep. 3, 1210 (2013).
I.E. Brumboiu, J. Chem. Theory Comput. 12, 1772 (2016).

Poster-4

Poster-5

Computational study of strain effect on the electronic
properties of Cu-doped CdSe nanoplatelets
SeongJae Byeon1, Yong-Hoon Kim1,*
1

School of Electrical Engineering, Korea Advanced Institute of Science and Technology(KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea*

E-mail: y.h.kim@kasit.ac.kr

Colloidal Copper-doped nanocrystals(NCs) such as CdSe and PbS NCs
is appealing due to their unique luminescence properties which are kwon tobroad and tunable photoluminescence(PL) via charge-transfer recombination of
conduction band electrons with copper localized holes. [1] However, to the bestof our knowledge, Cu-doped Nanoplatelets(NPLs) colloidal system have notbeen systemically studied yet. Herein, by means of density functional theory(DFT) calculation, we investigate the ground-states and excited-states geometry
and electronic properties of Cu+- and Cu2+-doped CdSe NPLs at the atomic level.
In particular, we focus on the strain effect on the electronic properties of Cu+and Cu2+-doped CdSe NPL capped with oleic acid organic ligand because
colloidal CdSe NPLs, experimentally, can be stressed by self-scrolled via crystal
growth. Our results showed that strain affects excited-state nuclear
reorganization, which is responsible for broad PL shape and large PL stokes shift.
We also computationally examined singlet and triplet excited-states
configuration. These calculations yield fundamental perspectives to understandstrain effect on electronic structure and photophysical properties of Cu-doped
NPLs.

[1] H. D. Nelson, S. O. M. Hinterding, R. Fainblat, S. E. Creutz, X. Li, and D.
R. Gamelin, J. Am. Chem. Soc. 139, 6411 (2017).

Poster-6

Energetics and optical properties of carbon impurities
in rutile TiO2
Supparat Charoenphon,1 Adisak Boonchun1,2, and Pakpoom Reunchan,1,2*
1

Department of Physics, Faculty of Science, Kasetsart University,
Bangkok 10900, Thailand
2
Thailand Center of Excellence in physics (ThEP Center), Commission on Higher
Education, Bangkok 10400, Thailand*

E-mail: pakpoom.r@ku.ac.th

Titanium dioxide (TiO2) is one of the most promising materials for many
applications such as solar-cell system and photocatalysis. Non-metal doping of TiO2 is
widely used to improve the photoconversion of the material by shifting the absorption
edge from UV to visible-light region [1, 2]. Here, we employ hybrid density-functional
calculations to investigate the energetics and electronic structures of carbon (C)impurities in rutile TiO2. The predominant configurations of C impurities under the Opoor and O-rich growth conditions are identified through the calculated formationenergies. Under the O-poor condition, we find the substitutional C occupying oxygen site(CO), as shown in FIG. 1, is energetically favorable for Fermi-level values near the
conduction band minimum (n-type TiO2) where it acts as double acceptor. On the other
hand, when Fermi-level positions decrease toward the valence band, C atoms favor toform the Ci-VO complex, as shown in FIG. 2, acting as sextuple donor. Under the O-richcondition, the Ci-VTi complex is found to be energetically favorable in n-type TiO2, andis exclusively stable in charge neutral. Our calculations based on the configuration
coordinated diagram suggest that CO is an origin of visible light absorbtion in n-type rutile
TiO2 fabricated under oxygen deflicient growth condition.

FIG. 1. (Color online) Local atomic
configuration of the substitutional C
occupying O site (CO) in rutile TiO2. The
substitutional C is indicated by the arrow.
[Ti: blue, O: red, C: dark brown].

FIG. 2. (Color online)
Local
atomic configuration of the Ci-VTi
complex. The interstitial C isindicated by the arrow.

[1] Asahi, R.; Morikawa, T.; Ohwaki, T.; Aoki, K.; Taga, Y. Science 2001, 293, 269.
[2] Khan, S. U. M.; Al-Shahry, M.; Ingler, W. B., Jr. Science 2002, 297, 2243.

Poster-7

Defect induced exciton states in transition metal
dichalcogenide WSe2 monolayer from first principles
Yifeng Chen1, Su Ying Quek1,2
1

Centre for Advanced 2D Materials and Graphene Research Centre, National
University of Singapore, 6 Science Drive 2, Singapore 117542, Singapore
2
Department of Physics, National University of Singapore, 2 Science Drive 3,
Singapore 117551, Singapore* E-mail: phyqsy@nus.edu.sgand

Recent intriguing optical phenomena such as single photon emitters, defect-boundexcitons, etc are observed in two dimensional transition metal dichalcogenide WSe2
monolayers. The nature of these exciton states are believed to be from either point defects
or strain. However, a clear understanding of the exact origin and the light-matterinteraction there is still lacking. The mostly abundant points defects in WSe2 were
believed to be Se vacancies. However, recent investigations from our group have shownthat oxygen molecules can dissociate easily at Se vacancy sites at room temperature,largely passivating these vacancies with oxygen atoms and eliminating the in-gap defectbands. Furthermore, the oxygen atom can diffuse into the WSe2 monolayer, forming aninterstitial point defect. The simulated scanning tunnelling microscopy (STM) images forthese defects agree well with recent experimental STM images at different bias voltages.
The next most favourable point defects are predicted to be Se/W antisites, under typicalSe-rich growth conditions. Here, using first principles density functional theory (DFT)
method and many body perturbation theory based GW-BSE (Bethe-Salpeter equation)
method, we investigate closely the implications of these three types of point defects (O/Se
substitution, O interstitials, Se/W antisites) on the optical response of monolayer WSe2.
Based on our findings, we propose that oxygen interstitial defects are the most likely
candidates for single photon emitters in WSe2 monolayer, while O/Se substitution defectdoes not induce additional exciton states below the pristine WSe2 A peak. Furthermore,spin-orbit splitting effects are considered to explain the experimentally observed multiple
peaks of single photon emitters with energies ranging 40~80 meV below the pristine A
peak. For Se/W antisites, a number of exciton states are found below the pristine A peak,with their emission properties determined by the relaxation dynamics. Overall, our firstprinciples results here provide crucial insights and understandings about these defectinduced exciton states in monolayer WSe2, and paves the way for further optoelectronic
and nanophotonic manipulation and device integration of these features in future studies.

Poster-8

Phonon-calculation validity of neural-network-potential
Young-Jae Choi and Seung-Hoon Jhi
Department of Physics, Pohang University of Science and Technology, Cheongam-ro
77, Pohang 37673, South Korea
jhish@postech.ac.kr
We are planning to study the dynamical instability of the phase change material in theamorphous state by analyzing the characteristics of the vibrational frequencies. It isdifficult to calculate with DFT because of large computational costs. Alternatively,
Behler's neural network potential (NNP) can compute at much faster speeds withcomparable accuracy to DFT calculations. [1] However, my current studies are showingthat the force calculation using conventional NNP lacks the accuracy to calculate thevibrational frequencies of the amorphous solid. Therefore, it is essential to develop a new
NNP descriptor prior to the following amorphous-solid-research. In this study, we havechecked the validity of the existing Behler NNP for calculating various physicalproperties.
[1] J. Behler, M. Parrinello, Phys. Rev. Lett. 98, 146401 (2007).

Poster-9

Emergence of Out-plane Ferroelectricity in Atomically Thin
A0.5B0.5X2 (A=W, Mo; B=Re, Tc; X=S, Se, Te) Monolayer
Ji-Hae Choi and Seung-Hoon Jhi
Department of Physics, Pohang University of Science and Technology (POSTECH),
77, Cheongam-ro, Pohang, Korea*

E-mail: seunghoonjhi@gmail.com

Atomically thin out-plane ferroelectricity is rare phenomena because its depolarization
field increases as thickness decreases. Using density functional theory, we found outplane polarization in transition metal dichalcogenides (TMDCs) with 1:1 composition of
VIB and VIIB transition metal. The magnitude of the polarization is ~ 0.08 μC/cm2, whichis comparable to the other reported atomically thin ferroelectric materials like distorted
1T-MoS2 or AgBiP2Se6 [1]. Interestingly, the polarization is in the opposite direction of
the point charge (ionic or Bader charge) approximation, implying unique distribution ofelectron density in these materials, like counterintuitive Born effective charge reported inother TMDCs [2].
[1] Bo Xu et al. Nanoscale 9, 8427 (2017).
[2] Nicholas A. Pike et al. Phys. Rev. B 95, 201106 (2017).

Poster-10

Excited electron dynamics in the 1T/2H heterophase ofmonolayer MoS2: Real-time time dependent density
functional theory study for photo-catalyst application
Min Choi1, 2, Jino Im2, Hyun Woo Kim2, Hyunju Chang2, and Noejung Park3
1

Department of Molecular Science, Ulsan National Institute of Science and Technology(UNIST),
Ulsan 689-798, South Korea
2
Korea Research Institute of Chemical Technology (KRICT),
Daejeon 34114, South Korea
3
Department of Physics, Ulsan National Institute of Science and Technology (UNIST),
Ulsan 689-798, South Korea
M.P.: +82-10-7674-3211 E-mail address: noejung@unist.ac.kr

Monolayer MoS2, one of the two-dimensional transition metal dichalcogenide (TMD)
materials, has two different phases, 2H and 1T phases. The 2H, the stable phase, is asemiconductor with direct band gap about 2.4 eV, and 1T, the meta-stable phase, has
metallic phase. The 2H phase of MoS2 has been studied and utilized as a hydrogen
evolution reaction (HER) catalyst because of its photovoltaic and photo-catalytic features.
On the other hand, the 1T phase of MoS2 has been investigated in the perspective ofnanoscale electronic device, such as ultrathin transistor and supercapacitor electrodecomponent. Furthermore, the heterophase boundary of 2H and 1T phases was alsosynthesized and its microscopic dynamics was investigated in terms of phase boundaryor phase transition.
In this study, we investigated geometric and electronic structure of the MoS2
heterophase. We found that two different types of phase boundary lead to difference inthe band alignments at MoS2 phase boundaries. As a consequence, the excited electrons
in the 2H phase region are transferred and accumulated in the 1T phase region, leading to
the charging of the 1T phase region. We performed the real-time time dependent density
functional theory (rt-TDDFT) calculation for this electron dynamics. We found that, as
the 1T phase is charged, the activation barrier of dissociative adsorption of oxygen
molecule on the planar surface of 1T phase is decreased. In the acidic condition, theoxygen reduction reaction (ORR) energy profile on the charged 1T phase region shows
similar electrochemical properties with that on the platinum (100) surface. We suggestthat the MoS2 heterophase can serve as the novel low-dimensional ORR photo-catalyst.

Poster-11

Structural relaxation, electronic structure, and electronphonon coupling in magic-angle twisted bilayer graphene
Young Woo Choi and Hyoung Joon Choi*
Department of Physics, Yonsei University, Seoul 03722, Korea*

E-mail: h.j.choi@yonsei.ac.kr

Interplay between the interlayer coupling and the rotational mismatch between two
graphene layers results in flattening of Dirac cones at certain special twist angles,
called magic angles. Recently, correlated insulator behavior and superconductivity wereexperimentally observed near the first magic angle, demonstrating rich
physics induced by the presence of the flat bands. In this regard, more detailed
characterizations for the magic-angle twisted bilayer graphene (MA-TBG) are being done.
In this poster, we investigate structural relaxations, electronic structure, electron-phonon
coupling in MA-TBG at the atomistic level. First, equilibrium atomic positions are
determined by minimizing the total energy of the system, consisting of the in-plane strainenergy and the interlayer binding energy. Then, we calculate the electronic structure andphonon spectrum using the tight-binding approach and the force constants, respectively.
The electron-phonon matrix elements are then obtained from the modulation of hopping
parameters due to atomic displacements of phonon modes. We present the electronphonon coupling strength in MA-TBG withas a function of doping level,and discuss implications for superconductivity in this system.
This work was supported by NRF of Korea (Grant No. 2011-0018306) and KISTI
supercomputing center (Project No. KSC-2017-C3-0079). Y.W.C. acknowledges support
from NRF of Korea (Global Ph.D. Fellowship Program NRF-2017H1A2A1042152).

Poster-12

Poster-13

The structural and electronic properties of Mo6S3I6nanowires by theoretical compositional arrangement
You Kyoung Chung1, Weon-gyu Lee1, Sudong Chae2, Jae-Young Choi2,3,* andJoonsuk Huh1,*,1

Department of Chemistry, Sungkyunkwan University, Korea
School of Advanced Materials Science & Engineering, Sungkyunkwan University,
Korea
3
SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University,
Korea
2

*

E-mail: jy.choi@skku.edu, joonsukhuh@skku.edu

The structural, electronic, magnetic properties of molybdenum-based nanowires havebeen actively investigated for their potential applications as nanodevices; but further
developments are retarded due to the lack of knowledge on the exact electronic andatomic structures of Mo6S3I6. For further development of Mo6S3I6 nanowire devices, we
propose possible atomic structures and the corresponding electronic properties of Mo6S3I6nanowires based on our density functional theory calculations. We scanned various
combinations of atomic structures by changing the decorative positions of sulfur andiodine linked to two Mo6 octahedral. As a result, we found two stable local energy
minimum structures characterized by elongation of S3 linkage; and propose, based on thetwo stable structures, possible structures of twenty-eight atomic models according to thesulfur saturation in bridging plane. We calculated band structures of the newly proposed
atomic models and finally found three atomic models of conductors. According to ourcompositional ordering structural analysis, we concluded (i) periodic distortion of thebond lengths influences the behavior of the electrons in a system, (ii) role of sulfur atoms
in bridging plane is important for intramolecular charge transport by the delocalized
charge differences, and (iii) electronic band gap energy is proportional to the integrated
Mo-S bonding orbital energy.

Poster-14

First-principles Calculations of Stacking Stability of C2N
Bilayer Nanosheet
Klichchupong Dabsamut,1 Sirichok Jungthawan,2,3 and Adisak Boonchun1,2*
1

Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900,
Thailand.
2
School of Physics, Institute of Science, Suranaree University of Technology,
Nakhon Ratchasima 30000, Thailand.
3
Thailand Center of Excellence in Physics, Commission on the Higher Education,
328 Si Ayutthaya Road, Bangkok 10400, Thailand*

E-mail: adisak.bo@ku.th, fsciasb@ku.ac.th

In recent years, a 2D graphene-like sheet: monolayer C2N was synthesized via a
simple wetchemical reaction [1]. Here, we study the stability and electronic properties ofbilayer C2N. According to previous a study, a bilayer may exist in one of three highly
symmetric stacking configurations, namely as AA, AB and AB’-stacking [2]. For the AAstacking, the top layer is directly stacked on the bottom layer. Furthermore, AB- and AB’stacking can be obtained by shifting the top layer of AA-stacking by a/3-b/3 along zigzag
direction and by a/2 along armchair direction, respectively, where a and b are translation
vectors of the unit cell. By using first-principles calculations, we calculated the stabilityof AA, AB and AB’-stacking C2N and their electronic band structure. In previous result,the most favourable structure is AB-stacking. In present work, we furthermore examinedthe energy landscape and translation sliding barriers between stacking layers. Fromenergy profiles, we interestingly found that the most stable positions are shifted from thehigh symmetry AB-stacking. In electronic band structure details, band characteristic canbe modified according to the shift.

Fig 1. 2D-energy profile surface of bilayer C2N depending on the inter-layer relative slide distance(ΔX, ΔY).

[1] J. Mahmood, E. K. Lee, M. Jung, D. Shin, I.-Y. Jeon, S.-M. Jung, H.-J. Choi, J.-M.
Seo, S.-Y. Bae and S.-D. Sohn, Nature communications 6, 6486 (2015).
[2] R. Zhang, B. Li and J. Yang, Nanoscale 7 (33), 14062-14070 (2015).

Poster-15

Standard model of the Rare-Earths analyzed from the
Hubbard I approximation
I. L. M. Locht,1,2 Y. O. Kvashnin,1 D. C. M. Rodrigues,1,3 M. Pereiro,1 A. Bergman,1
L. Bergqvist,4,5 A. I. Lichtenstein,6 M. I. Katsnelson,2 A. Delin,1,4,5 A. B. Klautau,3 B.
Johansson,1,7 O. Eriksson1 and I. Di Marco,1,8,*
1Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20
Uppsala, Sweden
2
Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135,
6525 AJ Nijmegen, the Netherlands
3
Faculdade de Fı́sica, Universidade Federal do Pará, Belém, Pará, Brazil
4
Department of Materials and Nanophysics, School of Information andCommunication Technology, Electrum 229,
Royal Institute of Technology (KTH), SE-164 40 Kista, Sweden
5
Swedish e-Science Research Centre (SeRC), KTH Royal Institute of Technology,
SE-100 44 Stockholm, Sweden
6
Hamburg University, Institute for Theoretical Physics, D-20355 Hamburg,
Germany
7
Department of Material Science and Engineering, KTH Royal Institute ofTechnology, Stockholm SE-100 44, Sweden
8
Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784, Korea*

E-mail: igor.dimarco@apctp.org

In this poster we examine critically the electronic structure of the rare-earth elements byuse of the so-called Hubbard I approximation [1]. From the theoretical side all measured
features of both occupied and unoccupied states are reproduced, without significant
deviations between observations and theory. We also examine cohesive properties likethe equilibrium volume and bulk modulus, where we find, in general, a good agreement
between theory and measurements. In addition, we have reproduced the spin and orbital
moments of these elements as they are reflected from measurements of the saturation
moment. We have also employed the Hubbard I approximation to extract the interatomic
exchange parameters of an effective spin Hamiltonian for the heavy rare earths. We showthat the Hubbard I approximation gives results which are consistent with calculations
where 4f electrons are treated as core states for Gd. The latter approach was also used toaddress the series of the heavy/late rare earths. Via Monte Carlo simulations we obtainedordering temperatures which reproduce measurements within about 20%. We havefurther illustrated the accuracy of these exchange parameters by comparing measured andcalculated magnetic configurations for the heavy rare earths and the magnon dispersion
for Gd.
[1]

I. Locht et al. Phys. Rev. B 94, 085137 (2016).

Poster-16

DFT+DMFT study of phase transitions with a large volume
collapse in MnSe under pressure
Alexey A. Dyachenko,1,* Alexey V. Lukoyanov,1,2 Alexey O. Shorikov,1,2 andVladimir I. Anisimov1,2
1

M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of
Sciences, 620108 Yekaterinburg, Russia
2
Ural Federal University, 620002 Yekaterinburg, Russia*

E-mail: dyachenko@imp.uran.ru

Manganese selenide is known to undergo the phase transition from cubic NaCl-type toorthorhombic MnP-type B31 (Pnma) with the large volume collapse of about 22% in theregion of 20-30 GPa with an unknown tetrahedral phase in between and a metallization
at 25 GPa [1]. We present a DFT+DMFT study of spectral, magnetic, and structuralproperties of the manganese selenide under pressure [2]. Our calculations reveal that ahigh-spin to low-spin transition occurs upon compression at volumes below 33 Å3. The
spin-state transition is accompanied by a metal-insulator transition and a structural phasetransition with the large volume collapse of ∼20% from the cubic B1 structure to thehigh-pressure MnP-type B31 structure at about 27 Å3. We find that the spin-statetransition is the main driving force for the structural transition in MnSe under pressure.

Figure 1: Calculated within the DFT+DMFT method Mn-3d spectral
functions at 1000 K of the manganese selenide MnSe at ambient pressure(left) and after the volume collapse under pressure (right).

[1]
[2]

Y. Wang et al. Angew. Chem. Int. Ed. 55, 10350 (2016).
A. A. Dyachenko et al. Phys. Rev. B 98, 085139 (2018).

Poster-17

First-Principles Study on Electron Transport Properties of
Halogenated Graphene
Yoshiyuki Egami1 and Masahiro Kudo2
1

Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, Japan
School of Engineering, Hokkaido University, Sapporo, Hokkaido, Japan2*

E-mail: y_egami@eng.hokudai.ac.jp

Recently, an electronic device constructed from a graphene has been investigatedextensively and has been expected to be a candidate for replacing silicon-based devices
owing to several unique properties of the graphene (rapid electron transfer, good thermal
conductivity, and splendid flexibility). A lot of experimental and theoretical studies on
physical functionalizations and chemical modifications of graphene for tuning theseproperties have been performed. A chemical adsorption of atoms and molecules on thegraphene surface is one of important modifications. In particular, a halogen adatom X(X=F, Cl, Br, and I) can change the atomic and electronic structures of the grapehen
drastically, where the formation of C-X covalent bonds is accompanied by sp2 to sp3
structural transition of C-C bonds (Fig. 1).
In this work, the electron transport properties of the halogenated graphene areinvestigated. Here, we performed the molecular dynamics calculations to determine afully-relaxed atomic geometry of halogenated graphene using the RSPACE code[1],which is based on the real-space finite difference approach within a framework of thedensity functional theory. Moreover, we curried out the electron transport simulations[2]to estimate the dependence of the electric conductivity and the spatial path of current flowon the coordinates and species of adsorbed halogen atoms. The details of this work arepresented at the workshop.

Fig. 1: Schematic view of a halogenated graphene. There are six halogen atoms(green spheres) and each atom form a covalent bond with a carbon atom (greyspheres).

[1] K. Hirose, T. Ono and Y. Fujimoto, and S. Tsukamoto, First-Principles
Calculations in Real-Space Formalism, (Imperial College Press, London, 2005).
[2] Y. Egami, K. Hirose, T. Ono, Phys. Rev. E 82, 056706 (2010); Y. Egami, S. Iwase,
S. Tsukamoto, T. Ono, K. Hirose, Phys. Rev. E 92, 033301 (2015).

Poster-18

Predicting topological insulators in hydrogenated transition
metal dichalcogenide monolayers: A first-principles study
Liang-Ying Feng1, Harvey N. Cruzado1, Rovi Angelo B. Villaos1,
Zhi-Quan Huang1, Hung-Chung Hsueh2, Hsin Lin3, Feng-Chuan Chuang1,*
1

Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan
2
Department of Physics, Tamkang University, Taipei, Taiwan
3
Institute of Physics, Academia Sinica, Taipei, Taiwan*

E-mail: fchuang@mail.nsysu.edu.tw

Two dimensional (2D) transition metal dichalcogenides (TMD) monolayers havecurrently been of immense interest in materials research because of their versatility andtunable electronic properties. In this study, we perform systematically the first-principles
calculations of possible topological insulator phases on 1T and 2H MX2 monolayers, aswell as the effects of hydrogenation on one or both sides of the films. With regards tostructural stability, we find that Group IV(Ti, Zr, Hf)-, VI(Cr, Mo, W)-, and X(Ni, Pd,Pt)-based TMDs, respectively, adopted 1T, 2H, and 1T as their stable structures forunhydrogenated cases. However, upon hydrogenation, we observe structural phasetransition from 1T to 2H for Group IV, and from 2H to 1T for Group VI, and notransition was observed for Group X. We find that for 2H TiTe2 and 1T CrTe2 with 1hydrogen, as well as 2H PdSe2 without hydrogenation, are identified to be topologicalinsulators with large band gaps of 0.07eV, 0.21eV and 0.23eV, respectively. Thesefindings show that these TMDs in quantum spin Hall phase have a great potential for
spintronics applications.

Poster-19

Structure exploration for AB2 type monolayers
by high-throughput DFT calculations
Masahiro Fukuda,1 Jingning Zhang2 and Taisuke Ozaki1
1

2

Institute for Solid State Physics, University of Tokyo, Chiba, Japan
Department of Physics, University of Science and Technology of China, Hefei, China
Contact: masahiro.fukuda@issp.u-tokyo.ac.jp

Two-dimensional (2D) monolayers have attracted incredible interest because of theirpeculiarities and novel properties. For example, graphene and silicene are well known asatomically thin monolayers. Boron nitride and silicon carbide are known as AB typemonolayers. In addition, various kinds of monolayers of transion metal (A=Mo, W, etc.)
dichalcogenides (B=S, Se or Te) with a formula AB2, which are arranged in triatomic
layers, have been recently synthesized experimentally for producing a AB2 type 2Dtransition metal chalcogenide library [1]. These kinds of investigations have revealed
interesting phenomena such as two-demensional superconductivity and quantum spin
Hall effect. However, it can be considered that several kinds of 2D structures which canexist stably may have not been synthesized experimentally yet since the combination of
the elements is diverse even only for the AB2 composition. Therefore, there is a room for
exploring unknown monolayers.
In this study, we performed high-throughput calculations based on the density
functional theory by using OpenMX[2] to create a structure map for AB2 type monolayers.
At first, we categorized the AB2 structures into planar, 1T (trigonal) phase (ex. ZrS2 [1]),2H (hexagonal) phase (ex. MoS2 [1]), memory structure and the others. Here, the groupof “planar” means B atoms form almost honeycomb structures and A atoms are on thecenter of the honeycombs. The group of “memory structure” means that the structure issimilar to the planar, but A atoms are shifted from the plane formed by B atoms. Since
the positions (up or down) of A atoms can represent binary digits, we call the backled
structures “memory structure” here. This structure can be a candidate for a data strage
application with an extremely high areal density. Next, we prepared 2×2 supercell AB2
initial structures (1T, 2H and planar) for selected compounds (62 elements × 62
elements=3844 compounds), where compounds of noble gases, lanthanides and actinides
are excluded. After geometry relaxations and variable cell optimizations were carried out,
the most stable converged structures were summarized on the structure map for AB2 typemonolayers.
From the structure map, we predicted that some of the structures can be the memory
structure. Some NEB calculations for these memory structures indicate that it may bepossible to control them as binary digits strage applications. In this presentation, we report
the details of the high-throughput calculations and show some obtained interesting
structures.
[1] J. Zhou et al. Nature 556, 355 (2018).
[2] OpenMX, http://www.openmx-square.org/.

Poster-20

Poster-21

Intermediate-phase Method for Computing the Natural Band
Offset between Two Materials with Dissimilar Structures
Hui-Jun Gu1,2, Yue-Yu Zhang1,2, Shi-You Chen3, Hong-Jun Xiang1,2, and Xin-Gao
Gong1,2,*
1

Key Laboratory for Computational Physical Sciences (MOE), State Key Laboratory of Surface
Physics, Department of Physics, Fudan University, Shanghai 200433, China
2
Collaborative Innovation Center of Advanced Microstructures, Nanjing, 210093, China
3
Key Laboratory of Polar Materials and Devices (MOE), East China Normal University,
Shanghai 200241, China*E-mail: xggong@fudan.edu.cn

The band offset between different semiconductors is an important physical quantity
determining carrier transport properties near the interface in heterostructure devices.
Computation of the natural band offset is a longstanding challenge. We propose anintermediate-phase method to predict the natural band offset between two structures withdifferent symmetry, for which the superlattice model cannot be directly constructed. With
this method, and the intermediate phases obtained by our searching algorithm, we
successfully calculate the natural band offsets for two representative systems, (i) zincblende CdTe and wurtzite CdS and (ii) diamond and graphite. The calculation shows thatthe valence band maximum (VBM) of zinc-blende CdTe lies 0.71 eV above that ofwurtzite CdS, close to the result 0.76 eV obtained by the three-step method. For thenatural band offset between diamond and graphite which could not be computed reliably
with any superlattice methods, our calculation shows that the Fermi level of graphite lies
1.51 eV above the VBM of diamond using a newly identified intermediate phase. Thismethod, under the assumption that the transitivity rule is valid, can be used to calculate
the band offsets between any semiconductors with different symmetry on condition thatthe intermediate phase is reasonably designed.[1][1] H. J. Gu, Y. Y. Zhang, S. Y. Chen, H. J. Xiang, and X. G. Gong, Phys. Rev. B 97, 235308 (2018)

Poster-22

Theoretical study on positronium formation at metal surfaces
based on two-component density functonal theory
Satoshi Hagiwara*, and Atsuo Kawasuso
National Institutes for Quantum and Radiological Science and Technology,
1233 Watanuki, Takasaki, Gunma 370-1292, Japan.
*

E-mail: hagiwara.satoshi@qst.go.jp

When positrons are slowly incident onto the material surfaces, a portion of thepositrons diffuse back to the surface. Then, positronium (Ps), which is a bound state
between an electron and a positron, is formed and spontaneously emitted into the vacuum,
when its work function is negative [1]. Since normally Ps is not formed in the bulk due
to the strong electron screening effect to positrons, the Ps formation spectroscopy has
been expected to be a sensitive probe for the surface electronic structures. In this respect,
Ps formation processes at various surfaces have been studied both theoretically [2] andexperimentally [3].
Recently, an experiment using spin-dependent Ps formation and annihilation, has been
carried out to investigate the surface spin-polarization of ferromagnetic surfaces covered
with graphene and boron-nitride white graphene (BNWG) [4]. This study demonstrated
that the Ps is formed at the first surface layer (i.e., graphene or BNWG), and the surface
spin-polarization is caused by orbital hybridization between the ferromagnets andgraphene or BNWG. This finding implies the potential of Ps formation spectroscopy indetermining the surface electronic structure at the first atomic layer.
However, the details of the Ps formation at surface have not yet been fully understoodbecause of the lack of theoretical study on the Ps formation using real material surfaces.
Previous theoretical studies on the Ps formation were carried out within a jellium modelor by assuming bulk electronic band structures [2]. In order to understand the Ps
formation mechanism precisely, we are conducting the calculation of two-component
density functional theory (TCDFT) for the Ps formation energy spectrum (PsFES) at
metal surfaces. TCDFT is the one of the most flexible and powerful tool to study
electronic and positronic states in real materials [5].
We found that the calculated PsFES qualitatively reproduce the experimental data. We
also examined the projections of PsFES to the surface electronic band structures.
Consequently, we found that the PsFES significantly depends on surface electronic states.
In the presentation, we will report further details of the Ps formation processes.
[1] C. Hugenschmidt, Surf. Sci. Rep. 71, 547 (2016).
[2] A. Ishii Surf. Sci. 209, 23 (1989).
[3] A. Jones et al. Phys. Rev. Lett. 117, 216402 (2016).

[4] A. Miyashita et al. Phys. Rev. B 97, 195405 (2018).
[5] M. Puska and R. Nieminen Rev. Mod. Phys. 66, 841 (1994).

Poster-23

A hybrid approach combining artificial neural network
potentials with first-principles calculations
Woo Hyun Han,1* In-Ho Lee,2 and Kee Joo Chang1
1

Department of Physics, Korea Advanced Institute of Science and Technology,
Daejeon 34141, Korea
2
Korea Research Institute of Standards and Science, Daejeon 34113, Korea*

E-mail: hanwooh@kaist.ac.kr

Constructing accurate potential-energy surfaces (PES) as a function of atomic position
is an important subject in both condensed matter physics and materials science to performreliable atomic simulations. Recently, artificial neural networks (ANN) have beensuggested to be a promising technique for constructing the PES of complicated systems.
Reliable ANN potentials have several advantages in terms of efficiency and accuracy
compared with other interatomic potentials and can replace first-principles calculations
for crystal structure serach in which a vast number of configurations should be optimized
to find the global mininum. However, for successful application of ANN potentials to
crystal structure serach, improving its accuaracy and choosing proper training sets remaina challenging issue to overcome.
In this work, we propose a hybrid approach combining ANN atomic potentials with
first-principles calculations, which improves the efficiency of crystal structure search. We
generate high-dimensional ANN potentials for Si using the Behler-Parrinello approach.
The weight parameters for the ANN potentials are optimized by using the machinelearning technique. For applications to crystal structure search, these ANN potentials are
combined with the conformational space annealing algorithm for global optimization. In
each generation, we employ the so-called self-learning training in which configurations
generated by the conformational space annealing algorithm are used as training sets.
Although the self-learning ANN potentials cover a varierty of structures, the accuracy ofthese potentials is still not sufficient to perform the local energy minimization. To remove
the residual forces and stresses, first-principles calcualtions are additionally performed
for low-energy configurations prior to sorting configurations for the next generation. Our
results show that ANN potentials can be used as an efficient local minizer with the helpof first-principles calculations, greatly improving the crystal structure search for the
stable as well as diverse metastable phases with reduced computational costs.

Poster-24

Phase Diagram of Ga(As,Sb) and (In,Ga)Asby Cluster Expansion and DFT Calculations
Gyuseung Han,1,2 In Won Yeo,1,2 Seung Cheol Lee3, Cheol Seong Hwang1 andJung-Hae Choi2,*
1

Center for Electronic Materials, Korea Institute of Science and Technology, Seoul
02792, Korea
2
Department of Materials Science and Engineering, and Inter-university
Semiconductor Research Center, Seoul National University, Seoul 08826, Korea
3
Indo-Korea Science and Technology Center, Bengaluru 560065, India*

E-mail: choijh@kist.re.kr

A solid solution is a chemical mixture of several components and forms a single phase ina certain range of composition. For a given composition of a solid solution, tremendous
number of atomic cofigurations are possible and properties of a solid solution depend on
the configuration [1][2]. Therefore, it is practically impossible to calculate the all possible
configurations by DFT calculations. On the other hand, materials properties come fromthe interaction between atoms, and the properties of materials can be interpreted as thesum of the contribution of interactions of some atomic groups, which are called clusters.
Cluster expansion method predicts the properties of any atomic configuration by
calculating the contribution of each interaction on properties [3]. Predicted properties ofeach configuration are combined into properties of materials by the grand canonicalensemble.
In this study, the phase diagrams of Ga(As,Sb) and (In,Ga)As are calculated by the
combined methods using ab-initio calculation, cluster expansion, canonical ensemble andgrand canonical ensemble. Although Ga(As,Sb) and (In,Ga)As systems have been studied
as one of the promising next-generation semiconductor channel materials, experimental
studies on the phase diagram of (In,Ga)As have been rare [4] and the those on Ga(As,Sb)
show ambiguous results [5][6]. we provide the phase diagrams of Ga(As,Sb) and(In,Ga)As phase and compare them with the previous experimental and theoreticalresults.
[1] Am. J. Opt. Photonics 4, 4 (2016).
[2] Nano Lett. 14, 455 (2008).
[3] J.M. Sanchez, F. Ducastelle, and D. Gratias, Phys. A, 128, 1-2 (1984).
[4] J.-Y. Shen, C.Chatillon, I. Ansara, A. Watson, B. Rugg, and T. Chart, Calphad 19, 2(1995).
[5] K. Ishida, T. Shumiya, T. Nomura, H. Ohtani, T. Nishizawa, J. Less-Common met.,
142 (1988).
[6] H. Mani, A. Joullie, F. Karouta, C. Schiller, Jour. Appl. Phys. 59, 2728 (1986).

Poster-25

Water droplet affects charge distribution of carbon nanotube
Koki Harada1, Kenji Sasaoka2, Takahiro Yamamoto1,2
1
2

Department of Electrical Engineering, Tokyo University of Science, Tokyo 125-8585, Japan
Water Frontier Science & Technology Research Center, RIST, Tokyo University of Science,
Tokyo 125-8585, Japan*

E-mail: 4317656@ed.tus.ac.jp

Water can be found on varius material surfaces in nanometer scale layer in ambient air.
This water layer often affect material surface propertes such as friction and adhension
force, chemical reactivity or electrical conductivity onsurface.
With it’s large surface area, carbon nanotube (CNT) is good material to resurch surface.
CNT films are highly responsive, so they expected as promising materials for highsensitivity gas sensors. When CNT film gas sensors are used for NO2 or formaldehyde,
the response to water vapor is obstacle. Therefore, understanding the mechanism andmagnitude of influence of water vapor on CNT films is needed to develop high accuracy
CNT sensors. Although it is believed that the conductance change is primally caused by
the charge transfer from water to CNTs, there is no carrier doping with simple
physisorption of H2O molecule in first-principles calculations [1]. The key is electrostaticinteraction between water and CNT which was recently reported [2].
We consider that water molecules adsorbed on CNT do not donate holes or electrons, butthey induce charge fluctuation in a CNT due to the electrostatic interaction between them.
In this work, we investigated the charge fluctuation in a CNT with water droplet (Fig.1)
using the first-principles simulation combined with the molecular dynamics simulation.
We found the hole concentration in carbon atoms close to water droplet and the electron
concentration in carbon atoms on the side of the droplet. This indicates a water droplet
induces charge and opposite carriers electrostatically shield around the droplet. We also
investigated the electronic transport in a water droplet absorbed CNT. We show that thewater droplet significantly reduces the electronic conductance of a CNT and influenceson the performance of CNT gas sensors.

Fig. 1. Snap shot of a water-droplet-absorbed CNT in molecular dynamics simulation

[1]
[2]

D. Sung, et al. Appl, Phys. Lett. 89, 243110 (2006).
D. Iwasaki, Y. Suzuki and K. Watanabe, Appl. Phys. Exp. 10., 045101 (2017).

Poster-26

Swarm-Intelligence Guided Computational Design of Novel
Silicon Allotropes
Xin He,1 and Lijun Zhang1,*
1

School of Materials Science and Engineering, Jilin University, Changchun 130012,
China*

E-mail for correspondence: lijun_zhang@jlu.edu.cn

Silicon (Si) in diamond structure is the most important material in current electronic andoptoelectronic technology. There has been considerable interest to find other Si allotropes
in different structures that have new properties for alternative applications. The
discovered allotropes include graphene-like hexagonal puckered silicene, and limited
metastable phases at high pressures. Besides the elementary phase, one can explore theidea of “Zintl-phase” compound and seek for Si allotropes in the compounds formed bysilicon and active metals (alkali or alkali earth ones). The large electronegativity
difference between Si and metals in Zintl-phase compounds leads to a nearly complete
electron transfer and to the formation of strong covalent bonds stabilizing the‘polyanionic motifs of Si’. Along this direction, the novel Si phases (for instance Si24)[1]
has been discovered by involving alkali metals, and silicene has been synthesized byusing the Zintl phase CaSi2.[2,3] In this work, we reported via swarm-intelligence guided
global structures search two never-before-reported novel silicon allotropes in the Zintlphase Ba-Si systems.
They are Ba2Si3 and Ba4Si5. The silicon structure in Ba2Si3 is composed of the exotic
hexagonal Si rings (resemblying the ‘planar’ Cyclopentasilane) that connect along one
direction to form one-dimensional chain-like structure. Ba4Si5 shows also a onedimensional silicon sublattice where three Si atoms assemble in triangle clusters
accompanying with a two-Si tail. The stability of the two Si allotropes was evidenced by
the energetic convex hull and phonon stability calculations. Their electronic structure,properties, and potential applications were discussed.[4]References:[1] D.Y. Kim, S. Stefanoski, O.O. Kurakevych, and T.A. Strobel, Nature Materials 14, 169 (2015).
[2] J. Zhuang, X. Xu, G. Peleckis, W. Hao, S.X. Dou, and Y. Du, Adv. Mater. 29, 1606716 (2017).
[3] U. Dettlaff-Weglikowska, W. Hönle, A. Molassioti-Dohms, S. Finkbeiner, and J. Weber, Phys.
Rev. B 56, 13132 (1997).
[4] X. He, L. Zhang, et al. submitted.

Poster-27

A first-principles study on the magnetism of
Fe/Bi/MgO multilayers
K. Hiraoka* and T. Oguchi
ISIR-SANKEN, Osaka University, Japan*

E-mail: hiraoka@cmp.sanken.osaka-u.ac.jp

The magnetic tunnel junction (MTJ) has a structure consisting of two ferromagnetic
layers separated by a thin insulating layer. MTJ is used for the magnetoresistive random
access memory (MRAM) cell with giant magneto resistance ratio. MRAM is anonvolatile memory without requiring standby power to keep information and has
attracted much attention as a new generation of low power consumption memory. Strong
perpendicular magnetic anisotropy to realize high density memory devices is highy
desired for preventing thermal magnetic fluctuation in the ferromagnetic layer of MTJ.
Perpendicular magnetic anisotropy originates from magnetocrystalline anisotropy(MCA) caused by spin-orbit coupling. In this study, we investigate the influence of a Bi
layer insertion at Fe/MgO interface by first-principles density-functional calculations. We
first propose models of Fe/Bi/MgO by considering lattice matching for the calculations
and then study the magnetism of Fe/Bi/MgO as well as Fe monolayer and Fe/MgO films.
It is found that enhancement in perpendicular magnetic anisotropy can be obtained byinserting the Bi layer at the Fe/MgO interface. The electronic origin of MCA in thesystems is discussed from the viewpoint of Bruno’s formula [1] and band structure within
the second-order purturbation theory [2].
[1] P. Bruno, Phys. Rev. B 39, 865 (1989).
[2] D. S. Wang, R. Wu, and A. J. Freeman, Phys. Rev. B 47, 14 932 (1993).

Poster-28

Tunable Thermoelectric Effects of Bilayer Graphene by
Vertical Electric Field
Hikaru Horii1, Kenji Sasaoka2, Takahiro Yamamoto1,2,* and Hidetoshi Fukuyama3
1Fac. of Engineering, Tokyo Univ. of Science, Katsushika, Tokyo 125-8585, Japan
2
WFS-T, RIST, Tokyo Univ. of Science, Katsushika, Tokyo 125-8585, Japan
3
Tokyo University of Science, Shinjuku, Tokyo 162-8601, Japan*

E-mail: takahiro@rs.tus.ac.jp

Thermoelectric (TE) generation is a potential key technology for recovering energy
from waste heat. Among the various potential candidates for TE materials, nanocarbon
materials have attracted attention as flexible and high-performance TE materials. Most
recently, Yamamoto and Fukuyama reported that the semiconducting carbon nanotubes(CNTs) exhibit high TE performance when the chemical potential μ locates near a bandedge with sharp density of states (DOS) originating from its one dimensionality [1,2]. On
the other hand, the graphene, which is a two-dimensional honeycomb lattice consistingof carbon atoms, cannot be expected to be high-TE performance because it has no band
gap at the charge neutral point.
In this study, we focus on the bilayer graphene (BLG) since the bandgap can be
opened by applying the electric field perpendicular to the BLG, as shown in Fig. 1 [3].
We have calculated the Seebeck coefficient S and the power factor PF of the BLG in thepresence of vertical electric field 𝑬 using the Kubo’s linear response theory combinedwith thermal Green’s function method which was recently developed [1,2]. We adopt theconstant-τ approximation for self-energy due to carrier scattering [2].
We found that the values of S and PF can be controlled by changing the magnitude of
𝑬 . For example, we obtained S ~ 200 μV/K and PF ~ 40 mW/mK2 when μ lies close toa band edge and the vertical electric field is 𝐸 = 4.8 MV/cm. This is because the DOS
of BLG under 𝑬 has a sharp peak near the bandedge, which is similar to carbon nanotubes. On theother hand, in the high-energy regimes where μ is
much larger than the band gap, S is inversely
proportional to the chemical potential, i.e., S ∝ μ-1.
The μ-1 behavior of BLG is similar to the case of
CNTs. In contrast to S, the thermoelectric
conductivity L12, which is defined as the electric
current density in response to the temperature
gradient, shows the different μ dependence
between the two-dimensional BLG and onedimensional CNTs.
[1] T. Yamamoto and H. Fukuyama, J. Phys. Soc. Jpn. 82, 024707 (2018).
[2] T. Yamamoto and H. Fukuyama, J. Phys. Soc. Jpn. (in press).
[3] T. Ohta et al. , Science 313, 951 (2006).

Poster-28

Poster-29

Noncollinear Spin Torque Effect in Magnetic
Heterojunctions: Combined First-Principles Calculation and
TB-NEGF Method
Bao-Huei Haung1, Chia-Chia Chao1, Yu-Hui Tang1,* and Chao-Cheng Kaun2
1

Department of Physics, National Central University, Jhong-Li, Taoyuan, Taiwan
Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan

2*E-mail: yhtang@cc.ncu.edu.tw

Our theoretical researches focus on searching for novel nm-scale
ferromagnetic/barrier/ferromagnetic (FM/B/FM) magnetic tunnel junctions (MTJs) withsuperior spin transport properties by choosing oxides [1] and organic molecules [2] as thecentral barriers. The relative orientation of two FM electrodes can be controlled by a spinpolarized current via the noncollinear spin torque effect. Recently, we have successfully
employed the single-band tight-binding (SBTB) model to predict the noncollinear spin
torque effect in FM/I/FM and FM/I/SF/I/FM [1] magnetic tunnel junctions, where I andSF represent insulting and spin-filter barriers, respectively. However, for real complex
heterojunctions, the injected spin-polarized electrons from FM electrode can be strongly
influenced by the complicated interfacial spin-polarized charge transfer, which is ignoredin our previous SBTB model.
In this study, our newly developed “JunPy” [3] package successfully combined theself-consistent Hamiltonian by using the first-principles calculation, including multi-band
dispersion relation and complicated interfacial coupling, with our newly derived TB
model and non-equilibrium Green’s function (NEGF) method to investigate thenoncollinear magnetotransport properties in nm-scale magnetic heterojunctions. This
program is first testified for the spin-polarized currents and the noncollinear spin torqueeffect in conventional Fe/MgO/Fe MTJ. We further employed it to predict the giant fieldlike spin torque (FLST) effect in the amine-ended single-molecule magnetic junction [5],which may open a new avenue for multifunctional manipulation in next-generation
organic FLST-MRAMs with lower power consumption. We believe that this newly
developed calculation process not only can efficiently resolve current self-consistentdifficulties in first-principles calculation for non-collinear case, but also may inspire
future experimental explorations in novel magnetic heterojunctions for future spintronics
applications. This work is supported by the Ministry of Science and Technology (MOST
106-2112-M-008-011- and 106-2633-M-008-002-) and the National Center for
Theoretical Sciences, Republic of China.
[1] Y. –H. Tang, et al. Phys. Rev. Lett. 103, 057206 (2009) and Sci. Rep. 5 11341 (2015).
[2] Y. –H. Tang, et al. J. Phys. Chem. C 120, 692 (2016).
[3] JunPy package https://labstt.phy.ncu.edu.tw/junpy[4] Nanodcal package http://nanoacademic.ca/showArticle.jsp?id=17[5] Y. –H. Tang and B. –H. Huang, J. Phys. Chem. C 122, 20500 (2018).

Poster-30

Polarization dependent optical response and layer-controlledband gap of group IV monochalcogenides
Jun Inagaki,1 Yu-Chung Pan,1 and Hung-Chung Hsueh1,2,*
1

Department of Physics, Tamkang University, Tamsui District, New Taipei
City,Taiwan, ROC
2
X-ray Science Research Center, College of Science, Tamkang University, Tamsui
District, New Taipei City,Taiwan, ROC*

E-mail: hchsueh@mail.tku.edu.tw

Sharing with the same bulk-like flake crystal structure of black phosphorus andphosphorene, group IV monochalcogenides exhibits unique many-electron effects in its
electronic and optical properties. Few-layer group IV monochalcogenides absorbs lightpolarized along the structures’ armchair direction and is transparent to light polarizedalong the zigzag direction, making them potentially viable linear polarized for
applications [1]. In this work, we employ first-principles excitation calculations based on
the combined GW+BSE approach to explore the electronic structure and optical responsewith respect to different polarizations of few-layer layered group IV monochalcogenides.
In addition to the strong polarization dependence of the optical absorption spectra, theband gap, excitation binding energies, and optical absorption spectrum of group IV
monochalcogenides can also be broadly tuned by changing the number of stacked layers.
This scenario serves as a convenient and efficient method for engineering the layeredmaterial’s excited-state properties.

[1] Hung-Chung Hsueh, Jia-Xuan Li, and Ching-Hwa Ho, Adv. Optical Mater. 6,
1701194 (2018).

Poster-31

Electronic transport simulation in nitrogen-doped carbon
nanotubes focusing on disappearance of Anderson
localization due to phonon scattering
Keisuke Ishizeki,1 Kenji Sasaoka,2 Kengo Takashima1 and Takahiro Yamamoto1,2*
1Department of Physics, National Central University, Jhong-Li, Taoyuan, Taiwan
Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan

2*E-mail: takahiro@rs.tus.ac.jp

Impurity-doped semiconducting carbon nanotubes (CNTs) are expected to be used asmaterials of next-generation field effect transistors or thermoelectric devices owing totheir remarkable electrical properties. As electrical resistance of a doped CNT arecharacterized mainly by impurity and phonon scatterings, previous theoretical studies
individually investigated their effects. When impurity concentration is high and theimpurity scattering dominates at low temperature, conduction electrons localize in CNT
and the resistance increases exponentially with tube length (non-ohmic transport). On theother hand, it is expected that, as temperature increases, the phonon scattering suppresses
such a localization phenomenon and the transport property becomes ohmic transport. In
order to know whether the localization occurs or not and estimate accurate the resistanceat a certain temperature and impurity concentration, both scatterings must be
simultaneously taken into account in electronic transport simulation.
In the present study, we investigated electronic transport properties in a nitrogen-doped(10,0)-CNT at finite temperatures using the Open-TDSE with MD simulation method
developed in a previous study [1], which can simultaneously treat both effects oflocalization phenomena due to impurity scattering and quantum decoherence due tophonon scattering. We confirmed that electrical resistance of a long CNT increases
exponentially with the tube length at 0 K (strong localization) while the resistanceincreases linearly at 300 K. This means that phonon scattering reduces phase coherenceof electrons. This work is the first theoretical report to investigate electronic transport ina nitrogen-doped CNT focusing on disappearance of localization phenomena due tophonon scattering.

[1] K. Ishizeki, K. Sasaoka, S. Konabe, S. Satofumi, and T. Yamamoto, Phys. Rev. B 96,
035428 (2017).

Poster-32

Microscopic understanding of magnetic interactions in bilayer
CrI3
Seung Woo Jang, Min Yong Jeong, Hongkee Yoon, Siheon Ryee,
and Myung Joon Han*
Department of Physics, Korea Advanced Institute of Science and Technology(KAIST), Daejeon 34141, Korea*

E-mail: mj.han@kaist.ac.kr

We performed the detailed microscopic analysis of the inter-layer magnetic couplings
for bilayer CrI3. As the first step toward understanding the recent experimental
observations and utilizing them for device applications, we estimated magnetic force
response as well as total energy. Various van der Waals functionals unequivocally point
to the ferromagnetic ground state for the low-temperature structured bilayer CrI3 which
is further confirmed independently by magnetic force response calculations. The
calculated orbital-dependent magnetic forces clearly show that eg-t2g interaction is the key
to stabilize this ferromagnetic order. By suppressing this ferromagnetic interaction andenhancing antiferromagnetic orbital channels of eg-eg and t2g-t2g, one can realize thedesirable antiferromagnetic order. We showed that high-temperature monoclinic stacking
can be the case. Our results provide unique information and insight to understand themagnetism of multi-layer CrI3 paving the way to utilize it for applications.

Poster-33

Type-I and Type-II nodal lines in a magnetic hexagonal InC
sheet
Sunam Jeon,1 Yun-Tak oh,2 and Youngkuk Kim2,*
1

Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419,
Korea
2
Department of Physics, Sungkyunkwan University (SKKU), Suwon 16419, Korea*

E-mail: youngkuk@skku.edu

Based on first-principles calculations, we design a novel two-dimensional magnetic
material exhibiting symmetry-protected nodal lines in momentum space. We first showthat indium carbide crystallizes in a single layered form of a hexagonal honeycomb lattice.
Then, we show that hexagonal InC energetically favors ferromagnetic ordering of spins.
An interesting feature unique to this magnetic two-dimensional material is the Fermi
surface geometry. We find that both type-I and type-II nodal lines occur near the Fermi
level in momentum space. While an alternating chain of electron and hole pockets appears
in the Fermi sufrace for both type-I and type-II cases, it is shown that the Fermi surfaces
exhibit characterisitc geometries distinctive between the type-I and type-II due todifferent signs of their band velocities. Our findings suggest that h-InC may provide a
new venue for 2D magnetism and the Fermi surface topology.

Poster-34

DFT+DMFT study of Pressure dependent Insulator-to-Metaltransition in molecular Jeff = 3/2 Mott insulator, GaTa4Se8
Min Yong Jeong,1 Jae-Hoon Sim,1 Ara Go,2 and Myung Joon Han1,*
1

2

Department of Physics, KAIST, Daejeon 34141, Korea
Center for Theoretical Physics of Complex Systems, IBS, Daejeon 34501, Korea*

E-mail: mj.han@kaist.ac.kr

The lacunar spinel compound GaTa4Se8 is known as the molecular Mott insulator,
exhibiting insulator-to-metal transition (IMT) and superconductivity at near 5GPa and
10GPa [1-3]. With first-principles density functional theory (DFT) study shows that spinorbit coupling (SOC) induce the Jeff = 3/2 ground state in 4d/5d series of lacunar spinelcompounds [4]. Recent resonant inelastic X-ray scattering (RIXS) experiments
established the spin-orbit entangled Jeff = 3/2 electronic structure [5]. In this study, we
performed DFT + DMFT calculations with exact diagonalization (ED) solver [6] tounderstand IMT under the pressure and role of the SOC. Using the realistic Hubbard U
parameter from constrained RPA [7], we found that the formation of the Jeff = 3/2 stateswith reasonable SOC is essential to reproduce IMT under the high pressure.
[1]
[2]
[3]
[4]
[5]
[6]
[7]

M.M. Abd-Elmeguid et al. PRL 93, 126403 (2004).
R. Pocha et al. PRL 110, 037401 (2013).
A. Camjayi et al. PRL 113, 086404 (2014).
H.-S. Kim et al. Nat. Commun. 5, 3988 (2014).
M. Y. Jeong et al. Nat. Commun. 8, 782 (2017).
A. Go, G. S. Jeon. J. Phys.: Condens. Matter 21, 48 (2009).
S. W. Jang et al. Sci. Rep. 6, 33397 (2016).

Poster-35

Topological Phase Transition in NaZnBixSb1−x
Jaemo Jeong1, Dongwook Kim1, and Youngkuk Kim1*
1

Department of Physics, Sungkyunkwan University (SKKU), Suwon 16419, Korea*

E-mail: youngkuk@skku.edu

Using first-principles calculations, we study the topological phase transition in
NaZnBixSb1−x that happens as the doping concentration x is varied. We show that NaZnBi
realizes Z2 topological insulator phase in a tetragonal ABC-type lattice, whileisostructural NaZnSb is a normal insulator. By employing virtual crystal approximation,
we also show that a topological phase transition occurs by substituting Bi with Sb via theappearance of Dirac semimetal phase at x = 0.45, which defines a topological criticalpoint. We elucidate the electronic structure responsible for the topological phasetransition. The evolution of topological surface states is studied as a function of thedoping concentration. Our results suggest that NaZnBixSb1−x should provide a new venue
for the study of topological phenomena.

Poster-36

Poster-37

Weyl and Triple Nodal Points in half-metallic ferrimagnets
Hyo-Sun Jin1 and Kwan-Woo Lee1,21Department of Applied Physics, Graduate School, Korea University, Sejong
2
Division of Display and Semiconductor Physics, Korea University, Sejong

For last decade years, many topological phases have been proposed and experimentallyobserved. Among them, recently, topological matters with various dimensional nodal
points have been gained a lot of interest. For example, Dirac and Weyl nodes are zerodimensional, nodal lines are one-dimensional, and nodal links are three-dimensional. In
particular, a novel 0D triple nodal point is of interest, since it has no high energy
counterpart.
In this presentation, we will address topological properties in the Cr-based inverse
Heusler compounds, showing magnetic Weyl points, triple nodal points, and nodal links
in the absence of spin-orbit coupling. Our surface state calculations, based on the Greenfunction approach, show several Fermi arcs connecting each Weyl point and each triple
nodal point. Furthermore, the triple nodal points are connected with the nodal links,
leading to the so called nexus fermionic state near the Fermi level. Using first principles
calculations, we will analyze the origin of these topological characters. Our results are
expected to provide a platform of a novel topological phase.

Acknowledgements: This research was supported by NRF Grants No. NRF2016R1A2B4009579.

Poster-38

Dominant in-plane cleavage direction of CrPS4 monolayer
Minwoong Joe,1,* and Changgu Lee1
1

School of Mechanical Engineering, Sungkyunkwan University, 2066 Seobu-ro,
Jangan-gu, Suwon 440-746, Republic of Korea*

E-mail: mjoe122@gmail.com

In-plane cleavage directions of 2D crystals are displayed and often well-defined in theirflakes exfoliated by the widely-used scotch-tape method. Here, we investigate thecorrelation between dominant in-plane cleavage direction and elastic properties indifferent directions. CrPS4 flakes show a preferential in-plane cleavage direction of 67.5˚,corresponding to <110> direction. To explain it, we calculated directional dependence ofYoung’s modulus and fracture energy using first-principles density functional theory
calculations. We found that fracture energy is directly relevant to the in-plane cleavage
direction of CrPS4. Our study can provide a facile approach to figure out the direction of
2D crystals without complex characterization process, which is valuable for material
processing of 2D materials.

[1] Joe, M, et al. J. Phys. Condens. Matter 29, 405801 (2017).

Poster-39

A Simple Method to Calculate the Exfoliation Energies ofLayered Materials
Jong Hyun Jung,1 Cheol-Hwan Park,1,* and Jisoon Ihm2
1

Department of Physics and Astronomy, Seoul National University, Seoul 08826,
South Korea
2
Department of Physics, Pohang University of Science and Technology, Pohang
37673, South Korea*

E-mail: cheolhwan@snu.ac.kr

The exfoliation energy, the energy required to peel off an atomic layer from the surface
of a bulk material, is of fundamental importance in the science and engineering of layeredmaterials. Traditionally, the exfoliation energy has been obtained from first-principles by
calculating the difference in the energy between (i) a slab of N layers (N1) and (ii) a
slab of N – 1 layers plus a layer separated from the slab. Here, we prove that the
exfoliation energy can be obtained exactly as the difference between the energy of a bulk
material (per atomic layer) and that of an isolated single layer [1]. The proposed method
is (i) tremendously lower in computational cost than the traditional approach because it
does not require calculations on thick slabs, and (ii) still valid even if there is a surface
reconstruction of any kind. Moreover, the method is (iii) capable of taking into accountthe relaxation of the exfoliated single layer, and (iv) easily combined with many-bodycomputational methods. As a proof of principles, we calculate the exfoliation energies ofgraphene, hexagonal boron nitride, MoS2, and phosphorene using density-functional
theory.
[1] J. H. Jung, C.-H. Park, and J. Ihm, Nano Lett. 18, 2759 (2018).

Poster-40

First-Principles Study of Alkali Metal Intercalated MoS2
Thanundon Kongnok and Sirichok Jungthawan*
1

School of Physics, and NANOTEC-SUT Center of Excellence on Advanced
Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima
30000, Thailand
2
Thailand Center of Excellence in Physics (ThEP), Commission on Higher
Education, Bangkok 10400, Thailand*

E-mail: sirichok@g.sut.ac.th

MoS2 is a compound in transition metal dichalcogenide (TMDC) family that is
semiconductor with layered honeycomb structure having strong in-plane bonding andweak out-of-plane van der Waals interactions. In the bulk form, MoS2 has an indirect
band gap, whereas monolayer form has direct band gap which is more suitable for device
applications. It has been proposed that the electronic characteristic of the monolayer canbe reproduced experimentally in MoS2 by K intercalation [1]. In this work, the effects ofdifferent alkali metal (such as Li, Na, K, and Rb) intercalation are investigated by using
first-principles calculations within the 2×2×1 supercell. In order to provide guidance formeasurement, the electronic structures from supercell calculations are unfolded onto thehigh symmetry paths [2] as defined in the first Brillouin zone of the primitive cell. The
results show significant expansion of interlayer spacing and contribution of electron
donation from alkali metal to the conduction band of MoS2. The expansion obviously
depends on atomic radii of the intercalated metals. Moreover, the conduction band
minimum is changed to the same location of the valence band maximum in k-spacebecause the expansion of the interlayer spacing reduces the electronic interactions
between adjacent layers creating a quasi-monolayer character. It has been found that theinterlayer spacing of MoS2K0.25 and MoS2Rb0.25 are large enough to exhibit quasimonolayer character. Furthermore, the effects of concentration of alkali metal have been
investigated by varying concentration of K within the given supercell. We found that inplane lattice constant increases proportional to the concentration. Our results suggest thatdifferent atomic radii and concentration of intercalated alkali metals could provide an
opportunity to tune electronic structures of TMDC materials.
[1] T. Eknapakul, P. D. C. King, M. Asakawa, P. Buaphet, R.-H. He, S.-K. Mo, H. Takagi,
K. M. Shen, F. Baumberger, T. Sasagawa, S. Jungthawan, and W. Meevasana, Nano Lett.
14, 1312–1316 (2014).
[2] M. Tomić, H. O. Jeschke, and R. Valentí, Phys. Rev. B 90, 195121 (2014).

Poster-41

Quantum Anomalous Hall Effect with Higher Chern
Numbers in Electron-Doped CrSiTe3: A First-Principles
Prediction
Sungmo Kang, Seungjin Kang, and Jaejun Yu*
Department of Physics and Astronomy, Center for Theoretical Physics, Seoul
National University, Seoul 08826, Korea*

E-mail: jyu@snu.ac.kr

The nontrivial topology of electronic band structure can give rise to many novel
phenomena like the quantum spin Hall effect (QSHE) or the quantum anomalous Hall
effect (QAHE). A Chern insulator is such a topological state of matter exhibiting anonzero quantized Hall conductivity without an external magnetic field. There have been
several experimental efforts to realize QAHE by doping magnetic impurities into
topological-insulator thin films. Here we report that the Chern insulator can be realized
in a single layer of electron-doped CrSiTe3. We have performed first-principles densityfunctional-theory calculations to find the minimum energy configuration for both atomic
and magnetic structures and determined that the ground state of pristine CrSiTe3 is aferromagnetic insulator. We use the Wannier function to calculate the Berry curvaturesand prove the nontrivial Chern numbers for the conduction bands consisting of mostly Cr
eg orbitals hybridized with neighboring Te p orbitals in the honeycomb-lattice network of
CrTe6 octahedrons. Further, we demonstrate that the electron-doping can raise the Fermi
level to the middle of the eg manifold, which opens up a band-gap of about 20 meV.
Consequently, the electron-doped CrSiTe3 becomes a QAHE insulator with higher Chern
numbers. The origin of higher Chern numbers is attributed to the presence of multiple
Dirac cones in the eg-manifold band structures without spin-orbit coupling, together withthe broken time-reversal symmetry of the ferromagnetic CrSiTe3. We confirm that the
nontrivial topology of the electron-doped CrSiTe3 remains robust in its bulk structure byshowing the chiral edge states by carrying out the edge state calculation. Our result
suggests that there is a new family of Chern insulator materials in the form of MAX2- or
MX3-type two-dimensional materials.
*Work supported by
2017R1A2B4007100).

the

National

Research

Foundation

of

Korea

[1] S. Kang, S. Kang, and J. Yu, J. Electron. Mater. (2018).
[2] N. Sivadas, M. W. Daniels, R. H. Swendsen, S. Okamoto, and D. Xiao, Phys.
Rev. B 91, 235425 (2015).
[3] Y. Sugita, T. Miyake, and Y. Motome, Phys. Rev. B 97, 035125 (2018).
[4] Q. Wu, S. Zhang, H.-F. Song, M. Troyer, and A. A. Soluyanov, Comput. Phys.
Commun. (2017).

(no.

Poster-42

Path Integral Molecular Dynamics Simulations for MuoniatedThioformaldehyde Radicals
Narissa Kanlayakan1, Yuki Oba2, Nawee Kungwan1,* and Masanori Tachikawa2,*
1

Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai,
Thailand2
Quantum Chemistry Division, Graduate School of NanoBioscience, Yokohama City
Uniersity, Yokohama, Japan*

E-mail: naweekung@gmail.com and tachi@yokohama-cu.ac.jp

A considerable amount of knowledge for muonium (Mu; complex of a positive muon (μ+)
atom and an electron) chemistry has been accumulated for over 30 years [1]. A muon has
a smaller mass and larger magnetic moment than those of proton. Because of these uniquefeatures, Mu atom is used as the muon spin resonance/
rotation/relaxation (µSR), where hyperfine coupling constant (HFCC) is a good index forthe magnetic interaction between electron and muon spins. In this study, we investigated
the structures and “reduced” HFCC values for muoniated and hydrogenatedthioformaldehyde radicals, a Mu or H atom is added to carbon atom (C-adduct) or sulfur
atom (S-adduct) of the thioformaldehyde compound (H2C=S) using the on-the-fly abinitio path integral molecular dynamics (PIMD) method [2, 3], which can include both
nuclear quantum and thermal effects. The single point energy of C adduct structure with
CCSD/aug-cc-pVDZ (optimized with MP2/6-311++G(d,p)) level is 13.48 lower than thatof S-adduct structure, corresponding the previous study [4]. The HFCC values from a
simple geometry optimization calculation of C adduct and S adduct are 22.42 and -7.39
MHz, respectively, at the BHandHLYP/6-31+G(d,p) level. In case of C-adduct, thereduce HFCC values of the muoniated thioformaldehyde radical by our PIMD simulationis slightly larger than that of hydrogenated radical with the same calculation level. We
found that the local molecular structures affect the HFCC values, particularly, the Mu⸺C
bondlength in the muoniated thioformaldehyde radical is lengthen due to the large nuclear
quantum effect of moun.

Figure 1. The optimized structure of muoniated and hydrogenated thioformaldehyde radicals (MuThio and H-Thio).
[1]
[2]
[3]
[4]

P. W. Percival, Radiochemica Acta 26, 1 (1979).
K. Yamada, Y. Kawashima, and M. Tachikawa, J. Chem. Theory Comput. 10, 2005 (2014).
Y. Oba, T. Kawatsu, and M. Tachikawa, J. Chem. Phys. 145, 064301 (2016).
T. Kobayashi, K. Seki, T. Tanaka, and T. Takayanagi, Comput. Theor. Chem. 963, 2-3 (2011).

Poster-43

Benchmark of density functional theory for superconductors
in elemental materials
Mitsuaki Kawamura,1,* Taisuke Ozaki1
1Institute for Solid State Physics, The University of Tokyo, Kashiwa, Japan*

E-mail: mkawamura@isp.u-tokyo.ac.jp

The first-principle calculation of the superconducting properties such as the transition
temperature and the gap function is of great interest to explore new materials as well as
to understand the mechanism of known superconductor. Density functional theory forsuperconductors (SCDFT) [1] is one of the framework for such calculations; this method
enables us to perform fully non-empirical simulation in the superconducting phase withinreasonable computational cost. In this method, we can treat the electron-phonon
interaction, the electron-electron repulsion, and the spin-fluctuation mediated interaction[2] in the first-principles manner. However, the accuracy of the current approximatedfunctional of SCDFT and the effects of the spin-orbit interaction (SOI), spin-fluctuation,and the phononic anharmonicity has not been verified systematically although such averification is highly desirable before we apply this method to the wide range of materials.
Such a benchmark is also useful to find the guideline for improving the superconducting
density functional. For this purpose, we started the benchmark calculation of SCDFT with
our newly developed first-principles program package Superconducting-Toolkit (SCTK)[3]. In this presentation, we show benchmark results of superconducting properties
calculated by SCDFT for 32 elemental materials together with computational details, anddiscuss accuracy of predicted transition temperature TC and the effect of the spin-orbit
interaction up on TC (see Fig. 1).

Figure 2: (color online) Superconducting gap of Pb computed by taking account of the spin-orbit
interaction. If we ignore this interaction, the maximum- and the minimum- value of the gap
function are reduced to 0.89 meV and 0.63 meV, respectively.

[1]M. Lüders, et al. Phys. Rev. B 72, 024545 (2005).
[2] F. Essenberger, et al. Phys. Rev. B 90, 214504 (2014).
[3] M. Kawamura, R. Akashi, and S. Tsuneyuki., Phys. Rev. B 95, 054506 (2017).
http://sctk.osdn.jp/index.html

Poster-44

Semimetallicity and Negative Differential Resistance from
Hybrid Halide Perovskite Nanowires
Muhammad Ejaz Khan, Juho Lee, Seongjae Byeon, and Yong-Hoon Kim*
School of Electrical Engineering and Graduate School of Energy, Environment, Water,and Sustainability, Korea Advanced Institute of Science and Technology, 291 Daehakro, Yuseong-gu, Daejeon 34141, Korea*

Corresponding author. E-mail: y.h.kim@kaist.ac.kr

In the rapidly progressing research on organometal halide perovskites, the dimensional
reduction could open up new venues to improve material properties and introduce
additional functionalities. Herein, carrying out first-principles calculations, we consider
the nanostructuring and device applications of the recently synthesized
trimethylsulfonium lead triiodide (CH3)3SPbI3 perovskite. We find that the onedimensional (1D) (CH3)3SPbI3 structure is energetically and dynamically stable, and theelectronic structures of higher-dimensional forms are robustly determined at the 1D level.
Upon removing organic ligands, the 1D PbI3 column consisting of face-sharing [PbI6]
octahedra is also found to be structurally stable and, more interestingly, have a semimetallic character, contradicting the conventional assumption of semiconducting metalhalogen inorganic frameworks. Adopting the bundled nanowire junctions consisting ofsemiconducting (CH3)3SPbI3 channels sandwiched between semi-metallic PbI3
electrodes, we finally obtain a high negative differential resistance (NDR) characteristics.
We show that the NDR results from a novel mechanism that involves the quantummechanical delocalization of channel electronic states and its disruption with increasing
bias voltages. Our work demonstrates the great potential of low-dimensional hybrid
perovskites toward advanced electronic devices beyond actively-pursued photonic
applications.

Poster-45

Non-Covalent Interactions in Density Functional Calculations
Yeil Kim, Suhwan Song, and Eunji Sim*
Department of Chemistry, Yonsei University, 50 Yonsei-ro Seodaemun-gu, Seoul,
Korea*

E-mail: esim@yonsei.ac.kr

In this presentation, we introduce a practical method to correct various non-covalentinteractions in density functional theory (DFT) using density-corrected DFT (DCDFT)[1-2] and dispersion-corrected DFT (DFT-D). Various non-covalent interactions are
considered an important role in the structure of materials and supramolecules. Despite
DFT’s good balance between accuracy and computational cost, there still remain somechallenges in DFT. To solve one of these problems, S.Grimme’s group developed the
DFT-D3 method[3], an efficient silico-empirical method for non-covalent interactions
with a predominance of dispersion. This correction can achieve better results in π-πinteractions, hydrogen bonds, and some dispersion-dominant interactions using somestandard benchmark sets. However, in the case of halogen bond, similar to hydrogenbonding in the aspect of dipole-dipole interaction, the result of DFT is worsened whendispersion correction is added. To classify the error in DFT, we employed the error
classification of functional and density-driven errors. As a result, unlike other interactions,
we found that halogen-bond is much more sensitive to density, which means density
correction is necessary to cure the DFT error. By examining the B30 and the S22 datasets,
we show that HF-DFT-D corrects the density and the dispersion simultaneously. The HFDFT-D method provides more accurate results for non-covalent interactions, whether
errors in standard DFT calculations are due to static or van der Waals forces.
[1] M.-C. Kim, E. Sim, and K. Burke, Phys. Rev. Lett., 111, 073003 (2013).
[2] A. Wasserman, J. Nafziger, K. Jiang, M.-C. Kim, E. Sim, and K. Burke, Ann. Rev.
Phys. Chem., 68, 555-581 (2017).
[3] S. Grimme, J. Antony, S. Ehrlich, and H. Krieg J. Chem. Phys. 132, 154104 (2010).

Poster-46

Odd-even phonon transport effects in strained carbon atomic
chains bridging graphene nanoribbon electrodes
Hu Sung Kim,1 Tae Hyung Kim,1 and Yong-Hoon Kim1,*
1

Department of Physics, Korea Advanced Institute of Science and Technology(KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea*

E-mail: y.h.kim@kaist.ac.kr

Based on first-principles approaches, we study the ballistic phonon transportcharacteristics of finite monatomic carbon chains stretched between graphene
nanoribbons, an sp1-sp2 hybrid carbon nanostructure that has recently seen significant
experimental advances in its synthesis. We find that the lattice thermal conductanceanomalously increases with tensile strain for the even-numbered carbon chains that adopt
the alternating bond-length polyyne configuration. On the other hand, in the oddnumbered carbon chain cases, which assume the equal bondlength cumulene
configuration, phonon conductance decreases with increasing strain. We show that thestrong odd-even phonon transport effects originate from the characteristic longitudinal
acoustic phonon modes of carbon wires and their unique strain-induced redshifts withrespect to graphene nanoribbon phonon modes. The novel phonon transport properties
and their atomistic mechanisms revealed in this work will provide valuable guidelines indesigning hybrid carbon nanostructures for next-generation device applications such as
nanobiosensors.
[1] H. S. Kim, T. H. Kim, and Y.-H. Kim, Carbon. 142, 107 (2019).

Poster-47

Abnormalities in Density Functional Calculations
on Ions and Radicals and its solution:
Density-Corrected Density Functional Theory
Min-Cheol Kim,1 Kieron Burke,2 and Eunji Sim3,*
1

Computational Science Research Center, Korea Institute of Science andTechnology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul, Korea
2
School of Physical Sciences, University of California, Irvine, CA 92697,USA
3
Department of Chemistry, Yonsei University, 50 Yonsei-ro Seodaemun-gu, Seoul,
Korea*

E-mail: esim@yonsei.ac.kr

In this presentation, we introduce a systematic and practical way to correct various
abnormalities in density functional theory(DFT) using density-corrected DFT (DCDFT)[1-5]. DFT is a widely used electronic structure calculation method due to its goodbalance between accuracy and computational cost. One of the challenges in DFT iscalculating equilibrium structures, electronic structures, and potential energy surfaces ofanions and radicals, where it suffers greatly from the self-interaction error. This includes
unphysical positive HOMO energies for anions, predicting incorrect ground stategeometry for radical complexes, incorrect dissociative behavior for molecular species.
Here, we perform a very simple analysis on the source of error of DFT calculations andclassify DFT calculations into two different groups: normal and abnormal calculation.
We show that one can easily determine an abnormal calculation, and “cure” it using DCDFT. We apply DC-DFT on problematic cases especially for ions and radicals andshow it gives excellent results.
[1] M.-C. Kim, E. Sim, and K. Burke, J. Chem. Phys. 134(17), 171103 (2011).
[2] M.-C. Kim, E. Sim, and K. Burke, Phys. Rev. Lett., 111, 073003 (2013).
[3] M.-C. Kim, E. Sim, and K. Burke J. Chem. Phys. 140, 18A528 (2014).
[4] M.-C. Kim, H. Park, S. Son, E. Sim, and K. Burke, J. Phys. Chem. Lett. 6, 3802-3807(2015).
[5] A. Wasserman, J. Nafziger, K. Jiang, M.-C. Kim, E. Sim, and K. Burke, Ann. Rev.
Phys. Chem., 68, 555-581 (2017).

Poster-48

First-principles-based calculation of branching ratio for 5d,
4d, and 3d transition metal systems
Do Hoon Kim1, Jae-Hoon Sim1, Hongkee Yoon, and Myung Joon Han1,*
1

Department of Physics, Korea Advanced Institute of Science and Technology(KAIST), Daehak-ro 291, Korea*

E-mail: mj.han@kaist.ac.kr

A first-principles computation scheme to calculate ‘branching ratio’ in x-ray absorption
spectroscopy has been applied to various 5d, 4d, and 3d transition-metal elements andcompounds. This new method is based on an atomic theory which assumes the atomic
core hole interacts barely with valence electrons [1, 2]. While it provides an efficient way
to calculate the experimentally measurable quantity without generating spectrum itself,
its reliability and applicability should be carefully examined especially for the lighttransition metal systems. Here we select 30 different materials and compare thecalculation results with experimental data. It is found that our scheme well describes 5d
and 4d transition metal systems whereas, for 3d materials, the difference between thecalculation and experiment is observed. The difference for 3d transition metal system is
attributed to the neglect of core-valence interaction. We expect that our results shed lighton the applicability of the method.
[1] J.-H. Sim, H. Yoon, S. H. Park, and M. J. Han, Physical Review B 94, 115149 (2016).
[2] B. T. Thole and G. van der Laan, Physical Review A 38, 1943 (1988).

Poster-49

Comparing two mapping formalisms for mixed quantumclassical simulations of complex systems
Hyun Woo Kim*
Center for Molecular Modeling and Simulation,
Korea Research Institute of Chemical Technology (KRICT),141 Gajeongro, Yuseong, Daejeon 34114, Korea*

E-mail: ahwk@krict.re.kr

Molecular dynamics simulations on multiple electronic states are important inunderstanding photochemical processes in complex systems. One of widely studied
examples is the excited-state proton transfer in solvated pigment molecules. In thisexample, there are many degrees of freedom in pigment and solvent molecules which are
intractable for full quantum mechanical descriptions. Instead, by combining quantum
mechanical and classical mechanical treatments, one can carry out quantum dynamics
simulations for important degrees of freedom and classical simulations for remaining
ones. These hybrid methods are called as mixed quantum-classical (MQC) approaches.
Several MQC algorithms were developed under mapping formalisms, which relate thedynamics in many electronic states to that of fictitious harmonic oscillators. Thesealgorithms can be applied to all-atom molecular dynamics simulations of electronically
excited systems. However, there is still a constant need for improving existing algorithms
suitable for describing more complex systems in more efficient manner. To this end, I
will present the analyses of two MQC approaches based on mapping formalisms, Poissonbracket mapping equation (PBME) and forward-backward trajectory solution (FBTS) of
quantum-classical Liouville equation (QCLE). First of all, I will focus on the error of
approximate PBME and FBTS of QCLE which should be accumulated in the long-time
simulations. With our simulation results for two-state models, I will discuss how
approximations made in deriving these approaches affect the population dynamics.

Poster-50

Poster-51

Atomistic origins of low-resistance metal contacts to phaseengineered MoS2
Tae Hyung Kim1, and Yong-Hoon Kim1,*
1

School of Electrical Engineering, Korea Advanced Institute of Science andTechnology (KAIST), 291 Daehak-ro, Daejeon, 34141, Korea*

E-mail: y.h.kim@kaist.ac.kr

In realizing high-performance electronic devices based on transition metal
dichalcogenides (TMDCs), the high contact resistance of the metal-TMDC interface
remains a major obstacle to overcome. Recently, the phase engineering of TMDCs in themetal contact region has been demonstrated as a promising scheme to achieve lowresistance contacts for TMDC transistors, but its atomistic mechanisms remain unclear.
Here, carrying out density functional theory (DFT) and DFT-based matrix Green’s
function calculations, we systematically explore the roles of 1T MoS2|2H MoS2 andmetal/1T MoS2 interfaces in lowering contract resistance for the phase-engineered
TMDCs by considering different electrode metal species (In, Pd, Au) and the top andedge contact configurations. We will clarify the cooperative effects between the extrinsic
metal|1T MoS2 interface and the intrinsic 1T MoS2|2H MoS2 counterpart in improving
the charge injection from the metal electrode into the 2H MoS2 channel.

Poster-52

Z2 monopole nodal lines in ABC graphdiyne
Junyeong Ahn1, Donwook Kim2, Youngkuk Kim2,*, Bohm-Jung Yang1
1

2

Department of Physics, Seoul National University, Seoul 08826, Korea
Department of Physics, Sungkyunkwan University (SKKU), Suwon 16419, Korea*

E-mail: youngkuk@skku.edu

A topological nodal line semimetal refers to a topological state of matter characterized byprotected one-diemsional gapless excitations in momentum space. While a Z2 Berryphase nodal line semiemtal is one of the most widely studied topological nodal line
semimetals with many material realizations, there is yet another class of nodal line
semimetal, referred to as Z2 monopole nodal line semimetals, which has remained widely
unexplored without a suggested material realization yet. Using first-principles
calculations, we show that a three-dimensional carbon allotrope, ABC graphdiyene,
realizes the Z2 monopole nodal line semimetal [1]. We calculate a Z2 Stiefel-Whitney
number and a linking number that dictate the Z2 monopole nodal line semimetal phase in
ABC graphdiyene. We also show that ABC graphdiyne hosts two-dimensional StiefelWhitney insulating phase in two-dimensional subsystems of the Brillouin zone, which
can be considered as a fragile topological insulator phase. Our findings suggest that ABC
graphdiyene should serve as a new venue for the study of topological semimetals.
[1]

Ahn, J., Kim, D., Kim, Y., & Yang, B. J., Phys. Rev. Lett. 121, 106403 (2018).

Poster-53

Ab Initio Calculations of Electrical Structures of Water
Adsorbed on Graphene
Yusei Kioka,1 Yuki Maekawa,2Kenji Sasaoka,3 Takahiro Yamamoto1,2,3,*

1

Department of Electrical Engineering, Tokyo University of Science, Tokyo, 1258585, Japan2
Department of Liberal Arts, Tokyo University of Science, Tokyo, 125-8585, Japan
3
Water Frontier Science & Technology Research Center, RIST, Tokyo University of
Science, Japan*

E-mail: takahiro@rs.tus.ac.jp

A graphene, which consists of carbon atoms arranged in hexagonal lattice, is well
suited for exploring an interaction between a material surface and a molecule. This isbecause it is an atomically flat and non-polar material. It had long been considered thatgraphene cannot be adsorbed by water molecules because it is a hydrophobic material.
However, the previous molecular dynamics (MD) simulations confirmed that there are
single or double water layers on a graphene surface, depending on the number of watermolecules [1,2]. Similar layer structures have already been reported for a carbon nanotube
by Homma et.al., and they found such layer structures formed around the carbon nanotube
by both photoluminescence measurements and classical MD simulations [3]. Although
the layer structure perpendicular to a graphene surface has been rigorously researched,
the microscopic structure parallel to the surface has not yet been fully characterized,
meaning that the hydrogen bonding network in the water layers on graphene is notunderstood enough. Moreover, the influence of surface water on the electronic states of agraphene remains to be elucidated yet although this is essential for developing ofgraphene-based devices, such as a graphene field-effect transistor.
In this work, we constructed microscopic structures of surface water adsorbed on afree-standing graphene and a graphene attached on a hexagonal boron nitride substrateusing classical molecular dynamics simulations. For the obtained structures, weinvestigated the influence of surface water on electronic states of a graphene using ab
initio calculations based on the density functional theory. From the above methods, weclarified that the characteristic polygonal structures appear in the two-dimensionalhydrogen-bond network [4]. We present that the structure of surface water and theelectronic states of water adsorbed on a graphene.
[1] T. A. Ho and A. Striolo, J. Chem. Phys. 138, 054117 (2013).
[2] A. Akaishi, T. Yonemaru, and J. Nakamura, ACS Omega 2, 2184 (2017).
[3] Y. Homma, et al. Phys. Rev. Lett. 110, 157402 (2013).
[4] Y. Maekawa, K. Sasaoka and T. Yamamoto, Jpn. J. Appl. Phys. 57, 035102 (2018).

Poster-54

First-Principles Electronic Transport Propertiesof Ge/amorphous Al2O3/Au Structure
Eunjung Ko1, Jaehong Park1,2, and Jung-Hae Choi1,*
1Center for Electronic Materials, Korea Institute of Science and Technology, Seoul
02792, Korea
2
Department of Materials Science and Engineering, Seoul National University, Seoul
08826, Korea*

E-mail: choijh@kist.re.kr

The Ge-based metal-oxide-semiconductor devices have Ge/high-k dielectric oxide/metal
gate structures. Although many experimental studies on the gate leakage current of thesestructures have been performed in terms of the scaling down issues, first-principles
theoretical works on the tunneling current density and, even, electronic structures havebeen rarely reported. Therefore, we investigate the first-principles electronic structures
and the tunneling effect through the potential barrier of high-k oxide. The Ge/a-Al2O3/Au
structure was chosen as a model system and three different nanometer scale thicknessesof a-Al2O3 are considered. The electronic transport properties of the Ge/a-Al2O3/Au
structure are compared with those of the Ge/a-Al2O3/Ge structure. The tunneling effectunder a positive and negative bias in Ge/a-Al2O3/Au structures is also presented thus thecurrent vs. bias voltage characteristic curve is shown.

Poster-55

DFT-based engineering of Dirac surface states in topologicalinsulator multilayers
Takao Kosaka,* Kunihiko Yamauchi, and Tamio Oguchi
Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka,
Ibaraki, Osaka 567-0047, Japan*

E-mail: t.kosaka@cmp.sanken.osaka-u.ac.jp

Topological insulators exhibit the non-trivial quantum states which can be characterized
by the insulating bulk states and spin-polarized metallic surface states, such as surface
states with Dirac cone, being expected for spintronics device applications. The highly
insulating bulk state and the tunable Dirac cone are required for the future device
applications. Nevertheless, many of topological insulators have been found to be metallic
due to the existence of impurities and disorder. It has been reported that the ternary
tetradymite topological insulator materials such as Bi2Te2Se [1], which forms the ordered
Te-Bi-Se-Bi-Te quintuple layers, and Bi2-xSbxTe3-ySey solid solution [2,3] have highlybulk insulating states, because the defect formation is suppressed in these materials. In
additoin to such defect control, one can obtain spin-polarized Dirac carries with the Diracpoint in the band gap. In thisstudy, we control the Diracsurface states by engineering
topological multilayer structures
using
first-principles
calculations based on density
functional
theory.
The
computational results show thatthe Dirac point can be modulated
in energy by differentiating work
functions between the surface
layers and the inner layers to Fig. 1: Band sturcture of topologicalrealize the desired band strcuture
insulator multilayers: bulk band in black andas shown in Fig. 1.
[1] Z. Ren, A. A. Taskin, S. Sasaki, K. Segawa, and Y. Ando, Phys. Rev. B 85, 155301(2012).
[2] Z. Ren, A. A. Taskin, S. Sasaki, K. Segawa, and Y. Ando, Phys. Rev. B 82, 241306(R)(2010).
[3] T. Arakane, T. Sato, S. Souma, K. Kosaka, K. Nakayama, M. Komatsu, T. Takahashi,
Z. Ren, K. Segawa, and Y. Ando, Nat. Commun. 3, 636 (2012).

Poster-56

Can exact KS potential reproduce HOMO-LUMO gap?:
analytically solvable two-electron system
Taichi Kosugi1* Yu-ichiro Matsushita2
1

Department of physics, The University of Tokyo,
7-3-1 Hongo Bunkyo-ku Tokyo, Japan
2
Laboratory for Materials and Structures, Tokyo Institute of Technology,
R3-7, 4259 Nagatsuta Midori-ku Yokohama, Japan*

E-mail: kosugi.taichi@gmail.com

Clear understanding of one-particle Green’s function (GFs) for interacting electronicsystems is important for material science since photoemission spectra are the GFs undersome assumptions[1-3]. To capture the essential physics encoded in GFs, we study the
one-particle GF of an interacting two-electron model system confined to a harmonic
potential[4]. Since the calculation of GF requires the energy eigenstates of thecorresponding three-electron system, we solve the Schroedinger equation analytically toobtain the exact solutions, from which we construct explicitly the simultaneous
eigenstates of the energy and total spin for the first time. The solutions for the threeelectron system allow us to derive analytic expressions for the exact one-particle GF forthe two-electron system. We calculate the GF in frequency domain to examine
systematically its behavior depending on the electronic interactions. We also compare thepole structure of non-interacting GF using the exact Kohn-Sham (KS) potential with thatof the exact GF to find that the discrepancy of the energy gap between the KS system andthe original system is larger for a stronger interaction. We perform numerical examinationon the behavior of GFs in real space to demonstrate that the exact and KS GFs can haveshapes quite different from each other. Our simple model will help to understand genericcharacteristics of interacting GFs.
[1] A. Damascelli, Phys. Scr. 2004, 61 (2004).
[2] S. Moser, J. Electron Spectrosc. Relat. Phenom. 214, 29 (2017).
[3] T. Kosugi, H. Nishi, Y. Kato, and Y.-i. Matsushita, J. Phys. Soc. Japan 86, 124717(2017).
[4] T. Kosugi and Y.-i. Matsushita, to be published in J. Phys.: Condens. MatterPoster-57

Electronic transport through the Ni/ZrO2 interface: Firstprinciples calculations
Kuan-Bo Lin1, 2, Yun-I Ho1, 2, Yen-Hsun Su1, * and Chao-Cheng Kaun2, *1 Department of Materials Science and Engineering, National Cheng Kung University,
Tainan, Taiwan
2 Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan*

E-mail: kauncc@gate.sinica.edu.tw
E-mail: yhsu@mail.ncku.edu.tw

Solid oxide fuel cells (SOFC) have advantages of higher energy density, higher
conversion efficiency and non-pollution than other types of fuel cells. Although Ni/ZrO2
is a conventional anode material of them and influences their conversion efficiency, theeffect of interface orientations on junction conductance has been rarely addressed. In thiswork, we study the geometric and electronic properties of the Ni/ZrO2 heterostructuresfrom first-principle, based on density functional theory and non-equilibrium Green's
function formalism, focusing on the effect of six interface orientations on conduction
features. Whereas hydrogen and methane are the common fuels in the usage of SOFC andtheir open circuit voltages are respectively 1.05 V and 1.15 V, our results suggest that
SOFC with the 90o heterostructure would offer better performance among the studiedorientations.

Poster-58

Topological Stability of Two-Dimensional Penta-Structures: acase of PdSe2
Artem Kuklin, Pavel Avramov*
Department of Chemistry, College of Natural Sciences, Kyungpook National
University, 80 Daehakro, Bukgu, Daegu, 41556, South Korea*

E-mail: paul.avramov@gmail.com

Here, we report a new approach to analize stability and apply them to several
recently proposed penta-structures including experimentally observed penta-PdSe2
monolayer. Despite the fact that various 2D penta- structures have been predicted before,
PdSe2 is the only one observed experimentally. It is found that stabilization of 2D PdSe2
is resulted from lowering of the symmetry during bulk-monolayer transition andstructural-induced force compensation. The absence of internal flexural stresses in the
single layer PdSe2 is validated by finite cluster approach as well as calculations ofdifferent diameter and chirality nanotubes. Electronic properties of (n,0) nanotubes reveal
the direct dependence of indirect bandgap width on dimeter of the nanotube while (n,n)
tubes with a diameter of (12,12) and higher possess transition to the direct bandsemiconductor that can be suitable for optoelectronic applications. Applying the same
metods to other recently-proposed penta-structures, large instability was found in pentagraphene, penta-SiC2, penta-AlN2, penta-B2C, penta-CN2, petna-SnS2 and so on, that
demonstrate the power of these methods.

Poster-59

Electron-Phonon Coupling, Superconductivity andnontrivial Band Topology in NbN Polytypes
Kunchala Ramesh Babu and Guang Yu Guo
Department of Physics and Center for Theoretical Physics, National Taiwan
University, Taipei 10617, Taiwan
Physics Division, National Center for Theoretical Sciences, Hsinchu 30013, Taiwan* E-mail: gyguo@phys.ntu.edu.tw
Materials that show both topological properties and superconductivity received
considerable interest because of the realization of Majorana Fermions i.e., particles with
their own anti-particles in such condensed matter systems [1]. Therefore, it is highly
demanding to investigate for the materials that has topological properties andsuperconductivity. Niobium Nitride, NbN, a well-known transition metal nitride is a goodsuperconducting material in its cubic structure (-NbN) with transition temperature Tc of
17.3 K [2]. Recent experiments on hexagonal NbN (-NbN) reveal the existence ofsuperconductivity with a Tc of 11.6 K [3]. On the other hand tungsten carbide (WC) type
NbN possesses topological properties with band crossing that has three fold degeneracy
along a particular k-vector path in the Brillouin zone [4]. Therefore, NbN is a goodcandidate that show topological properties as well as superconductivity.
Here we study the electronic structure, lattice dynamics and electron-phonon interactionsin -NbN, -NbN and WC-NbN by performing ab initio density functional calculations.
The calculated electronic band structures indicate that the Nb d-states are dominant near
Fermi level (EF). Interestingly, they also reveal that all three NbN polytypes are
topological metals. Specifically, -NbN and  -NbN are, respectively, type-II and type-I
Dirac metals, while WC-NbN is an emergent topological metal with exotic triply
degenerate nodes. The calculated phonon dispersion relations of -NbN are in good
agreement with neutron scatterring experiments. The phonon density of states andEliashberg functions show that the electron-phonon coupling in -NbN ( = 0.98) is muchstronger than in -NbN (= 0.16) and WC-NbN ( = 0.11). This results in a much higher
superconducting transition temperature (Tc = 18 K) than in -NbN and WC-NbN (Tc 1.0 K). Our findings thus suggest that the three NbN polytypes would provide valuable
opportunities for studying exotic phenomena arising from the interplay between
superconductivity and band topology.
[1]. G. Bian, T. R. Chang, A. Huang, Y. Li, H. T. Jeng, D. J. Singh, R. J. Cava, and W.
Xie, Phys. Rev. Mat. 1, 021201 (R) (2017).
[2]. M. W. Williams, K. M. Ralls, and M. R. Pickus, J. Phys. Chem. Solids 28, 333(1967).
[3]. Y. Zou, X. Qi, Cheng Zhang, S. Ma, W. Zhang, Y. Li, T. Chen, X. Wang, Z. Chen,
D. Welch, P. Zhu, B. Liu, Q. Li, T. Cui, and B. Li, Sci. Rep. 6, 22330 (2016).
[4]. G. Chang, S. Y. Xu, S. M. Huang, D. S. Sanchez, C. H. Hsu, G. Bian, Z. M. Yu, I.
Belopolski, N. Alidoust, H. Zheng, T. R. Chang, H. T. Jeng, S. A. Yang, T. Neupert,
H. Lin, and M. Zahid Hasan, Sci. Rep. 7, 1688 (2017).
[5]. G. Kresse, J. Hafner, Phys. Rev. B 47, 558 (1993).

Poster-60

Carrier doping effect on all-Heusler giant-magnetoresistancejunctions with semimetallic Fe2VAlstudied by first-principles calculations
Fumiaki Kuroda,1,2* Tetsuya Fukushima, 1,2,3 and Tamio Oguchi1,2,3
1

Institute of Scientific and Industrial Research, Osaka University, Japan
2
Center for Spintronics Research Network, Osaka University, Japan
3
Institute for Datability Science, Osaka University, Japan*

E-mail: fkuroda@cmp.sanken.osaka-u.ac.jp

For read sensors of ultrahigh-density hard disk drives (HDD) and Gbit-class spin transfer
torque magnetoresistive random access memories (STT-MRAMs), magnetoresistive(MR) devices satisfying high MR ratio and small resistance–area (RA) have been required.
Current-perpendicular-to-plane giant magnetoresistive (CPP-GMR) junctions are
expected to be one of the good candidates that have much smaller RA than tunnelingmagnetoresistive junctions. However, small RA values are not suitable for read sensors,
because high voltage output can not be obtained. Therefore, new junctions with asemiconducting spacer has drawn much attention [1,2]. In this work, we investigate
interfacial magnetic couplings and spin-dependent transport property in all-Heusler based
CPP-GMR junctions with a semimetallic Fe2VAl spacer on the basis of first-principles
calculations. A half-metallic ferrimagnet Mn2VAl is used for a spin injector and is thought
to be highly promising for spintronics devices at room temperature because the expectedcurrent to flip the spin would be rather low. The Korringha-Kohn-Rostoker (KKR)
Green’s function method with the AkaiKKR code is utilized to compute the magnetic
coupling constants between the magnetic atoms. For calculating the ballistic conductance,
we use the PWCOND code which is part of Quantum-Espresso package. It is found fromour calculations that, in MnMn-VAl termination, the interfacial Mn atoms are
antiferromagnetically coupled with V atoms of Fe2VAl. In addition, half-metallic states
are also preserved in the interfacial reigion. The transport property is governed by anelectron pocket in the band structure, originating from the V d states. Electron-carrier
doping in Fe2VAl enhances the conductivity, while hole-carrier doping hardly affects it.
This carrier doping effect from band matching leads to a new function in CPP-GMR
junctions. When carriers are introduced in the spacer by a gate voltage, magnetoresistancemight be changed significantly. Moreover, from comparison with spin injectors withother half-metallic Heusler alloys, controlling mechanisms in this type of CPP-GMR
junctions is discussed.
[1] S. Kasai, Y. K. Takahashi, P.-H. Cheng, Ikhtiar, T. Ohkubo, K. Kondou, Y. Otani, S.
Mitani, and K. Hono, Appl. Phys. Lett. 109, 032409 (2016).
[2] K. Masuda, and Y. Miura, Jpn. J. Appl. Phys. 56, 020306 (2017).

Poster-61

First-principles Study of Band Gap Tunability in
Hydrogenated Graphene
Viet-Duc Le,1 Eui-Sup Lee,1 and Yong-Hyun Kim1,2,*
1

Gradudate School of Nanoscience and Technology, KAIST, Daejeon 34141,
Republic of Korea
2
Department of Physics KAIST, Daejeon 34141, Republic of Korea*

E-mail: yong.hyun.kim@kaist.ac.kr

There have been on-going efforts to tune the electronic structure of graphene throughchemical modifications. Notable examples include graphane, a two dimensional
analogue of diamond, obtained through complete hydrogenation of graphene. The
hydrogen coverage undoubtly presents a experimentally accessible way to open the band
gap of graphene. In this study, we present a systematic approach to instill hydrocarbon
motifs in single-side hydrogenated graphene (SSHG) presumably in contact with
substrate. Here, we employed electron counting rules, a well-established formalism fordangling bonds at semiconductor surfaces, in combination with first-principles
calculations to identify the most probably SSHG structures and their corresponding
electronic properties. Here, the bandgap opening can be atributed to quantum
confinement of isolated aromatic hydrocarbon motifs based on benzene embedded ingraphene through hydrogenation. In contrast, conducting polymer motif based onpolyacetylene gives rise to robust metallic properties against Peierls distortion. Our
results suggest an efficient way to prepare graphene-based devices with suitable band gap
through controllable hydrogenation.

Poster-62

Chemical degradation of OLED host materials: The role ofexcited carriers in non-local interaction
Seunghyun Lee,1,2 Noejung Park,2 and Junhyeok Bang1,*
1

Spin Engineering Physics Team, Korea Basic Science Institute (KBSI),
Daejeon 305-806, Republic of Korea
2
Department of Physics, Ulsan National Institute of Science and Technology(UNIST), UNIST-gil 50, Ulsan 44919, Republic of Korea*

E-mail: jbang0312@kbsi.re.kr

Despite the conspicuous advances in organic light-emitting devices (OLEDs) andeven their successful implementation in commercial displays, device degradation still
remains as the most important issues. Because degradation occurs mostly in working
conditions, the underlying mechanism is thought be linked to excited state of carriers.
While several theoretical and experimental studies have focused on the mechanisms of
OLED degradation, the microscopic role of the excited carrier remains elusive. In thiswork, using occupation-constrained density functional theory calculations, we study how
chemical degradation is driven by the excited carrier in OLED host materials. We showthat the C-N bond is a weak link of the OLED molecules both in the electronic groundand excited states, and the rupture of the bond is the main cause for chemical degradation.
While the excited carrier generally weakens the bond, the effect can be mitigated by the
non-local interaction with the other bonding and anti-bonding states. We suggest that thepresence of such a non-local interaction can contribute to an enhancement of the chemical
stability in the excited state.
This was supported by Basic Science Research Program through the National Research
Foundation of Korea (NRF) (NRF-2018R1D1A1B07044564) and KBSI grant D38614.

Poster-63

Revisiting Anomalous Hall Conductivity in BCC Iron via
First-Principles Tight-Binding Calculations using Pseudo
Atomic Orbitals
Chi-Cheng Lee,* Yung-Ting Lee, Masahiro Fukuda, and Taisuke Ozaki
Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha,
Kashiwa, Chiba 277-8581, Japan*

E-mail: cclee.physics@gmail.com

The frequency-dependent Hall conductivity in ferromagnetic bcc Fe serves as a standard
example for benchmarking the first-principles calculations based on a variety of different
approaches. So far the first-principles calculations obtained via the generalized gradientapproximation have been found to well describe the available experimental data [1,2]. In
the poster presentation, we will show that better agreement with the magnetic circulardichroism experiments can be reached once the effect of the bandwidth renormalization[3] is taken into account. We will also present how to calculate the frequency-dependent
optical conductivity based on the first-principles tight-binding Hamiltonian that is
straightforwardly obtained after finishing a self-consistent calculation using the bases ofpseudo atomic orbitals implemented in the OpenMX code [4]. In particular, a generalformula without assuming the orthonormal relation between orbitals for calculating the
momentum matrix elements needed for obtaining the conductivity based on the KuboGreenwood formula will be given. The position matrix elements will be demonstrated to
be important for delivering the exact momentum matrix elements. We note that the only
needed information in the derived formula is the position matrix element and theingredients that have already contained in the tight-binding representation, evidencing theusefulness of the derived formula.

[1] Yugui Yao et al. Phys. Rev. Lett. 92, 037204 (2004).
[2] Jonathan R. Yates et al. Phys. Rev. B 75, 195121 (2007).
[3] Tobias Schickling et al. Phys. Rev. B 93, 205151 (2016).
[4] Chi-Cheng Lee et al. Phys. Rev. B 98, 115115 (2018).

Poster-64

Topological Phases in One-dimensional Graphene
Nanoribbons
Yea-Lee Lee,1 Fangzhou Zhao,2 Ting Cao,2 Jisoon Ihm,3 and Steven G. Louie2,*
12

Korea Research Institute of Chemical Technology, Daejeon 34114, Korea
Department of Physics, University of California at Berkeley, Berkeley, California
94720, USA
3
Department of Physics, Pohang University of Science and Technology, Pohang,
Kyungbuk 37673, Korea*

E-mail: sglouie@berkeley.edu

Topology of electronic band structures has been of great interest to unusual physicalphenomena derived from topologically nontrivial Bloch band systems. Recently,
atomically thin one-dimensional graphene nanoribbons (GNRs) have been shown topossess distinct topological phases in general, characterized by a Z2 invariant. [1] In thiswork, we extend the study of GNR topological phases to various GNR geometries suchas cove-edged and chevron GNRs. [2] We then explore the consequences of having
topological phase differences at heterojunctions or ends of finite segments of such GNRs,
resulting in emergence of topologically-driven metallic states at interfaces or ends,
respectively. The topological physics in GNR systems can be developed for valuableapplications, including e.g., quantum topological band engineering and quantum
information[1] Ting Cao, Fangzhou Zhao, and Steven G. Louie, Phys. Rev. Lett. 119, 076401 (2017).
[2] Yea-Lee Lee, Fangzhou Zhao, Ting Cao, Jisoon Ihm, and Steven G. Louie, Nano Lett.
accepted (2018).

Poster-65

Revisit to the molecular Jeff ground state of lacunar spinelcompounds: A charge-density functional plus U study
Hyunggeun Lee,1 Min Yong Jeong,1 Jae-Hoon Sim,1 Hongkee Yoon,1 Siheon Ryee,1and Myung Joon Han1,*
1

Department of Physics, KAIST, Daejeon 34141, Republic of Korea*

E-mail: mj.han@kaist.ac.kr

After the discovery of the Jeff = 1/2 ground state in Sr2IrO4 [1], spin-orbit entangled Jeff
state has attracted a great deal of attention. This intriguing ground state can exhibit exotic
phases of matter such as unconventional superconductivity [2] and quantum spin liquid[3]. The previous theoretical study predicted the molecular Jeff ground state in the lacunar
spinel compounds, GaM4X8 (M = Nb, Mo, Ta and W; X = S, Se and Te) [4]. Furthermore,
RIXS (resonant inelastic X-ray scattering) experiment together with the first-principles
calculations reported the Jeff = 3/2 ground state in GaTa4Se8 [5]. Recently, it was reported
that widely-used DFT+U functional based on the spin-density could easily lead tounphysical results due to the competition between the spin-density energy and the double
counting term [6]. In order to avoid such an artifact, charge-density based DFT+U
functional was suggested to be the desirable choice. Since all the previous studies oflacunar spinel compounds were performed within spin-density framework, it is strongly
requested to re-investigate the previous results. In this study, by introducing a newparameter, Jeff-ness, we analyzed the Jeff electronic structure with respect to Hubbard U
and Hund J within charge-densty framework. As a result, we confirmed the robustness ofthe molecule Jeff ground states in the lacunar spinel compounds.
[1] B. J. Kim, H. Jin, S. J. Moon, J.-Y. Kim, B.-G. Park, C. S. Leem, J. Yu, T. W. Noh,
C. Kim, S.-J. Oh, J.-H. Park, V. Durairaj, G. Cao, and E. Rotenberg, Physical Review
Letters 101, 076402 (2008).
[2] F. Wang and T. Senthil, Physical Review Letters 106, 136402 (2011).
[3] J. Chaloupka, G. Jackeli, and G. Khaliullin, Physical Review Letters 105, 027204(2010).
[4] H.-S. Kim, J. Im, M. J. Han, and H. Jin, Nature Communications 5, 3988 (2014).
[5] M. Y. Jeong, S. H. Chang, B. H. Kim, J.-H. Sim, A. Said, D. Casa, T. Gog, E. Janod,
L. Cario, S. Yunoki, M. J. Han, and J. Kim, Nature Communications 8, 782 (2017).
[6] S. Ryee and M. J. Han, Scientific Reports 8, 9559 (2018).

Poster-66

New One-Dimensional Material Nb2Se9: Theoretical
Prediction of Indirect to Direct Band Gap Transition Due toDimensional Reduction
Weon-gyu Lee1, Sudong Chae2, You Kyoung Chung1, Seungbae Oh2, Jae-Young
Choi2,3,*, and Joonsuk Huh1,*
1

Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea.
School of Advanced Materials Science & Engineering, Sungkyunkwan University,
Suwon 16419, Republic of Korea.
3
SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University,
Suwon 16419, Republic of Korea.
2**E-mail: jy.choi@skku.edu.
E-mail: joonsukhuh@skku.edu

Dimensionality reduction of some two-dimensional transition metal chalcogenides can
produce direct band gap where three-dimensional structure shows indirect band gap.
Recently, Nb2Se9 is made as 1-dimensional structure by solid state reaction. This iscomposed of periodically stacked single-chain atomic crystals (SCAC) where the SCACs
form inorganic bulk crystals due to strong bonds within the chain but weak inter-chaininteractions. To find whether the band gap transition is occurred in this SCAC materials,
the band structures of Nb2Se9 SCACs composed of 1-7 single chains is calculated using
density functional theory. Unlike the bulk structure of Nb2Se9, that chain bundles
composed of up to 21 single SCACs would have a direct band gap. Band gap increase as
the number of chains in the bundle decreased. Accordingly, Nb2Se9 bundle SCAC with adiameter of 3.6 nm is expected that it can cause the electronic transition without being
disturbed by the phononic environment due to the direct band gap, and can be used inphotoluminescence applications.

Poster-67

Versatile physical properties in new two-dimensional van der
Waals materials composed of group IV-V elements
Seungjun Lee and Young-Kyun Kwon*
Department of Physics and Research Institute for Basic Sciences, Kyung Hee
University*

E-mail: ykkwon@khu.ac.kr

Using first-principles calculations, we introduce layered IV-V compounds as novel 2D
vdW material group with versatile physical properties. Our predicted IV-V compounds
are in the form of A2B2, where A and B are elements in group IV (C, Si, Ge, Sn) andgroup V (N, P, As, Sb, Bi), forming the similar crystal structure as those of layered IIIVI compounds, such as GaSe or InSe. We revealed that these newly proposed IV-V
compounds have two stable distinct phases, one with the mirror symmetry and the otherwith the inversion symmetry. To explore their physical properties, we evaluate theirphonon dispersion relations; electronic band structure; electrical and thermal transport
properties; and estimate activation barrier of the phase transitions. Furthermore, we
discovered the local Rashba spin splitting and topological non-trivial properties found insome of our structures containing heavy elements.

Poster-68

First-principles Investigation on Al Doping in SrTiO3
Kyeongpung Lee1 and Seungwu Han*1
1
Dept. Mater. Sci. Eng., Seoul National Univ.
* E-mail: hansw@snu.ac.kr
SrTiO3 (STO) is regarded as a representative high-k material in oxide electronics,
owing to its high mobility and dielectric constant (~300). However, because of its n-typenature and relatively small band gap (3.3 eV), Schottky barrier between the metal-STO
interface is under 1 eV, which leads to large leakage current.
It has been repeatedly reported that the intrinsic n-type nature of STO originatesfrom thermodynamically stable oxygen vacancy. The most straight forward approach tocontrol the Fermi level of STO is the acceptor doping, which reduces the n-type carrier
concentration and hence increases the Schottky barrier.
There have been many studies about the effect of extrinsic dopant on STO, and it
was found that the doping of Fe or Cr ions at Ti sites reduces the leakage current
significantly. Even though it is expected that Al doping on STO should give similar
behavior, the detailed analysis with regard to the doping effect has been hardly carriedout.
In this study, first-principles calculation on Al dopant in STO is carried out. The
defect formation energies including intrinsic defects are calculated with hybrid density
functional method. The concentration of each defect configuration and the position of the
Fermi level is found. This study will give a meaningful insight into the designing of oxide
electronic devices.

Poster-69

Poster-70

Silicon Passivation of Zigzag Graphene Edge for Spintronic
Nanosensor Applications
Juho Lee and Yong-Hoon Kim*
School of Electrical Engineering, Korea Advanced Institute of Science andTechnology (KAIST), 291 Daehak-ro, Daejeon, 34141, Korea*

E-mail: y.h.kim@kaist.ac.kr

Zigzag graphene edges can ideally host spinpolarized edge states, providing significant
potential for spintronics applications. However, because the high chemical reactivity of apure sp2 termination easily destabilizes zigzag edges, preparing well-defined zigzag
graphene edges at ambient conditions remains a formidable practical challenge. Based on
first-principles calculations, we herein demonstrate that the silicon passivation of zigzag
graphene edges is a robust method to preserve the spin-polarized edge states andfurthermore to improve their electronic connectivity with neighboring nanostructures. We
find that finite-length silicon chains are the preferable edge configurations, and they allow
the sp2-type carbon edge structure and associated spinpolarized edge states to be wellpreserved. Calculating the quantum tunneling across a DNA nucleobase located in a
nanogap between two Si-passivated zigzag graphene edges, we finally demonstrate that
the Si passivation expands the graphene edge transport channels and result insignificantly enhance spin-polarized transmissions. Pointing out that the synthetic
feasibility is well supported by several recent experiments, we propose that the Si
passivation of zigzag graphene edges will open up new avenues to develop graphenebased spintronic devices including nanosensors.

Poster-71

First-principles Calculations of Intrinsic Defect Properties in
Halide Double Perovskites for Optoelectronic Applications
Tianshu Li,1 Mao-Hua Du,2 and Lijun Zhang1,*
1

School of Materials Science and Engineering, Jilin University, Changchun 130012,
China
2
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak
Ridge, Tennessee 37831, United States*

E-mail for correspondence: lijun_zhang@jlu.edu.cn

Lead-free halide double perovskites (HDPs) with the formula of quaternary
𝐴 𝐵 𝐵 𝑋 have recently attracted intense interest as alternatives to lead-halideperovskite-based optoelectronic materials for their non-toxicity and enhanced chemical
and thermodynamic stability. In particular, a series of materials represented by
Cs2AgInCl6 and Cs2AgBiX6 (X=Cl, Br) have been successfully synthesized in experiment.
With the measured physical properties, including band gaps (2.0-3.0 eV), ultra-longcarrier lifetime (6µs for Cs2AgInCl6) and low trap density (towards 108 cm-3), these HDPs
have shown desirable potential as useful optoelectronic materials. Controlling defectproperties is of vital importance for intrinsic carrier density and transport. Therefore, acomprehensive understanding of carrier trapping at defects and carrier compensation is
crucial for the development of HDPs. In this paper, using advanced first-principle
energetics calculations, we identify deep-level defects that are detrimental to carriertransport in Cs2AgInCl6, Cs2AgBiCl6 and Cs2AgBiBr6. By evaluating defect formationenergies of intrinsic defects using different chemical potentials of composed elements,
our calculations reveal the ideal growth conditions to grow p-type Cs2AgInCl6 andCs2AgBiCl6. So they can be potentially used as p-type solar absorbers and photon
detectors. In contrast, semi-insulating Cs2AgBiBr6 with low carrier density, which isconsistent with high observed resistivity in experiment, is a promising semiconductor
radiation detection material. Our work provides valuable guidelines for further
exploration of Pb-free perovskites for diverse applications.[1]References:[1] T. Li, X. Zhao, D. Yang, M.-H. Du, and L. Zhang, Phys. Rev. Applied (2018, in press).

Poster-72

Voltage Dependence of Ni-Li Electrode on its Composition
and Structure: A Density Functional Theory Study
Wei Liu,1* Koji Shimizu,1 Emi Minamitani,1 Yasunobu Ando,2 Ryota Shimizu,3Yuki Watanabe,3 Susumu Shiraki,4 Taro Hitosugi,3 and Satoshi Watanabe1
1Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo,
Bunkyo-ku, Tokyo 113-8656, Japan

2

Research Center for Computational Design of Advanced Functional Materials,
National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono,
Tsukuba, Ibaraki 305-8560, Japan
3

4

School of Materials and Chemical Technology, Tokyo Institute of Technology,
Tokyo 152-8552, Japan

Nippon Institute of Technology, 4-1 Gakuendai, Miyashiromachi, Saitama 3458501, Japan*

E-mail: liuw@cello.t.u-tokyo.ac.jp

Recently a new prototype all-solid-state memory device has been fabricated, which
consists of Li electrode, Li3PO4, and another electrode such as Au and Ni [1]. The device
has a few states with different open-circuit voltages, which can switch using an external
applied bias. Though the switching has been demonstrated, its mechanism and the atomic
structures of different states have not been well understood yet except that the movementof Li atoms near the electrode-Li3PO4 interface must play a crucial role. In the present
study, using the density functional theory calculations, we examine the dependence ofelectrode open-circuit voltage on its composition and structure to understand theswitching mechanism of this novel device.
In this presentation, we focus on the Ni electrode, because Ni does not form alloy withLi, which is expected to make the interface structure simpler. As the first step, we consider
models without Li3PO4, more specifically, the Ni(111) slab and Ni Σ5(210) grainboundary structure. The open-circuit voltage of Ni electrode is estimated by the method
which has been widely adopted in previous studies on lithium ion batteries [2]. Our
calculation results show that sites inside the Ni electrode and at the grain boundary areenergetically unfavorable for a Li atom. On the other hand, Li atoms are energeticallystable in some cases when they are on the surface of Ni electrode. The open-circuit
voltage of Ni electrode decreases as the surface coverage of Li atoms increases. These
results suggest that the atomic structures of Ni electrode with different Li surface
coverage are likely to correspond to the states with different open-circuit voltages.

This work was supported by CREST, JST.

Poster-73

Prediction of Quantum Anomalous Hall Effect in MBi andMSb (M:Ti, Zr, and Hf) Honeycombs
Zhi-Quan Huang1, Wei-Chih Chen1, Gennevieve M. Macam1+, Christian P.
Crisostomo1, Shin-Ming Huang1, Rong-Bin Chen3, Marvin A. Albao4, Der-Jun Jang1,2,
Hsin Lin5,6,7, Feng-Chuan Chuang1,2*
1

Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan
Multidisciplinary and Data Science Research Center, National Sun Yat-Sen University,
Kaohsiung, Taiwan
3
Center of General Studies, National Kaohsiung Marine University, Kaohsiung, Taiwan
4
Institute of Mathematical Sciences and Physics, University of The Philippines Los
Baños, Laguna, Philippines
5
Institute of Physics, Academia Sinica, Taipei, Taiwan
6
Centre for Advanced 2D Materials and Graphene Research Centre, National
University of Singapore, Singapore, Singapore
7
Department of Physics, National University of Singapore, Singapore, Singapore
2+ Presenter:Gennevieve M. Macam, mmgennevieve@gmail.com*Corresponding author: Feng-Chuan Chuang, fchuang@mail.nsysu.edu.tw
The abounding possibilities of discovering novel materials has driven enhanced research
effort in the field of materials physics. Only recently, the quantum anomalous hall effect(QAHE) was realized in magnetic topological insulators (TIs) albeit existing at extremely
low temperatures. Here, we predict that MPn (M=Ti, Zr, and Hf; Pn=Sb and Bi)
honeycombs are capable of possessing QAH insulating phases based on first-principles
electronic structure calculations. The application of strain shows that HfBi, HfSb, TiBi,
and TiSb honeycomb systems possess QAHE with the largest band gap of 15 meV. In
low-buckled HfBi honeycomb, we observed decreasing Chern number with increasing
lattice constant. The band crossings occurred at low symmetry points. We found that byvarying the buckling distance we can induce a phase transition such that the band crossing
between two Hf d-orbitals occurs along high-symmetry point K2. Moreover, edge states
are demonstrated in buckled HfBi zigzag nanoribbons. This study contributes additional
novel materials to the current pool of predicted QAH insulators which have promising
applications in spintronics.
Keywords: Quantum anomalous Hall effect, Topological phase transition, TM-Bi
honeycomb, Electronic structures, First-principles calculations

Poster-74

Two-dimensional topological insulators upon substitutional
doping of monolayer VB-VIA transitional metal
dichalcogenides
Aniceto B. Maghirang III,1 and Feng-Chuan Chuang1,*
1

Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan*

E-mail: fchuang@mail.nsysu.edu.tw

Substitutional doping of two-dimensional transition metal dichalcogenides (TMDs) is ofimportance in tuning and possible enhancement of its electronic, physical and chemical
properties for vast industrial applications. Here we report a systematic first-principles
study of possible 2D topological insulator phases, also known as quantum spin Hall (QSH)
insulator, upon halogen (Cl, Br, I) or pnictogen (P, As, Sb, Bi) substitution of monolayergroup VB (V, Nb, Ta) - VIA (S, Se, Te) TMDs, including the effects of one-sidedhydrogen adsorption, for both 1T and 2H crystal structures. A structural phase transition,from 2H to 1T, was observed for all the pnictogen substituted TMDs while no structuralphase transition upon halogen substitution or hydrogen adsorption. Nontrivial phases
were obtained upon pnictogen substitution and trivial phases upon halogen substitution
and hydrogen adsorption. The topology of some transition metal dichalcogenides (TMDs)
becomes nontrivial upon pnictogen substitution, demonstrating its suitability forsynthesis on various substrates.

Poster-75

Topological Dirac Insulator in a Nonsymmorphic Circuit
LatticeHong-guk Min,1 Yun-tak Oh,1 and Youngkuk Kim1*
1

Department of Physics, Sungkyunkwan University, Suwon 16419, Korea*

E-mail: youngkuk@skku.edu

Recent development of topological band theory has allowed the exciting discoveries ofa variety of topological phases beyond condensed matter systems, including phononic,
photonic, and magnetic systems. More recently, it has been shown that the energymomentum relationship of electromagnetic waves in an electronic circuit features varius
topologically protected gapless modes, eabling the electronic circuit realization of Weylnodes [1], topological nodal lines [?], and Zak phase [2]. In the present study, we
introduce our efforts to realize a novel topological crystalline phase reffered to as the
topological Dirac insulator [3] in an nonsymmorphic circuit lattice. We construct aminimal curcuit lattice that hosts required nonsymmorphic space group and show their
topological phase using Wilson band calculations.
[3]
C.H. Lee, S. Imhof, C. Berger, F. Bayer, J. Brehm, L.W. Molenkamp, T. Kiessling,
and R. Thomale, Communications Physics 1, (2018).
[4]
T. Goren, K. Plekhanov, F. Appas, and K.L. Hur, Physical Review B 97, 041106(2018).
[5]
B.J. Wieder, B. Bradlyn, Z. Wang, J. Cano, Y. Kim, H.-S.D. Kim, A.M. Rappe,
C.L. Kane, and B.A. Bernevig, Science 361, 246 (2018).

Poster-76

First-principles study of anomalous Nernst effect in Fe3Al andrelated compounds
Susumu Minami,1* Fumiyuki Ishii,2† and Mineo Saito3
1

Graduate School of Natural Science and Technology,Kanazawa Univ.,
Kakuma, Kanazawa, 920-1192, Japan
2
Nanomaterials Research Institute (NanoMaRI), Kanazawa Univ.,
Kakuma, Kanazawa, 920-1192, Japan
3
Faculty of Mathematics nad Physics, Institute of Science and Engineering,
Kanazawa Univ., Kakuma, Kanazawa, 920-1192, Japan*

E-mail: minami@cphys.s.kanazawa-u.ac.jp†
E-mail: fishii@mail.kanazawa-u.ac.jp

The anomalous Nernst effect (ANE) has expected as a new mechanism of thermoelectric
generation systems[1].The ANE magnitude can be enhanced either by two components
as follows: (i) strong asymmetry of the anomalous Hall conductivity (AHC) along theenergy axis; (ii) large product of Seebeck coefficient and Hall angle ratio[2]. The intrinsic
contribution of AHC is induced by spontaneous magnetization[3]. It implies that large
ANE could be found in magnetic materials with large anomalous Hall effect and/or large
Seebeck effect.
Heusler compounds are one candidate materials to realize large ANE according to
the two terms (i) and (ii)[4]. D03-type Heusler alloys Fe3Al is known as theferromagnetic materials with Curie temperature of 760 K[5]. Furthermore, Fe2VAl in
which one Fe atom of Fe3Al is substituted by V atom, which is correspond to 2 holedoped per formula unit shows semiconductorlike behavior and large Seebeck coefficient(S=-180 µV/K) at room temperature[6].
In this work, we investigated carrier concentration dpendence of thermoelectric
properties on Fe3Al and related compounds Fe2MnAl, and Fe2CrAl. We have performed
first-principles calculations on Heusler compounds with OpenMX code[7]. The transport
properties has been calculated based on the semiclassical Boltzmann transport theory with
Wannier90 code[8]. We have found that a large ANE in hole-doped Fe3Al by using therigid band apprximation. In the presentation, we discuss the origin of large ANE basedon the systematic computations of thermoelectric properties.
[1] Y. Sakuraba, Scripta Mater. 111, 29 (2016).
[2] Y. P. Mizuta and F. Ishii, Sci. Rep. 6 (2016).
[3] N. Nagaosa, J. Sinova, S. Onoda, A. H. MacDonald, and N. P. Ong, Rev. Mod. Phys. 82, 1589
(2010).
[4] S. Minami, F. Ishii, Y. P. Mizuta, and M. Saito, Appl. Phys. Lett. 113, 03203 (2018).
[5] Y. Nishino, M. Kato, S. Asano, K. Soda, M. Hayasaki, and U. Mizutani, Phys. Rev. Lett 79, 1909
(1997).
[6] Y. Nishino and Y. Tamada, J. Appl. Phys. 115, 123707 (2014).
[7] OpenMX: Open source package for Material eXplorer http://www.openmx-square.org.
[8] A. A. Mostofi, J. R. Yates, Y.-S. Lee, I.Souza, D. Vanderbilt, and N. Marzari, Comput. Phys.
Commun. 178, 685 (2008).

Poster-77

Guiding Principles for Enhancing Piezoelectricity in Wurtzite
Materials: First-Principles Calculations
Hiroyoshi Momida* and Tamio Oguchi
Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka,
Ibaraki, Osaka 567-0047, Japan*

E-mail: momida@sanken.osaka-u.ac.jp

Recently, piezoelectric wurtzite materials such as ZnO and GaN have received a lot of
attention as piezotronics device materials. The wurtzite materials, especially AlN, haveanother advantage of applicability in high-temperatures such as sensors in automobile
engines, because of the good thermodynamic stability of their noncentrosymmetriccrystal structures even at high temperatures. However, the piezoelectric constants ofwurtzite-type materials are generally much smaller than those of the perovskite-typematerials such as Pb(ZrxTi1-x)O3 by a few orders. It remains a challenge to explore better
piezoelectric wurtzite materials. Among the wurtzite materials, the highest
piezoelectricity has been experimentally discovered for ScxAl1-xN (about 25 pC/N for x ~0.5). Novel low-cost materials, which are superior to ScxAl1-xN, have not beensynthesized yet as there are no clear and general materials-design criteria practicallyusable for enhancing the piezoelectricity of wurtzite materials.
In this study, we calculate longitudinal piezoelectric constants (e33) of more than a dozen
binary wurtzite materials, which are listed in the crystal structure databases, by the firstprinciples methods, and we study relations between the piezoelectric constants andseveral material parameters using the statistical-learning methods [1]. The results showthat the wurtzite materials with high e33 generally have small lattice constant ratios (c/a)
almost independent of constituent elements, and approximately expressed as e33 ∝c/a (c/a)0 with the ideal lattice constant ratio (c/a)0. We find that this simple relation also
holds for highly-piezoelectric ternary materials such as the calculated e33 values of ScxAl1xN [2]. Therefore, this material-design criterion can be applicable to the case in doped
ternary materials. Based on the insight above, we have conducted a computational searchfor highly-piezoelectric wurtzite materials by identifying materials with smaller c/a.
Effects of in-plane strain on piezoelectricity of AlN, element-combination effects in LiX(X = halogen elements), and element-doping effects into ZnO are examined. The resultshows that the piezoelectricity of ZnO can be significantly enhanced by partial
substitutions of Zn with Ca. Though the calculated value of e33 of CaxZn1-xO is still
smaller than that of ScxAl1-xN, we expect that CaxZn1-xO is at a definite advantage inmaterials cost and natural resource in abundance of constituent elements.
[1] H. Momida and T. Oguchi, Appl. Phys. Express 11, 041201 (2018).
[2] H. Momida, A. Teshigahara, and T. Oguchi, AIP Adv. 6, 065006 (2016).

Poster-78

Magnetic States and Intervalence Charge Transfer of Ti and
Fe Defects in α-Al2O3: The Origin of the Blue in Sapphire
Sutassana Na Phattalung,1, * Sukit Limpijumnong,2 Jiraroj T-Thienprasert,3 andJaejun Yu4
1

Division of Physics, School of science, Walailak University, Tha Sala District,
Nakhon Si Thammarat, Thailand
2
School of Physics and NANOTEC-SUT Center of Excellence on Advanced
Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima,
Thailand3
Department of Physics, Kasetsart University, Bangkok, Thailand
4
Center for Theoretical Physics, Department of Physics and Astronomy, Seoul
National University, Seoul, Korea*

E-mail: sutassana@gmail.com

Aiming to identify the spin configuration and its alignment of Ti and Fe of ground-state
configuration in blue sapphire, we investigate various spin configurations of Ti and Fe in
Al2O3 in search of the spin configuration which give the lowest energy. To examine theelectronic, energetic, and structural properties, we perform first-principles densityfunctional-theory calculations within the PBEsol generalised gradient functional withadding Hubbard U potential. From the total energy results, we show that the high-spinstate of TiIV-FeII with an anti-ferromangetic alignment between Ti and Fe is the groundstate for both edge- and face-sharing orientations. Among several meta-stable states,
the high-spin state of TiIII-FeIII with an anti-ferromagnetic alignment is connected to the
TiIV-FeII ground state. An optical transition from the highest occupied Fe defect levelto the lowest unoccupied Ti leads to an excited state of the high-spin TiIII-FeIII
configuration together with a donation of electron from FeII to TiIV. It explains that theTiIV-FeII is the ground state and the intervalence charge transfer of TiIV-FeII to TiIII-FeIII
would be responsible for the color of blue in sapphire. We find that both edge- and facesharing alignments can be found in nature since their ground state energies are different
by only 0.02 eV. However, only the edge-sharing alignment would be expected to be
the origin of the blue in sapphire. The corresponding optical excitation energies of thistransfer of edge- and face-sharing alignments are 1.99 and 1.36 eV, respectively.

Poster-79

Magnetic Dipole-dipole Energy Evaluation on 1D, 2D, and 3D
Periodicities using Density Functional Approach
Masao Obata,1,2* Indra Pardede,1 Daiki Yoshikawa,1 Nurul Ikhsan,1
and Tatsuki Oda1,2
1

Graduate School of Natural Science and Technology, Kanazawa University,
Kakuma, Kanazawa, Ishikawa 920-1192, Japan
2
Institute of Science and Engineering, Kanazawa University, Kakuma, Kanazawa,
Ishikawa 920-1192, Japan*

E-mail: obata@cphys.s.kanazawa-u.ac.jp

Magnetic dipole-dipole interaction is one important factor for determining themagnetization direction of magnets as well as the spin-orbit interaction. Furthermore, it may
also contribute to emergences of peculiar non-collinear magnetism, such as magnetic
skyrmions, multi-ferroic polarization, etc. In general, the magnetic dipole-dipole interaction
is estimated by the arrangement of atomic magnetic moments so far. However, in the casewhere there is a large spatial anisotropy in the electron spin density, reliability of thattreatment remains uncertain. Therefore, we have investigated the way of estimating magnetic
dipole-dipole energy through the spin density obtained from density functional theory [1,2,3].
Since the magnetic dipole-dipole interaction proportional to the minus third power of the
distance between the dipoles, the effect from long distances cannot be ignored. Moreover, its
long-range feature requires some special treatment for numerical evaluation, based on thedimension of periodicity and boundary condition in the target system. One can estimate themagnetic dipole-dipole energy on each dimension with a high efficiency, using the Coulomb
Green function of the respective dimension (one-, two-, or three-dimension).
As a demonstration of our implementation, we calculated the magnetic anisotropy energyof simple 1D, 2D, and 3D magnetic structures. The result provided the same value as in thecalculation with a localized spin moment model, assuming a spherical local spin density oneach atom. Apart from this, we investigated several extreme cases for checking theimplementation and reproduced the previous results successfully. In addition, we investigatedmagnetic anisotropy of the solid oxygen which is known as antiferromagnetic molecular
crystal. In the oxygen molecule, the spin density distribution much deviates from a sphericalone because of electron orbital anisotropy. We found that the spin density distribution also
plays an important role for the magnetic dipole-dipole interaction aside from those of atomic
spin alignment. Our results are in a good agreement with the experimental data, indicating a
reliability of our method. For example, in the α-phase of solid oxygen, both the spin density
distribution and spin-orbit interaction on molecule favor a direction perpendicular to themolecular axis and the crystal field originating from the magnetic dipole-dipole interaction
limits the stable direction to the b-axis which has the mirror planes of the crystal structure.
[1] T. Oda and M. Obata, J. Phys. Soc. Jpn. 87, 064803 (2018).
[2] M. Obata, M. Christivana, and T. Oda, AIP Advances 8, 101419 (2018).
[3] T. Oda, I. Pardede, T. Kanagawa, N. Ikhsan, D. Yoshikawa, and M. Obata, IEEE Trans. Magn.
55, DOI: 10.1109/TMAG.2018.2868843, (2018).

Poster-80

Three-dimensional Dirac semimetal in a nonsymmorphic
wallpaper multi-layer
Yun-Tak Oh,1 , Hong-guk Min,1 and Youngkuk Kim1*
1

Department of Physics, Sungkyunkwan University, Suwon 16419, Korea*

E-mail: youngkuk@skku.edu

Using an explicit tight-binding model and first-principles calculations, we show that athree-dimensional stack of two-dimensional layers in the p4g or pgg wallpaper grouphosts fourfold-degenerate Dirac points at time-reversal invariant momenta of theBrillouin zone, realizing the three-dimensional Dirac semimetal phase. Our Chern
number calculations support that the system hosts Dirac` points in momentum space. In
addition, we show that Doubly-degenerate doubly-degenerate Weyl nodal lines coexist
with the Dirac points in momentum space, giving rise to topological surface states. We
establish topological phase diagrams accessible from the Dirac semimetal phase via
symmetry-breaking strains. Our first-principles calculations show that the proposed 3D
Dirac semimetal phase is realized in an existing set of materials, including BaLaCuBO5
and BaLaAuBO5.

Poster-81

Efficient O(N) divide-conquer methodwith localized natural orbitals
Taisuke Ozaki, 1,* Masahiro Fukuda,1 and Gengping Jiang2
12

Institute for Solid State Physics, The University of Tokyo, Kashiwa, Japan.
College of Science, Wuhan University of Science and Technology, Wuhan, 430081,
China.
*

E-mail: t-ozaki@issp.u-tokyo.ac.jp

An efficient O(N) divide-conquer (DC) method based on localized natural orbitals (LNOs)
is presented for large-scale density functional theories (DFT) calculations of gapped andmetallic systems [1]. The LNOs are non-iteratively calculated by a low-rankapproximation via a local eigendecomposition of a projection operator for the occupied
space. Introducing LNOs to represent the long range region of a truncated cluster reduces
the computational cost of the DC method while keeping computational accuracy. The
novel O(N) method has been implementd into OpenMX DFT code which is based on
optimized localized numerical orbitals and norm-conserving pseudopotentials [2], and aseries of benchmark calculations and high parallel efficiency in a multilevel
parallelization clearly demonstrate that the O(N) method enables us to perform large-scale
simulations for a wide variety of materials including metals with sufficient accuracy inaccordance with development of massively parallel computers.

Fig. Radial distribution functions of liquids for (a) Si at 3500 K, (b) Al at 2500 K, (c) Li
at 800 K, and (d) SiO2 at 3000 K calculated by the O(N3) and DC-LNO methods.
[1] T. Ozaki, M. Fukuda, and G. Jiang, arXiv:1809.05637.
[2] http://www.openmx-square.org/

Poster-82

Simulated Scanning Tunneling Microscope Images ofIntrinsic Defects in MoTe2
Eun-Won Park,1 Miyoung Kim,1 and Hanchul Kim1,*
1

Department of Physics, Sookmyung Women’s University, Seoul, Korea*

E-mail: hanchul@sookmyung.ac.kr

Transition metal dichalcogenides (TMDCs) are layered compounds made up of X-TM-X
trilayers, where TM and X refer to transition metal and chalcogen atoms, respectively.
MoTe2 is one of the representative TMDCs and has been studied extensively due to its
high current-on/off ratio implying potential applicability in field-effect transistors [1-5].
In a previous study, intrinsic defects in the single MoTe2 trilayer were investigatedsystematically and the Te adatom on top of a Te atom was found to be the most stabledefect [6]. In this work, we studied intrinsic defects in MoTe2 three trilayers. We
performed density functional theory (DFT) calculations by using Vienna ab-initio
simulation package. We used the PBE exchange-correlation functional in conjunction
with the DFT-D3 method to describe the van der Waals (vdW) interaction between thetrilayers. We used the 5×5 surface supercell to simulate isolated intrinsic defects. We
investigated vacancies, adatoms, interstitials, and vdW gap intercalations for Mo and Te.
The most stable structure is found to be the Te adatom on top of a Te atom in both Terich and Mo-rich conditions (the corresponding defect formation energies are 1.06 and1.35 eV) in agreement with the previous study. In addition, we simulated the constantcurrent STM images for pristine MoTe2 and intrinsic defects within the Tersoff-Hamannapproximation. The simulated STM images exhibit strong bias-dependence, which canbe used as fingerprints in identifying intrinsic defects.
[1] M. Xu et al. Chem. Rev. 113, 3766 (2013).
[2] R. Kappera et al. Nat. Mater. 13, 1128 (2014).
[3] D. H. Keum et al. Nat. Phys. 11, 482 (2015).
[4] M. Chhowalla et al. MRS Bulletin 40, 585 (2015).
[5] S. Cho et al. Science 349, 625 (2015).
[6] S. Haldar et al. Phys. Rev. B 92, 235408 (2015).

Poster-83

First-principles Study of Non-thermal Phase Transition
Mechanism with Uniaxial Stress Applied Phase Transition
Material: GeTe
Hanjin Park,1 Won Jun Yang2, Dasol Kim2, Seung Jong Park2, Mann-Ho Cho2,*, andYoung-Kyun Kwon1,*
1

Department of Physics and Research Institute for Basic Sciences, Kyung Hee
University, Seoul, 130-701, Republic of Korea
2
Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749,
Republic of Korea
1, *
2, *

E-mail: ykkwon@khu.ac.kr
E-mail: mh.cho@yonsei.ac.kr

Recently, phase change materials (PCM) have attracted attention as candidate for next
generation memory device elements. But it has several problems in power consumption,
information storage capacity, energy efficiency, and so on. We use ab initio density
functional theory to investigate non thermal phase transition of a prototypical phasechange material, GeTe, induced by uniaxial strain. We focus on the rhombohedral
structure which can be interpreted as a layered strucuture, in which layers are seperated
by long bonds. It is found that GeTe layered structure experiences a phase transition fromone crytalline phase to the other crystalline one under external uniaxial tensile stress. We
identify that the latter phase is essentially regarded as another layered structure rotatedfrom the former phase through the exchange mechansm between short and long bonds.
Our electronic transport calculation also shows that the conductance changes significantly
during such phase transition, implying that uniaxial strain may induce non-thermal phasetransition in GeTe.

Poster-84

Estimation of the Effective On-Site Coulomb Interaction
Parameter U by Mapping Atomic Self-Interaction Correction
onto GGA+U for Molecules
Jae-Hyeon Parq*
School of Earth and Environmental Sciences, Seoul National University, Seoul
08826, Korea*

E-mail: parkq2@snu.ac.kr

It is known that the on-site Coulomb interaction parameter, also called as the Hubbard U
parameter, can be obtained from a density functional theory (DFT) linear-response
method [1], but this approach is not available to DFT calculation on atom-centered basis
sets because density response to a localized potential shift cannot be described due to theunclear definition of the Hubbard U values for multiple-zeta orbitals and the limit ofaccuracy reinforcement by increasing the number of basis functions.
I propose a calculation method for effective on-site interaction U parameters by taking
advantage of the relationship between GGA+U (or LDA+U) and atomic self-interaction
correction (ASIC) [2]. Because molecular orbitals containing transition metal 3d orbitals
are often close to atomic-like orbitals, the unitary matrix (transformation between KohnSham orbitals and so-called ‘localized orbitals’) elements related with the 3d orbitals canbe assumed to be square-roots of the Mulliken 3d orbital populations for molecularorbitals. From the specific unitary matrix elements, one can obtain the localized orbitals
corresponding to the 3d orbitals, which can give effective U values.
Calculated effective U values were reasonable for simple molecules containing atransition metal atom when a numerical atomic orbital code package, OpenMX was usedwith dual projectors [3]. My results are comparable to the results of the linear-response
method on plane-wave basis sets.
[1] H. J. Kulik, M. Cococcioni, D. A. Scherlis, and N. Mazari, Phys. Rev. Lett. 97, 103001(2006).
[2] C. D. Pemmaraju, T. Archer, D. Sanchez-Portal, and S. Sanvito, Phys. Rev. B 75,
045101 (2007).
[3] M. J. Han, T. Ozaki, and J. Yu, Phys. Rev. B 73, 045110 (2006).

Poster-85

Estimation computational predictions of stable phase for
antiperovskite Na3OCl via rotation of ONa6 octahedra
Tan-Lien Pham, Abdus Samad, Hye Jung Kim and Young-Han Shin *Department of Physics, University of Ulsan, Ulsan 44610, Republic of Korea*

E-mail: hoponpop@ulsan.ac.kr

Antiperovskite Na3OCl has been considered as a candidate material for solid electrolyte.
Hippler et al. reported Na3OCl in cubic phase Pm¯3m [1] but Zinenko et al. showed
unstable phonon modes at the R and M points for cubic Na3OCl [2]. In this work, we
study the structural stability of Na3OCl in terms of energy landscapes and phonon spectrawith the rotation of ONa6 octahedra. We prove that the cubic Na3OCl can be energeticallystabilized through octahedral tilts among 15 possible tilted systems consistent with
Howard and Stokes’ group-theoretical analysis of octahedral tilting in perovskites [3].
We find that all 14 tilted structures of Na3OCl are more stable than the cubic Pm¯3m by
11-16 meV per five-atom unit cell. The tilt angles along the pseudocubic [100], [010],
and [001] directions vary in the range of 2.6–9.3. While the Pnma and P21/m structuresof Na3OCl are found as the two most stable ones, only the P21/m phase has stable phonon
vibrations with a direct band gap of 3.38 eV at the G point.
[1] K. Hippler, S. Sitta, P. Vogt, and H. Sabrowsky, Acta Crystallographica Section C
46, 736 (1990).
[2] V. I. Zinenko and N. G. Zamkova, Ferroelectrics 265, 23 (2002).
[3] C. J. Howard and H. T. Stokes, Acta Crystallographica Section B 54, 782 (1998).

Poster-86

Theoretical insight into methane oxidation to methanol on
single Fe-embeded nitrogen-doped graphene
Thantip Roongcharoen,1 Nawee Kungwan, 1,*, Supawadee Namuangruk2,*
1

Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai,
Thailand2
National Nanotechnology Center (NANOTEC), 111 Thailand Science Park,
Patumthani 12120, Thailand*

E-mail: naweekung@gmail.com, supawadee@nanotec.or.th

Methane, a major component in natural gas and biogas, is an important chemical
feedstock for synthesis of methanol as more valuable compound. Methanol is renewablesource in many industries. To convert methane to methanol, there are several technologies
such as supercritical water process, plasma technology, biological process, photocatalysts, and catalytic process. Among them, catalytic process is popular approach
because the methane goes through oxidation processes under mild condition with highyield. Different types of catalysts methane oxidation such as metal-exchanged zeolites,
metal catalyst, and carbon-based catalyst have been widely investigated. Modified
graphene as one of carbon-based materials has become attractive catalysts because its
properties are suitable for example, high specific surface volume ratio, low energy
consumption, low cost, and non-toxic materials. Among the modified graphene materials,
Fe embedded on nitrogen-doped graphene (Fe-NxG; x=1,2,3) is one of the mostinteresting catalysts because it has specific active sites and can modulate the Femi-level
leading to enhancement of catalytic activity. These materials (Fe-NxG) exhibit highchemical activity in various fields for example, Fe-N3G, and Fe-N4G for oxygen
reduction reaction (ORR). However, the reactivity of Fe-NxG catalysts in methane
oxidation are not well understood. Therefore, in this work, the methane oxidation
mechanism using Fe-NxG catalysts will be systematically investigated. Finally, thereactivity of Fe-NxG will be compared with other catalysts.

Fig.1 Proposed mechanism of methane oxidation present of N2O reduction on Feembedded on functionalized graphene (Fe-NxG).
[1] Z. Zakaria, S.K. Kamarudin, Renewable and Sustainable Energy Reviews, 65(2015) 250-261.
[2] L.Yung-Chang, Nano Lett. 15 (2015),7408−7413.
[3] Q. Thalia, C. Pabitra, Molecular Catalysis 431 (2017) 9-14.

Poster-87

Graphene edge contacts to ZnO: A first-principles study
Junga Ryou and Yong-Hoon Kim*
School of Electrical Engineering and Graduate School of Energy, Environment,
Water, and Sustainability, Korea Advanced Institute of Science and Technology(KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea*

E-mail: y.h.kim@kaist.ac.kr

In spite of the attractive material properties of graphene, there still exist numerous
obstacles in employing it into the standard field-effect transistor archictecture for device
applications. As an alternative route, Yang et al. [1] recently proposed a novel barristor
device concept, a device operates based on the tunable Schottky barrier between grapheneand semiconductors. In this work, having the graphene barristor based on ZnO in mind,
we investigate several graphene/ZnO contact models using density functional theory
calculations. By adopting graphene or graphene nanoribbon (GNR) in contact withseveral ZnO surface types, we systematically study the electronic structures ofgraphene/ZnO interfaces. We particularly comapre the top- and edge-contact models, andclarify the deerimental role of Fermi-level pinning effect amplified for the graphene edge
contacts.
[1] H. Yang, J. Heo, S. Park, H. J. Song, D. H. Seo, K.-E. Byun, P. Kim, I. Yoo, H.-J. Chungand K. Kim, Science 336, 1140 (2012).

Poster-88

Model mapped RPA: first-principles method to determine a
Hubbard model Hamiltonian
Hirofumi Sakakibara,1,2* Seung Woo Jang,3 Myung Joon Han,3 and Takao Kotani1
1Dept. of Applied Mathematics and Phisics, Tottori University, Tottori, Japan
Computational Condensed Matter Physics Laboratory, RIKEN, Saitama, Japan
3
Dept. of Physics, Korea Advanced Institute of Science and Technology (KAIST),
Daejeon, Korea
2*E-mail: sakakibara.tottori.u@gmail.com

Curious physical phenomena such as superconductivity may often be driven byelectron correlations. Such correlations are usually investigated by assuming Hubbard
type models. The hopping integrals can be evaluated from first-principles calculations by
calculating Maximally Localized Wannier Functions [1]. For the evaluations of
Hubbard interactions U, the constrained random phase approximation (cRPA) is often
adopted [2,3,4]. However, cRPA contains several problems [5]. For example, interaction
parameters calculated in cRPA become finite between distant sites because cRPA
removes the metallic screenings for Coulomb interactions.
To amend such problems, we have introduced a new method named model-mapped
RPA (mRPA) [5]. The mRPA method requires the constraint W =WM on U, where W and
WM are the screened interactions calculated in first-principles calculations and Hubbard
model calculations, respectively. Owing to the constraint, we can obtain short-rangedmodel interactions. The method of mRPA may be technically simpler and theoretically
clearer than that of cRPA.
The method of mRPA also includes the procedure to remove the double counting of
one-body terms. The mean-field terms given by two-body Hamiltonians should be
removed because one-body Hamiltonian derived from first-principles contains such
effects [5]. This is crucial for multi-orbital models.
We will present the value of U assuming two-orbital model for the cuprate
superconductors La2CuO4 and HgBa2CuO4. We analyze the material dependence of U
given by the apical oxygen height [6]. Through the analysis, U obtained from mRPA
results in different tendency with cRPA. This implies that the value of U may be
ambiguous in principles.
[1] N. Marzari and D. Vanderbilt, Phys. Rev. B 56, 12847 (1997).
[2] T. Kotani, J. Phys.: Condens. Matter 12, 2413 (2000).
[3] F. Aryasetiawan et al. Phys. Rev. B 70, 195104 (2004).
[4] E. Şaşıoğlu, et al. Phys. Rev. B 83, 121101(R) (2011).
[5] H. Sakakibara et al. J. Phys. Soc. Jpn. 86, 044714 (2017).
[6] S. W. Jang et al. Sci. Rep. 6, 33397 (2016).

Poster-89

Electronic and Photophysical Properties of Derivatives of
2-Phenylbenzothiazole and 2-(2´-Hydroxyphenyl)
benzothiazole: Effect of Intramolecular Hydrogen Bonding
Rusrina Salaeh, Chattarika Sukpattanacharoen, Poowadon Chai-In
and Nawee Kungwan*
Department of Chemistry and Center of Excellence for Innovation in Chemistry(PERCH-CIC), Faculty of Science, Chiang Mai University, Chiang Mai 50200,
Thailand.
*E-mail: naweekung@gmail.com

Photophysical properties of 2-phenylbenzothiazole (PBT) denoted as a No-PT typecompound and 2-(2´-hydroxyphenyl)benzothiazole (HBT) denoted as a PT type compound
as well as their derivatives have been investigated using six different DFT and TD-DFT
methods. The B3LYP exchange-correlation functional with 20% HF exchange is found tobe the most suitable method for reproducing experimentally photophysical data. Overall,
the simulated absorption and emission spectra of all derivatives are red-shifted comparedwith their parent compounds, PBT and HBT, except emission spectrum of TPy-1 is blueshifted. Especially, TPy-3 and HTP-2, of which the carbon atoms at 4,7-positions of the
benzothiazole core are replaced by nitrogen atoms and hydrogen atoms in the 2,6-positions
are substituted by dimethylamino phenyl groups, show more red-shifted absorption spectrathan other compounds caused by lone pair electron of nitrogen atoms and electron donatinggroup that has the effect on the π-conjugated system. In addition, TPy-4 and HTP-3 also
have the similar effect on π-conjugated system. As expected, the calculated Stokes shifts of
the PT type compounds are larger than that of the No-PT type compounds, because of thetautomer formation through the excited state intramolecular proton transfer (ESIPT)
process. The potential energy curves (PECs) scanned along the proton transfer (PT)coordinate of the PT type compounds reveal that the ESIPT process is more likely toproceed in the S1 state. The ESIPT process in HBT, HTP and HTP-1 occurs with a small
barrier or barrierless, whereas that in HTP-2 and HTP-3 involves a higher barrier. The PT
barriers were found to be in the order of HTP ~ HBT > HTP-1 > HTP-2 > HTP-3. The
knowledge accumulated through these studies is expected to be useful for the rational
design of fluorescent molecular probes.

Figure 1. Photocycle of (a) molecules without proton transfer (No-PT type) and (b) molecules withintramolecular proton transfer (PT type)[1] Kwon, J. E., Park, S. Y., Adv. Mater. 2011, 23, 3615-3642.
[2] Nakagawa, T., Yamaji, M., Maki, S., Niwa, H., Hirano, T., Photochem. Photobiol. Sci. 2014, 13,1765-1772.
[3] Suzuki, Y., Yamaji, M., Maki, S., Hirano, T., J. Photochem. Photobiol. A: Chemistry 2016, 14, 9395.

Poster-90

Ferroelectricity and piezoelectricity in stable monolayers
MoC, WC, WS, and WSe
Abdus Samad, Hye Jung Kim, and Young-Han Shin*
Department of Physics, University of Ulsan, Ulsan 44610, Republic of Korea∗E-mail : hoponpop@ulsan.ac.kr
Ferroelectricity has been a rare phenomenon in the ultra-low thin films of the ferroelectricmaterials. With the aid of density functional theory calculations, we have designed
buckled hexagonal monolayers MoC, WC, WS, and WSe. These monolayers are stableenergetically and dynamically with high spontaneous out-of-plane polarization due todifferent electronegativities and their asymmetric buckled structures. e31=50.9, 39.0, 45.0,
55.4 pC/m for monolayer MoC, WC, WS, and WSe respectively. While the in-planepiezoelectric stress coefficient along the zigzag direction does not exist due to the mirror
plane along the armchair direction, a strain along the armchair direction causes highpiezoelectric stress coefficients of 1.0×103 pC/m for monolayers MoC and WC and 0.47,
0.49× 103 pC/m for WS and WSe respectively. The in-plane piezoelectric stresscoefficient for monolayer MoS2 is reported as 3.00×102 pC/m. Thus the in-planepiezoelectric stress coefficients of these monolayers are larger than the one reported for
MoS2 monolayer. The out-of-plane polarizations of these materials may be switchable
with the relatively high switching energy barriers in the range from 0.55 to 2.7 eV per
formula unit. Furthermore, we are studying the growth of these monolayers on thelayered substrates, such as graphene or MoS2 to enhance their stability and reduce thepolarization switching barriers.

Poster-91

First-principles study of electric-field induced Z2 topologicalphase transition in strained one-bilayer Bi(111)
Hikaru Sawahata,1,* Naoya Yamaguchi1 and Fumiyuki Ishii2,†
1

Graduate School of Natural Science and Technology of Science and Technology,
Kanazawa University, 920-1192, Japan
2
Nanomaterials Research Institute, Kanazawa University, 920-1192, Japan*

E-mail: sawahata@cphys.s.kanazawa-u.ac.jp†
E-mail: ishii@cphys.s.kanazawa-u.ac.jp

Electric-field induced Z2 topological phase transition is important for applications of a Z2
topological insulator. If we are able to switch from Z2 topological insulating phase to trivial
insulating phase or vice versa by the electric field, novel devices using edge spin currents could
be realized. We predicted that one-bilayer Bi(111) shows electric-field induced Z2 topologicalphase transition by first-principles calculations[1]. The bandgap is closed at the electric field E= 2.1 V/Å and one-bilayer Bi(111) shows Z2 topological phase transition from Z2 topologicalinsulating phase (E < 2.1 V/Å) to trivial insulating phase (E > 2.1 V/Å). In order torealize device applications, the critical electric field should be reduced by tuning the bandgap.
In this study, we performed fully relativistic density functional calculations of the bandgap
and Z2 topological invariant in strained one-bilayer Bi(111) shown in Fig. (a). In order tocompute Z2 topological invariant using OpenMX code [2], we have implemented FukuiHatsugai method[3] which can be applied to the system without space inversion symmetry.
Figure (b) shows the Z2 topological phase diagram of one-bilayer Bi(111) in the space of theelectric field and strain with the 3D plot of the band structure at the strain 0.5 %. The bandgapof one-bilayer Bi(111) is closed at the strain 0.5 %, and quadratic band touching[4] appears at Γ
point. Near the strain 0.5 %, the critical electric field is reduced to E < 1.0 V/Å. In the poster
session, we will present our detailed calculated results and how to implement Fukui-Hatsugai
method in OpenMX code.

Figure: (a) The structure of one-bilayer Bi(111) (b) The Z2 topological phase diagramwith the 3D plot of quadratic band touching at the strain 0.5 %[1] H. Sawahata, N. Yamaguchi, H. Kotaka, and F. Ishii, Jpn. J. Appl. Phys. 57, 030309(2018).
[2] T. Ozaki et al. http://www.openmx-square.org/.
[3] T. Fukui and Y. Hatsugai, J. Phys. Soc. Jpn. 76, 053702 (2007).
[4] K. Sun, H. Yao, E. Fradkin, and S. Kivelson, Phys. Rev. Lett. 103, 046811 (2009).

Poster-92

First Principles Investigations on a New 1111-type Fe-based
Superconductor: ThFeAsN
Smritijit Sen1 and Guang-Yu Guo1,2
1

Department of Physics and Center for Theoretical Physics, National Taiwan
University, Taipei 10617, Taiwan
2
Physics Division, National Center for Theoretical Sciences, Hsinchu 30013,
TaiwanRecent discovery of superconductivity at 30K in stoichiometric ThFeAsN compound [1], inabsence of spin density wave order [2] stipulate a possibility of non-magnetic origin of hightemperature superconductivity. In contrary to the experimental results, first principles
calculation within GGA predicts a stripe antiferromagnetic ground state in this system [3]. In
order to explore the emergence of superconductivity in ThFeAsN, we perform electronic
structure calculations within density functional theory (DFT). Our first principles electronic
structure calculations reveal the semi metallic behavior of ThFeAsN, which resembles withthat of the LaFeAsO and most of the other Fe-based superconductors. Fig. 1 depicts our
calculated orbital projected band structure of ThFeAsN in non-magnetic state. The dominanceof Fe dyz, dxz and dxy orbitals at the Fermi level is in well agreement with that of the previous
experimental as well as theoretical results [1,4].

Fig. 1: Calculated orbital projected [Fe- dyz (green), dxz (blue), dxy (red)] band structure of
ThFeAsN with GGA optimized structure in non-magnetic state.

Moreover, the role of electron-phonon coupling to superconductivity in this system isstill not known [5]. In this work we present the electronic structures of ThFeAsN andthe role of phonon in the mechanism of superconductivity in this system.
References[1]. C. Wang et al. J. Am. Chem. Soc. 138, 2170 (2016).
[2]. M. A. Albedah et al. J Alloys Compd. 695, 1128 (2017)[3]. G. Wang and X. Shi, Europhys. Lett. 113, 67006 (2016).
[4]. D. J. Singh, J Alloys Compd. 687, 786 (2016).

Poster-93

First-Principles Study of Ir Desorption from Its Low-index
Surfaces
I. Seo,1,* S. Yokota,2 Y. Imai,2 and Y. Gohda1
1Department of Materials Science and Engineering, Tokyo Institute of Technology,
Yokohama, Japan
2
ISHIFUKU Metal Industry, Soka, Japan*

E-mail: seo.i.ab@m.titech.ac.jp

Iridium is one of the metals in platinum group. Due to good mechanical properties andchemical inertness especially at high temperature, iridium is broadly used on industries,
such as crucibles for single crystal growth, spark plugs in car engines, etc. However
iridium has desorption problems[1]. Although iridium has the lowest oxygen permeability,
iridium surfaces are oxidized above 1000K, and produce gaseous oxide molecules, suchas IrO3[2]. To solve this desorption problem, fundamental understanding of thedesorption process is naturally necesarry.
In this study, we investigate oxidation of low index surfaces of iridium such as Ir(110)and Ir(111) to find energetically favorable surface oxides and its IrO3 desorption energy,
by using first-principles calculations based on density functional theory. We used
OpenMX code, which is based on norm-conserdving pseudopotentials and pseudo-atomic
localized basis functions[3]. The GGA-PBE exchange-correlation functional[4] isadopted. Since desorption process is only occurred at high temperture, we used athermodynamical method, which gives temperature dependence of the free energy or
chemical potential by combining DFT calculation with experimental thermodynamic data,
particularly useful to gas molecules. This method give us insight of the IrO3 desorption
at high temperature, in terms of the temperature dependence of the desorption energy. We
find that IrO3 desorption is energetically favorable on some iridium surfaces.

[1] H. Jehn et al. Platinum Met. Rev. 22(3) 92-97 (1978).
[2] John H. C., J. Less-Common Met. 152 35-45 (1989).
[3] T. Ozaki, Phys. Rev. B 67, 155108 (2003).
[4] J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 77, 3865 (1996).

Poster-94

The effect of strain on the phonon thermal transport
properties of the two-dimensional 2H-MoTe2
Aamir Shafique and Young-Han Shin∗
Department of Physics, University of Ulsan, Ulsan 44610, Republic of Korea∗E-mail : hoponpop@ulsan.ac.kr

The strain is a handy and useful tool to enhance the performance of the semiconducting
devices. It can tune electronic, optical, and thermoelectric properties. However, the effectof tensile strain on the phonon thermal transport of two-dimensional materials is
unpredictable because the flexural acoustic (ZA) mode becomes harder and transverse
acoustic (TA) and longitudinal acoustic (LA) modes become softened. Here, we study
strain-dependent lattice thermal conductivity and other phonon properties such as phonongroup velocity, phonon anharmonicity, phonon lifetime of the two-dimensional 2HMoTe2 using the Boltzmann transport theory for phonon coupled with the first principles
calculations. We find that the lattice thermal conductivity is reduced approximately 2.5
times at 8% tensile strain for the two-dimensional 2H-MoTe2 contrary to graphene,
germanene, silicene, germanene, and Penta-SiC2. The reduction in lattice thermal
conductivity attributes to the reduction in the phonon group velocity, the phonon heat
capacity, and the phonon scattering time. We have also evaluated the contribution of eachmode to the lattice thermal conductivity. The ZA mode contribution decreases while the
TA/LA modes contributions increase under tensile strain. These results highlight thattensile strain is a key parameter to tune the lattice thermal conductivity and other phonon
thermal transport properties of the two-dimensional 2H-MoTe2.

Figure 1: (a) Lattice thermal conductivity of monolayer 2H-MoTe2 as a function oftemperature at zero strain, and (b) total lattice thermal conductivity, showing thecontribution of the ZA and TA/LA modes to the lattice thermal conductivity at 300 K as
a function of tensile strain at 300K.

Poster-95

OpenMX interface for the Atomistic Simulation Environment
JaeHwan Shim and Jaejun Yu
Center for Theoretical Physics, Department of Physics and Astronomy, Seoul National
University, Seoul 08826, Korea
The Atomic Simulation Environment (ASE) package written in Python is aimed atproviding an easy, flexible and customizable environment for density-functional-theory(DFT) calculations. Currently, the ASE package supports interfaces over 30 Calculators
including ABINIT, SIESTA, Quantum Espresso and VASP. While most of ab initio
calculations require massive computational resources and opt for high efficiency, thePython language behind the ASE package provides a copious number of library modules
which make swift code developments possible. Here, we like to take advantage of both
the OpenMX code and the ASE/Python modules by implementing the OpenMX interface
for the ASE. For example, combining the LAMMPS and OpenMX codes, we canseamlessly perform molecular dynamics simulations without compensating coding
efficiencies. Even benchmarking the OpenMX results against VASP is a breeze. Since
the modules in ASE are highly scalable, we can utilize some of the features of ASE
modules, eg., the phonon module, for the OpenMX calculations. We hope that thisplatform can be used for combining DFT calculations. We hope that this platform can beused for combining DFT calculations with machine learning and big data, where thefamous Python modules like Spark and TensorFlow can be employed to conduct deeplearning research.
[1] Ask Hjorth Larsen, Jens Jorgen Mortensen, et al., Journal of Physics: Condensed
matter 29, 273002(2017).

Poster-96

Construction of Neural Network Potential to Study LiIon Distribution near Au(111)/Li3PO4 Interface
Koji Shimizu1*, Wei Liu1, Wenwen Li2, Yasunobu Ando2, Emi Minamitani1, andSatoshi Watanabe1,3
1

Department of Materials Engineering, The Univerysity of Tokyo, Tokyo 113-8656,
Japan
2
Research Center for Computational Design of Advanced Functional
Materials, National Institute of Advanced Industrial Science and Technology(AIST), Ibaraki
305-8568, Japan
3
Research and Services Division of Materials Data and Integrated System(MaDIS), National Institute for Materials Science (NIMS), Tsukuba 305-0047,
Japan*

E-mail: shimizu@cello.t.u-tokyo.ac.jp

Li3PO4 based materials are used for solid electrolytes in thin film Li-ion batteries.
Recently, its application as non-volatile memory devices is also being explored:
Au/Li3PO4/Li as well as Ni/Li3PO4/Li stacked structures were found to exhibit a few
different voltage states, which can be controlled by applied voltages [1]. To develop
novel memory devices using this phenomenon, understanding on Li-ion distribution
near the metal/Li3PO4 interfaces is crucially important. We had investigated these issues
using density functional theory (DFT) based molecular dynamics (MD) calculations.
However, their high computational costs hinder analysis of interface systems including
an amorphous solid electrolyte. Considering this situation, we constructed theinteratomic potentials for the Au/Li3PO4 interface system with adopting the frameworkof the high-dimensional neural network potential (NNP) [2, 3], which is expected toacheive high reliability and low computational costs simultaneously.
We constructed the four-elements NNP using the dataset obtained by DFT calculations,which includes bulk and surface structures of Au and Li3PO4, Au surfaces with Li
adatoms, and Au/Li3PO4 interface. We created 236,322 structures in total, and thesestructures were randomly divided into the training (80%) and test (20%) sets. The rootmean-square-errors of the predicted total energies were 41.3 meV/atom and 41.4
meV/atom for the training and test sets, respectively. Next, we constructed the NNP
using a little different procedure to explore the possibility of acceralating theconstruction process. First, we constructed two separate NNPs optimized for Au and
Li3PO4, respectively. We then constructed the NNP for the Au(111)/Li3PO4 systemstarting from the above two NNPs and adding the interactions of Au-Li, -P, and -O. We
found that the NNPs obtained from the two procedures show comparable accuracy,
while the second approach required less computational time for NNP optimization. This
work was supported by CREST, JST.
[1] I. Sugiyama et al. APL Mater. 5, 046105 (2017).
[2] J. Behler and M. Parrinello, Phys. Rev. Lett. 98, 146401 (2007). [3] W.
Li et al. J. Chem. Phys. 147, 214106 (2017).

Poster-97

Oxygen adsorption and oxygen dissociation on TiB2
monolayer
Mahbubul Alam Shoaib, Hamid Ullah, Mohammad Noor-A-Alam and Young-Han
Shin†
Department of Physics, University of Ulsan, Ulsan 44610, South Korea.
∗E-mail: hoponpop@ulsan.ac.kr

Boron based two dimensional crystals have many excellent properties and received rapid
developments recently. Being the neighboring atom of carbon in the periodic table, boron
resemblances to carbon as it has similarities in electronic properties and prospective
applications, such as, biological compounds and super hard materials. The open electron
shell structure of Boron lacks one electron to be half filled. Therefore, it has paved theway for Boron to combined with various transition metals to discover new 2D metal
borides. TiB2 have been studied and revealed that it has high stability and fascinating
properties. A perfect monolayer of TiB2 is found over Boron since the movement of Ti is
restricted due to it's bonding with Boron and thus they stabilizes each other. It has apossibility to be more reactive due to the metal surface in Ti whereas graphene or boro
nitrite is very inert. Oxygen being the second most abundant gas existing in the earth's
atmosphere might play an important role as a possible gas adsorbate by substantiallyaltering the properties of 2D materials based devices through doping, resulting low
performance in practical applications. A self-consistent periodic density functional theory(DFT) study is presented here on the adsorption of O and O2 and the dissociation of O2
over TiB2 monolayer. It is observed that a barrierless O2 dissociation is occurred due tothe strong interaction between the TiB2 surface and the O2 molecules approaching
towards it.

Poster-98

Open source code development for DFT + DMFT calculation:
Correlated subspace projection and analytic continuation
Jae-Hoon Sim1 and Myung Joon Han1
1

Department of Physics, Korea Advanced Institute of Science and Technology(KAIST), Daejeon, Korea*

E-mail: mj.han@kaist.ac.kr

In the strongly correlated electron systems, it is crucial to provide an appropriate
theoretical formalism that can handle many-body effects in a material-specific context.
One of the successful approaches is the dynamical mean-field theory (DMFT) combinedwith the DFT [1]. We implemented DFT+DMFT based on OpenMX, a pseudo-atomic
orbital basis DFT code [2]. The implementation is characterized as follows: i) the wide
energy window on which the hybridization function is defined, including ligand orbitals,e.g., oxygen p orbitals. ii) projection method that defines correlated subspace based on
the natural atomic orbitals (NAOs) [3]. With this NAOs-based projector, d-p
hybridization can be reasonably described. We also discuss the newly developed methods
for analytic continuation problem, the so-called maximum quantum entropy method(MQEM) [4]. We show that the results are stable for numerical parameter changes,
applying our methods to the typical transition metal oxide systems.
[1] A. Georges et al. Rev. Mod. Phys. 68, 13 (1996); G. Kotliar et al. Rev. Mod. Phys. 78,
865 (2006).
[2] http://www.openmx.org.
[3] A. E. Reed, R. B. Weinstock, and F. Weinhold, J. Chem. Phys 83, 735 (1985).
[4] J.-H. Sim and M. J. Han, arXiv:1804.01683 (submitted).
[5] M. Jarrell and J. E. Gubernatis, Physics Reports 269, 133 (1996).

Poster-99

Searching for Antiferromagnetic Topological Phases
Young-Joon Song1, Hyo-Sun Jin1, and K.-W. Lee1,2*
1Department of Applied Physics, Graduated School, Korea University, Sejong 33010,
Korea
2
Division of Display and Semiconductor Physics, Korea University, Sejong 33010,
Korea* E-mail: mckwan@korea.ac.kr

After the suggestion by Haldane[1], a realization of quantum anomalous Hall
insulator (QAHI), also called Chern insulator(CI), has been one of the challenging topics
in condensed matter. A couple of years ago, at an extremely low temperature this phasehas been realized. Without applying any external fields, CI has robust edge states that isenergy dissipation-less and fully spin-polarized in direction of its magnetization. Due tothese fascinating properties, industry and academy have thought this CI as a promising
candidate for the next generation low power consumed electronic devices. Although thisphase has been realized only in one compound a couple of years ago, this phase isobservable at an extremely low temperature. So, realistic compounds have been required
for applications.
Nowadays attempts to realize CIs in antiferromagnets (AFMs), which often are
insulators with a high Neel temperature, have initiated in theoretical studies. Our goal is
to find promising candidates of CI in AFMs, using theoretical studies based on the firstprinciples calculations. We have been focused on the buckled honeycomb lattices,consisting of (111)-oriented cubic perovskite on SrTiO3 substrate. Our results show
nonzero Chern numbers in one spin channel. It is expected a CI state to be emerged bytunable external electric fields in this AFM system.
Acknowledgements: This research was supported by NRF-2016R1A2B4009579.

[1] F.D.M. Halane, Phys. Rev. Lett. 61, 2015(1988).
[2] D. Xiao, W. Zhu, Y. Ran, N. Nagaosa, and S. Okamoto, Nat. Commun. 2, 596 (2011).
[3] Q.-F. Liang, L.-H. Wu and X. Hu, New J. Phys. 15, 63031(2013).

Poster-100

Correcting DFT problems for the spin-state of transition
metal complexes
Suhwan Song,1 Min-Cheol Kim,1 Kieron Burke,2 and Eunji Sim1,*
1

Department of Chemistry, Yonsei University, 50 Yonsei-ro Seodaemun-gu, Seoul
03722, Korea
2
School of Physical Sciences, University of California, Irvine, CA 92697,USA*

E-mail: esim@yonsei.ac.kr

We present calculations for small transition metal complexes using a recently proposed
density-corrected density functional theory (DC-DFT) method[1]. Despite its efficiency
and reasonable accuracy, density functional theory (DFT) is known to be inaccurate inproblematic cases like spin-state changing system. In case of transition metal systems,
DFT fails to give accurate spin states consistently and the energy difference between highspin and low spin states are inaccurate. Since controlling spin states in transition metal
systems experimentally is extremely difficult, one needs to use computationally costly
methods like coupled cluster and quantum Monte Carlo in order to predict preferred spinstates. Here we show Hartree-Fock DFT (HF-DFT), one of the simplest ways to perform
DC-DFT, gives prediction in spin states with accuracy comparable to coupled cluster
results while its computation cost is similar to DFT. In HF-DFT, one evaluates DFT
energy on HF densities which results in reducing density-driven error compared toconventional DFT calculation, and has shown promising results in open-shell systems.
We believe such improvement in transition metal systems could be expanded to obtaincorrect spin-densities at no more cost than standard DFT approximations and ultimately
to determine magnetization.
[1] S. Song, M-C. Kim, E. Sim, A. Benali, O. Heinonen, and K. Burke, J. Chem. Theory
Comput. 14, 2304-2311 (2018).

Poster-101

Structural and electronic properties of α-Te tubular
nanostructures: A first-principles study
Yanrong Guo1, Songyou Wang1,2, Yu Jia3 and Wan-Sheng Su4,

1Shanghai Ultra-Precision Optical Manufacturing Engineering Center,
Department of Optical Science and Engineering, Fudan University, Shanghai
200433, China
2Key Laboratory for Information Science of Electromagnetic Waves (MoE), Shanghai
200433,China
3International Laboratory for Quantum Functional Materials of Henan, Schoolof Physics and Engineering, Zhengzhou University, Zhengzhou 450001, China
4National Taiwan Science Education Center, Taipei 11165, Taiwan*

E-mail: wssu@mail.ntsec.gov.tw

We employed density functional theory to investigate the structural and electronic
properties of α-Te tubular nanostructures. These α-Te tube-like structures, similar tothat of carbon nanotubes, in armchair and zigzag types are semiconductors withmoderate band gaps. The nanotubes in armchair configurations have an indirect-todirect band gap transition as tube diameter is decreased to a specific critical tube size,
while those in zigzag configurations are always semiconductors with direct gap
independent of the tube diameter. The calculated projected density of states reveal thatsuch an indirect-to-direct band gap transition found in armchair nanotube can be
attributed to the contributions of the different p-orbitals near the VBM edges. Thesefindings are not only helpful for better understanding the physical characteristics of αTe nanotubes, but also will open up the possibility of its use in device applications.

Poster-102

Heteroatom effect on electronic and photophysical properties of
3-hydroxyquinolin-4(H)-one and its analogues enhancing
in the excited-state intramolecular proton transfer processes:
A TD-DFT study on substitution effect
Chattarika Sukpattanacharoen1, Rusrina Salaeh1, Nawee Kungwan1,2,*
1

Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200,
Thailand2
Center of Excellence in Materials Science and Technology, Chiang Mai University, Chiang
Mai 50200, Thailand*

E-mail: naweekung@gmail.com

The effect of hetero oxygen and nitrogen substituted of 3HX derivatives (3HQ, 3HF, 3HTF, and 3HSO
where X=NH, O, S, and SO2 respectively) on the electronic, photophysical properties, and excited-state
intramolecular proton transfer (ESIPT) was investigated using density functional theory (DFT) and timedependent DFT (TD-DFT). Geometries and absorption spectra as well as emission spectra of 3HX
derivatives were carried out by using DFT and TD-DFT at the B3LYP/TZVP level. The importantparameters for bond distances involving the intramolecular H-bond reveal that H-bonds of 3HX derivatives
in excited-state are stronger than those in the ground state, supported by the red-shift of O–H vibrationalmodes in the excited-state. The heteroatom substitution of 3HX causes the red-shift emission spectra,
implying that the lone pair of electron in the substituted heteroatom has the effect on the intramolecularcharge transfer. In addition, results of frontier molecular orbitals show that vertical S0→S1 transition ofthese molecules corresponds essentially to the excitation from HOMO (π) to LUMO (π*). The potential
energy curves (PECs) of intramolecular proton transfer (IntraPT) process of all derivatives were used toinvestigate the occurrence of ESIPT. The hetero sulfur on X positions of 3HX derivatives could easily
facilitate the ESIPT process because sulfur makes O1–H1 bond of 3HTF weaker than those of otherderivatives confirmed by its more red-shifted vibrational modes in the excited-state compared with otherheteroatom substitutions, resulting in lower ESIntraPT barrier. The obtained information of the electronic
structure, the photophysical property and the chance of ESIPT of heteroatom substituted 3HX molecules
are useful for the molecular design of fluorescent molecular probes.

Figure. Schematic of 3HQ, 3HF, 3HTF, and 3HSO and Schematic diagram of the general ESIPT
process, a proton donor and proton acceptor are circled with red and blue, respectively.
Keywords: Excited state proton transfer (ESPT), 3-Hydroxyquinolin-4(H)-one, Heteroatom effect, B3LYP[1] Meng, F. Y., Chen, Y. A., Chen, C. L., & Chou, P. T., ChemPhotoChem., (2018).
[2] Salaeh, R., Prommin, C., Chansen, W., Kerdpol, K., Daengngern, R., Kungwan, N., Journal of
Molecular Liquids., 252, 428-438 (2018).
[3] Zamotaiev, O. M., Shvadchak, V., Sych, T. P., Melnychuk, N. A., Yushchenko, D., Mely, Y.,
Pivovarenko, V. G., Methods Appl. Fluoresce., 4, 3, 034004 (2016).

Poster-103

First-Principles Study of Phonon Anharmonicity in CsPbBr3
Terumasa Tadano,1,* and Wissam A Saidi2
1

International Cener for Young Scientists (ICYS), National Institute for Materials
Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan2
Department of Mechanical Engineering & Materials Science (MEMS), Universityof Pittsburgh, Pittsburgh, PA 15261, USA*

E-mail: Tadano.Terumasa@nims.go.jp

Halide perovskites ABX3 (A=CH3NH3,Cs; B=Pb,Sn; X=Cl,Br,I) have attracted significant
attention in recent years for their excellent optoelectronic properties. Both organic-inorganic(A=CH3NH3) and all-inorganic (A=Cs) halides perovskites have been investigated forpotential applications in light- and energy-harvesting devices such as photovoltaics andthermoelectrics. Recent experimental studies have shown that the lattice thermal conductivity
𝜅 of CH3NH3PbI3 is unusually low (~ 0.5 W/mK), which was attributed to the rotationalmotion of the guest molecule. However, a similar value of 𝜅 has also been reported in
CsPbX3, which is free from the rotational degree of freedom of the guest molecule. While
several theoretical studies on CsBX3 have been reported so far, the origin of the ultralow 𝜅is still an open question.
To elucidate the microscopic origin of the ultralow 𝜅 of halide perovskites, we haveinvestigated phonon anharmonicity and thermal conductivity of CsPbBr3 by using accurate
first-principles methods. To see the effect of the structural phase transition on phonon
anharmonicity, we have compared thermal conductivities of three different phases of
CsPbBr3: cubic, tetragonal, and orthorhombic (see Fig.). For the high-temperature phases, wehave conducted the self-consistent phonon (SCP) calculations [1,2] to obtain the well-definedstable phonons at finite temperature. We will show the temperature dependence of phonon
frequencies and lattice thermal conductivity of CsPbBr3 and discuss the origin of the ultralow
𝜅 .

Figure: Calculated phonon dispersion curves of three phases of CsPbBr3.

[1] T. Tadano and S. Tsuneyuki, Phys. Rev. B 92, 054301 (2015).
[2] T. Tadano and S. Tsuneyuki, J. Phys. Soc. Jpn. 87, 041015 (2018).

Poster-104

Variance of GNR FET characteristics caused by Anderson
localization phenomena
Kengo Takashima1, Takahiro Yamamoto1, 2
12

Department of Engineering, Tokyo University of Science, Tokyo 125-8585, Japan
Department of Liberal Arts, Tokyo University of Science, Tokyo 125-8585, Japan
E-mail: takahiro@rs.tus.ac.jp

Graphene is expected to be a channel material of field effect transistors (FETs) becauseof its high carrier mobility. However, no band gap of the graphene is a serious problem
for its FET application. One possible way to overcome the gap-opening problem is toprocess it in the form of a nanometer width ribbon, referred as graphene nanoribbons(GNRs). They have been successfully applied to FETs with high on-off ratio. Although
the resistance of GNR is known to increase dramatically with edge disorder[1][2], theeffects of edge roughness on the FET characteristics (e.g., on-off ratio and subthreshold)have not been clarified yet.
In this study, we have investigated the coherent electronic transport in edge-disorderedarmchair GNR FETs (ED-AGNR-FETs) using the nonequilibrium Green’s function
method combined with a tight-binding model[3]. In our simulation model, the edge
roghness is modeled by adding or removing pairs of carbon atoms at the edges (Fig. 1).
We calculated drain current(Id) versus gate voltage(Vg) characters of ED-AGNR-FETs bychanging the roughness concentration P from 0% to 30% and the ribbon-width from
2.21nm (Fig. 2). We confirmed that average values of device characteristics deteriorated
with increasing of P. However, even for P = 30%, some GNR-FETs show that subthreshold slope values are smaller than 60mv/dec which is the limit value of planer FET
as considered here. Furthermore, we investigate optimal position of edge roughness toimprove FET characteristics.

Fig. 1

Edge-disordered AGNR-FET

Fig. 2 Id-Vg curves of edge-disordered AGNR-FETs[1] K. Takashima and T. Yamamoto, APL., 104, 093105 (2014).
[2] K. Takashima, S. Konabe and T. Yamamoto, JAP., 119, 024301 (2016).
[3] P. Koskinen and V. Mäkinen, Computational Materials Science, 47, 237 (2009)

Poster-105

Poster-106

Surface effects in the (001) BaTiO3 ferroelectric slab fromfirst-principles calculations and phase field simulation
Viet-Dung Tran, Hye Jung Kim and Young-Han Shin1
1

Department of Physics, University of Ulsan, Ulsan 44610, Republic of Korea*

E-mail: hoponpop@ulsan.ac.kr

We have investigated out-of-plane polarization in the (001) ferroelectric BaTiO3 slab
using first-principles and phase-field calculations. In the phase-field simulation, thechange of polarization near the surface by the surface relazation effect has been modeledusing an extrapolation length. The effects of BaTiO3 slab size, surface terminations (BaO
and TiO2 terminated surfaces) and value of extrapolation lengths have been obtained fromab initio calculations on the basis of density functional theory. By combining with phasefield simulation based on Landau-Ginzburg theory[1], it was found that the polarizationof ferroelectric thin films is dependent fully on the extrapolation length of films.
[1] J. Wang, T.Y. Zhang, Phys. Rev. B, 73 144107 (2006).

Poster-107

Secondary Electron Emission from Multi-layer Graphene by
TDDFT Simulations
Yoshihiro Ueda, Yasumitsu Suzuki, and Kazuyuki Watanabe*
Department of Physics, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku,
Tokyo 162-8601, Japan*

E-mail: kazuyuki@rs.kagu.tus.ac.jp

Scanning Electron Microscopy (SEM) that observes secondary electron emission (SEE)
has great achievements in surface science. However, the physical interpretation of SEM
images, especially, of atomic sheets such as graphene is not clear. Some experiments
comparing the amount of SEs before and after coating graphene on the substrates havebeen reported, and it has been found that graphene coating decreases the amount of SEs[13]. However, the mechanism of SEE from graphene itself is totally unkown because it isdifficult to distuinguish experimantaly SEE of the graphene from that of the substrates.
Therefore, a theoretical study of SEE from graphene is worth doing for clarifying theunderlying mechanism of SEE leading to the SEM images.
A time-dependent density functional theory (TDDFT) simulation in real time has beensuccessfully applied to electron wave-packet scattering by graphene in our previous
studies[4-7]. The present TDDFT study enables a fully dynamic description of both thetarget and incident electrons, which is necessary for modeling nanostructures. Comparedwith the conventional scattering theory, the TDDFT method has an advantage in thatmultiple and inelastic scatterings are automatically included in the simulations.
In this study, we investigated SEE of multi-layer graphene (MLG) by the TDDFT
simulations, and determined the incident energy dependence and the layer-number
dependence of SEs from MLG. The amount of SEs tends to converge to a certain value
with the increase of the number of layers, especialy, upon low-energy (< 200 eV) electron
impact. The convergence originates from attenuation of incident electron and relationshipbetween the amount of bound excited electrons and total excited electrons[8]. Finally, we
determined the SEE of bulk graphite that is comaparable to the experiment[9].
[1] M. Cao et al. Diamond Relat. Mater. 73, 199 (2017).
[2] P. Riccardi et al. Appl. Phys. Lett. 97, 221909 (2010).
[3] K. Shihommatsu et al. ACS omega 2, 7831 (2017).
[4] K. Tsubonoya, C. Hu and K. Watanabe, Phys. Rev. B 90, 035416 (2014).
[5] Y. Ueda, Y. Suzuki and K. Watanabe, Phys. Rev. B 94, 035403 (2016).
[6] H. Miyauchi, Y. Ueda, Y. Suzuki and K. Watanabe, Phys. Rev. B 95, 125425 (2017).
[7] Y. Ueda, Y. Suzuki and K. Watanabe, Phys. Rev. B 97, 075406 (2018).
[8] Y. Ueda, Y. Suzuki and K. Watanabe, Appl. Phys. Express 11, 105101 (2018).
[9] J. Cazaux, J. Phys. D 38, 2442 (2005).

Poster-108

Defective SnS monolayer as a candidate for long-range
ferromagnetism
Hamid Ullah, Mohammad Noor-A-Alam, Hye Jung Kim, and Young-Han Shin∗
Department of Physics, University of Ulsan, Ulsan 44610, Republic of Korea∗

E-mail : hoponpop@ulsan.ac.kr
We investigate the formation and migration of vacancies at both tin (Sn) and sulfur(S) sites in SnS monolayer using first principles calculations. Since the vacancy formation at the Sn site (4.75 eV/Sn) is more probable than that at the S site (6.03 eV/S), we
expect that the Sn vacancies will be more likely to be observed in experiments. Due tothe high vacancy migration energy barrier, we expect that the S vacancy will remain at
the position where it is created, reducing the formation of vacancy clusters. SnS
monolayer remains non-magnetic with the creation of both Sn and S vacancies. To induce magnetism in SnS, we replace Sn with transition metals (TMs = Mn, Fe, Co) andfind a significant influence on the electronic and magnetic properties of monolayer SnS.
The doping of TM alters the non-magnetic nature of SnS monolayer into magnetic one,but keeps it semiconducting. Additionally, long-range ferromagnetic behaviors are observed for all the doped systems. Hence, the addition of TM in monolayer SnS could be a
promising process to realize two-dimensional diluted magnetic semiconductors. Moreinterestingly, all the doped configurations show a high spin state, which can be used innanoscale spintronic applications such as spin-filtering devices. [1, 2][1] L. C. Gomes and A. Carvalho, Phys. Rev. B 92, 085406(2015).
[2] Ullah et al. J. Appl. Phys. 124, 065102 (2018).

Poster-109

Thickness Dependent Electronic Properties of Pt
Dichalcogenides – PtX2 (X = S, Se, and Te)
Rovi Angelo B. Villaos1, Christian P. Crisostomo1, Zhi-Quan Huang1,
Shin-Ming Huang1, Allan Abraham B. Padama2, Marvin A. Albao2, Hsin Lin3,
Feng-Chuan Chuang1*
12

Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan
Institute of Mathematical Sciences and Physics, College of Arts and Sciences,
University of the Philippines Los Baños, College, Laguna, Philippines
3
Institute of Physics, Academia Sinica, Taipei, Taiwan*

E-mail: fchuang@mail.nsysu.edu.tw

Using first-principles calculation, we explore the tunability of the electronic properties of
PtX2 (X = S, Se, and Te) with respect to the film thickness. We examine different known
structures, including 1T, 2H, and 3R. For bulk and layered structures (1 to 10 layers),
octahedral 1T is the most stable. Surprisingly, we also find that the 3R structure hascomparable stability relative to the 1T, implying possible synthesis of 3R. For a bulk 1T
structure, PtS2 is semiconducting with an indirect band gap of 0.25eV, while PtSe2 andPtTe2 are both semi-metallic. Still, all their corresponding monolayers exhibit an indirect
semiconducting phase with band gaps of 1.68eV, 1.18eV, and 0.40eV for PtS2, PtSe2, and
PtTe2, respectively. For the layer dependence of band properties, we observe that all PtX2transition metal dichalcogenides (TMDs) manifest decreasing/closing of indirect bandgap
with increasing thickness, a consequence of quantum confinement and interlayerinteraction. Moreover, we discover that applying strain can manipulate van Hove
singularity resulting to high density of states at the maximum valence band. Our results
show that the sensitivity and tunability of electronic properties of PtX2 pave a new pathfor future potential applications.

Poster-110

Poster-111

Local work functions of clean tungsten surfaces under electricfields based on ab initio calculations
Yue Wang,1 Liangliang Xu,1 Ming-Chieh Lin,1,* and T. C. Leung2
1Multidisciplinary Computational Laboratory, Department of Electrical and Biomedical
Engineering, Hanyang University, Seoul 04763, Korea
2
Department of Physics, National Chung Cheng University, Chia-Yi 62101, Taiwan*

Corresponding author: mclin@hanyang.ac.kr

Tungsten, the common choice for vacuum tube filaments, can survive under hightemperatures and provide thermionic emission of electrons. However, the emission islargely limited due to its relatively high work function (approximately 4.5 eV). First
principles or ab initio calculations are used to study the local work functions of tungsten(W) clean (100), (110), and (111) surfaces under external electric fields. The authorscarefully and systematically tested the convergence of density-functional-theory (DFT)
calculations in the local-density approximation (LDA) or generalized-gradientapproximation (GGA) with a plane-wave basis set the projector-augmented wave method
as implemented in the Vienna ab-initio simulation package (VASP). Several
pseudopotentials have been tested for comparion. With the tungsten model under electricfields applied on both sides, we can investigate the dependence of the local work functionand effective work function on field strength. In addition to thermionic emission, tungsten
has been considered for use as a field emission (FE) electron source.
[1] M. C. Lin, R. F. Jao, and W. C. Lin, J. Vac. Sci. Technol. B 26, 821 (2008).
[2] T. C. Leung, C. L. Kao, and W. S. Su, Phys. Rev. B 68, 195408 (2003)[3] T. W. Pi, I. H. Hong, and C. P. Cheng, Phys. Rev. B 58, 4149 (1998).

Poster-112

Prediction of Large-Gap Topological Insulator in
Functionalized Ordered Double Transition Metal MXene
Mei-Ling Xu1,＋ , Zhi-Quan Huang1, Gennevieve Macam1, Chia-Hsiu, Hsu1, FengChuan Chuang1,*
1

Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan+Presenter: Mei-Ling Xu, b042030009@g-mail.nsysu.edu.tw*Corresponding Author: Feng-Chuan Chuang, fchuang@mail.nsysu.edu.tw

MXenes have become popular 2D materials in the recent years owing to theirvarious composition and surface functional possibilities. Though numerous MXenes werepredicted to possess topological properties [1-3], the exploration of topological phase in
MXenes is still ongoing. Here, we conduct a rigorous search study on V2TiC2 with various
surface terminations, X2 (X = F, Cl, I, Br, O, H, and OH) using first-principles
calculations. We find that V2TiC2F2 is a topological insulator determined from thecalculations of the topological invariant and the parities of wave functions at the time
reversal invariant momentum (TRIM) points of the Brillouin zone below the fermi level.
It has a non-trivial band gap of 40 meV and 251 meV using GGA and hybrid functionals,
respectively. Further analysis shows that majority of the contribution of band inversion
are from the d-orbitals of V atoms. We also find that V2TiC2F2 remains a robust
topological insulator against tensile strain up to 19%. The combined unique properties of
topological insulators and MXenes makes it a valuable 2D material worth of further study
with a potential to play an important role in the development of technology.
[1] Hongming Weng, Ahmad Ranjbar, Yunye Liang, Zhida Song, Mohammad Khazaei,
Seiji Yunoki, Masao Arai, Yoshiyuki Kawazoe, Zhong Fang, and Xi Dai, Large-gap
two-dimensional topological insulator in oxygen functionalized MXene. Phys. Rev. B
92 075436 (2015).
[2] H. Mohammad Khazaei, A. Ranjbar, M. Arai, and S. Yunoki, Topologicalinsulators in the ordered double transition metals M'2M"C2 MXenes (M' = Mo, W; M"= Ti, Zr, Hf). Phys. Rev. B 94 125152 (2016).
[3] C. Si, K. H. Jin, J. Zhou, Z. Sun, and F. Liu, Large-Gap Quantum Spin Hall State in
MXenes: D-Band Topological Order in a Triangular Lattice. Nano Lett. 16, 6584
(2016).

Poster-113

First principles study on electronic properties of magnetite forspin polarized electron emission
Liangliang Xu,1 Nan Zhao,1 Ming-Chieh Lin,1,* and T. C. Leung2,
1

Multidisciplinary Computational Laboratory, Department of Electrical and Biomedical
Engineering, Hanyang University, Seoul 04763, South Korea
2
Department of Physics, National Chung Cheng University, Chia-Yi 62101, Taiwan*

Corresponding author: mclin@hanyang.ac.kr

Magnetite is a mineral and one of the main iron ores. With the chemical formula Fe3O4,
it is one of the oxides of iron. Magnetite is the earliest discovered magnet, around 1500
B.C. It crystallizes in the inverse cubic spinel structure (Fd3m) above the so-called
Verwey transition temperature which is about 120 K. It has been found that a hightemperature phase magnetite has a negative polarization of 100% at the Fermi surface,i.e., near the Fermi surface, only the spin down subband exists and the spin-up subband
is far away from the Fermi surface. As a half-metallic material, Fe3O4 shows normal
metallic behavior in the minority spin, while at the same time there is a gap of about 0.5
eV in the majority spin at the Fermi level. Although extensive studies of magnetite withconsiderable effort have been carried out over the past decades, the interesting electronic,
magnetic, and transport properties as well as the potential industrial applications inmagnetic multilayer devices, magnetite has still attracted much attention in recent years.
In this work, we study the electronic properties of magnetite using first principles or abinitio calculations based on density functional theory in order to investigate a spinpolarized electron emission. The work functions of magnetite Fe3O4 on different surfaces
have been determined. In addition, local work functions have been analyzed and thecorrespondences with electron charge density distribution have been found. With thisapproach, one can investigate spin polarized properties of different materials such as
ferrite accurately and efficiently. The magnetite as a half-metal can possibly be used as afield emitter for generating a spin polarized electron emission which may help in future
analysis of noninvasive surface probes for biological systems or nanoelectronics.
[1] H. T. Jeng and G. Y. Guo, Phys. Rev. B 65, 094429 (2002).
[2] J. Noh, O. I. Osman, S. G. Aziz, P. Winget, and J.-L. Brédas, Chem. Mater. 27, 58565867 (2015).
[3] T. Pabisiak, M. J. Winiarski, T. Ossowski, and A. Kiejna, Phys. Chem. Chem. Phys.
18, 18169 (2016).

Poster-114

First-Principles Study on Surface States of Rocksalt SnSe
Kunihiro Yananose1 and Jaejun Yu1,*
1

Department of Physics and Astronomy, Seoul National University, Seoul, Korea*

E-mail: jyu@snu.as.kr

The rocksalt SnSe compound is known as the topological crystalline insulator in which
the gapless surface state is protected by the non-trivial mirror Chern number of (110)
mirror plane. In the absence of the spin-orbit coupling, however, it becomes a topologicalnodal line semimetal. The nodal line is a line of degenerate points in the k-space between
the conduction and the valence bands. In this study, we explore the nodal line structure
in rocksalt SnSe. We calculate the Zak phase of SnSe and verify that the Zak phase isquantized and jumps by π at the nodal line, which is consistent with Ref. [2]. Zak phase
is a Berry phase integrated along the straight line in Brillouin zone. Recently, the bulk
boundary correspondence for nodal-line semi-metal using Zak phase was suggested that
there is drum-head like flat surface band in the region of π-Zak phase. However, some
exceptions was also reported. In that context, we calculate the surface states of SnSe withand without spin-orbit coupling and check the bulk-boundary correspondence. Further,
we explore the condition such as passivation and relaxation that reproduces theexperimentally observed Dirac cone at gamma-bar point of SnSe (111) surface. There isno surface state at gamma-bar point in the calculation of pristine SnSe.

[1] Y. Sun, Z. Zhong, T. Shirakawa, et. al., Phys. Rev. B 88 235122 (2013).
[2] M. Hirayama, R. Okugawa, T. Miyake, et. al., Nat. Commun. 8 14022 (2017).
[3] W. Jin, S. Vishwanath, J. Liu, L. Kong, et. al., Phys. Rev. X 7 041020 (2017).
[4] Z. Wang, J. Wang, Y. Zang, et. al., Adv. Mater. 2015, 27 4150-4154 (2015).
[5] S. Eremeev, Y. Koroteev, I. Nechaev, et. al., Phys. Rev. B 89 165424 (201

Poster-115

Electrochemical potential profiles within non-equilibrium
nanoscale junctions from first principles
Hyeonwoo Yeo,1† Juho Lee, 1† Han Seul Kim,2 and Yong-Hoon Kim1*
1

School of Electrical Engineering and Graduate School of Energy, Environment,
Water, and Sustainability, Korea Advanced Institute of Science and Technology(KAIST), 291 Daehak-ro, Daejeon, 34141, Korea

2Center for Division of National Supercomputing Research and Development, Korea
Institute of Science and Technology Information (KISTI), 245 Daehak-ro, Yuseong-gu,
Daejeon 34141†
These authors contributed equally to this work*

E-mail address: y.h.kim@kaist.ac.kr

Reliable first-principles simulations of nonequilibrium junction systems at finite bias
voltages is highly desirable for the understanding of open quantum systems anddevelopment of next-generation nano-electronic/energy/bio devices. While the nonequilibrium Green’s function (NEGF) formalism based on density functional theory (DFT)
output has been established as the standard approach for this purpose in the past decadeor so, it suffers from several intrinsic shortcomings. We have recently developed a multispace constrained search density functional theory (MS-DFT) formulation for
nonequilibrium quantum transport calculations and revealed the atomistic origins ofnegative differential resistance appearing in van der Waals heterojunction transistors
based on graphene electrodes [1]. In this presentation, taking molecular junctions as test
systems, we first systematically compare DFT-NEGF and MS-DFT and establish thepractical equivalence between the two formalisms. An important feature of MS-DFT thatdifferentiates it from DFT-NEGF is that it relies on the determination of electrochemical
potentials or quasi-Fermi levels across the channel, which are not explicitly provided
within DFT-NEGF unlike their electrostatic potential counterparts. Analyzing the spatial
profiles of electrochemical potentials for different molecular channel cases, we extract
important insights into the nature of nonequilibrium quantum transport in nanoscale
devices. The integrated microscopic information will provide critical insights on thebiased nanoelectrode interfaces, opening new avenues toward the study of nanoelectronic/energy/bio devices.
[1] H. S. Kim and Y.-H. Kim, arXiv:1808.03608 [cond-mat.mes-hall].

Poster-116

Vibrational effects on the surface energy of III-V compound
semiconductors using ab-initio thermodynamics
In Won Yeu1,2, Gyuseung Han1,2, Cheol Seong Hwang2, and Jung-Hae Choi1,*
1Center for Electronic Materials, Korea Institute of Science and Technology, Seoul
02792, Korea
2
Department of Materials Science and Engineering, and Inter-university Semiconductor
Research Center, Seoul National University, Seoul 08826, Korea*

E-mail: choijh@kist.re.kr

The surface energy is important in understanding the surface structure and crystal shapewhich are crucial to design materials for various applications. The conventional density
functional theory (DFT) provided a method to obtain the surface energy, , as a functionof chemical potential, . One of the main difficulties of using () is that it cannot bedirectly compared with the experimental results because (i) () is the electronic energy
difference of the ground state; (ii) it is almost impossible to control  through theexperimental variables of temperature (T) and pressure (P); and (iii) the surface
vibrational and configurational entropy effects which are calculated as a function of T
cannot be consistently combined with ().
We reccently estabilished a thorough method to calculate the surface energy as a functionof T and P by combining DFT and thermodynamics [1]. In addtion, the surface energy
including the effects of surface vibration was obtained for the typical III-V compounds,
such as GaAs and InAs by considereing various reconstructions with different
stoichiometry and bonding geometry. As a result, we confirmed that some reconstructions
which are unstable in terms of electronic surface energy become energetically stable athigh T due to the surface vibrational effects. The calculation results were compared withthe previous experimental works and showed good agreements. Such a correspondenceof the calculations and experiments for a given T and P has not been available in theprevious DFT calculations.
[1] In Won Yeu et al. Sci. Rep. 7, 10691 (2017).

Poster-117

Analytic continuation via “domain-knowledge free” machinelearning
Hongkee Yoon1, Jea-Hoon Sim1, and Myung Joon Han1,*
1

Department of Physics, Korea Advanced Institute of Science and Technology(KAIST), Street Address, Korea*

E-mail: mj.han@kaist.ac.kr

We present a machine-learning (ML) approach to a long-standing issue in quantum
many-body physics, namely, analytic continuation. This notorious ill-conditioned
problem of obtaining spectral function from Matsubara Green's function has been a focusof new method developments for past decades. Therefore, many crafty approaches exist;
such as maximum entropy method [1,2], stochastic method [3], Pade’s approximation [4].
These approaches require a deep understanding of the details of the problem. We call thisdetail as ‘domain-knowledge’; such as physical/mathematical approximations andassumptions. Here we show that the ML-based kernel can be realized without ‘domainknowledge’, using modern ML techniques [5], e.g. convolutional neural network (CNN)
and Adam optimizers [6]. Furthermore, the ML-based kernel is more robust to noisefrom Green’s function. We will also examine the possibility of extending the ML-based
analytic continuation to the matrix-valued continuation problem, which recently beentackled by maximum quantum entropy method (MQEM) [7]. Our results illustrate that
the ML approach can be a new direction to solved ill-posed physical problem.
[1] Jarrell, M. & Gubernatis, J. E. Bayesian inference and the analytic continuation ofimaginary-time quantum Monte Carlo data. Physics Reports 269, 133–195 (1996).
[2] Bergeron, D. & Tremblay, A.-M. S. Algorithms for optimized maximum entropy anddiagnostic tool for analytic continuation. Phys. Rev. E 94, 023303 (2016).
[3] Sandvik, A. W. Stochastic method for analytic continuation of quantum Monte Carlodata. Phys. Rev. B 57, 10287 (1998).
[4] Vidberg, H. J. & Serene, J. W. Solving the Eliashberg equations by means of N-point
Padé approximants. J. Low Temp. Phys. 29, 179 (1977).
[5] H. Yoon, J.-H. Sim, and M. J. Han, ArXiv1806.03841 Cond-Mat Physics (2018).
[6] D. P. Kingma and J. Ba, ArXiv14126980 Cs (2014).
[7] Sim, J.-H. & Han, M. J. Maximum Quantum Entropy Method. ArXiv1804.01683
Cond-Mat (2018).

Poster-118

First-Principles Density Functional Study in the Magneticallyand Electrically Polarized Pt/CoO/ZnO
Daiki Yoshikawa,1* Masao Obata,1,2 Indra Pardede,1 and Tatsuki Oda1,2
1

Graduate School of Natural Science and Technology, Kanazawa University,
Kakuma, Kanazawa, Ishikawa 920-1192, Japan
2
Institute of Science and Engineering, Kanazawa University, Kakuma, Kanazawa,
Ishikawa 920-1192, Japan*
E-mail: yoshikawa@cphys.s.kanazawa-u.ac.jp
Non-volatile and low-energy-consumption memory, for examples, Magnetoresistive Random
Access Memory (MRAM) or Ferroelectric RAM (FeRAM), has been investigated for over ten
years. Recently the junction of CoPt/MgZnO was fabricated and investigated as an interesting
hybrid [1]. Atomic layer stacking of CoPt has a large magnetic anisotropy energy (MAE) becauseof large spin-orbit interaction (SOI), and wurtzite-ZnO can provide a spontenious electric
polarization depending on its surface edge. The CoPt magnetic metal with ZnO-based tunnel
junction is a candidate of materials for the new device hybridizing MRAM and FeRAM. The
electronic structure at the ferromagnetic/ferroelectric interface is so mysterious that themechanism of interaction between ferromagnetics and ferroelectrics has still been veiled.
We investigated electronic structure of Pt(111)/CoO/ZnO(0001) slab system by using a firstprinciples calculation based on density functional theory. The method covers the effects ofmagnetic and electric polarizations for slabs [2,3]. To analyse modulation with respect to theelectric polarization direction of ZnO, we considered that two ZnO structures; Zn adjacent to CoO
plane as P+, and O adjacent to CoO as P-. The in-plane lattice constant was fixed a ZnO value
extracted from the bulk and we induced out-of-plane structural relaxation for P+ and P-,
respectivly. After a self-consistent computation, we confirmed both a spin polarization in PtCo
layer and a spontenious electric polarization of ZnO, simultaneously. The direction of P+ istoward CoO, and the direction of P- is opposite. In each resulting slab, the electric polarizationof ZnO is cancelled out by the electrostatic potential to fulfill a Poisson’s equation. The resultshows that in P+ electrons around CoO tend to sweep out to ZnO side (electron depletion state).
On the other hand, electrons in P- is attracted to CoO side (electron accumulation state). This isconsistent with the number of electrons in Co atomic sphere. We also analysed partial density ofstates (PDOS). There are large exchange splittings in the PDOSs of Co and adjacent Pt. There isa large component in d-orbital of Co and d(3z2-r2)-orbital of Pt around the Fermi energy. Thesestates have large difference between P+ and P-.In particular, the peak of d(3z2-r2)-orbital in Pt
gets down across the Fermi energy from P+ to P-. These changes in electronic structure might
contribute to a favor of in-plane easy axis because of a large SOI of Pt. In the presentation, we
will discuss electronic structures like a multi-ferroic material in terms of ferromagnetic andferroelectric properties in the interface.

[1] M. Belmoubarik, et al. Appl. Phys. Lett. 106, 252403 (2015); 109, 173507 (2016).
[2] T. Oda and A. Hosokawa, Phys. Rev. B 72, 224428(2005).
[3] D. Yoshikawa, et al. Appl. Phys. Express 7, 113005 (2014).

Poster-119

Performance information of first-principles codes in K
computer
Kanako Yoshizawa
Research Organization for Information Science and Technology, Kobe 650-0047, Japan*

E-mail: yoshizawa@rist.or.jp

HPCI (High Performance Computing Infrastructure) System including "K computer" [1]provides high performance computing services for scientists and researchers around theworld. User selection and support is conducted by RIST (Research Organization for
Information Science and Technology) in HPCI. As part of the user support, RIST has
installed application software most commonly used in HPCI research projects. The
installation status and usage information of each software are introduced [2].
I have measured the performance of first-principles codes in K computer as port of usage
information. The performance information of Quantum ESPRESSO (PWscf) [3] for
Titanium dioxide (TiO2) is shown in Figure. I show not only the performance information
but also efficient execution methods (e.g. specifying the runtime options) in K computer.

Figure: The performance information of PWscf v6.1 for addition of a hydrogen in rutile
TiO2 (217 atoms per unit cell). The hybrid parallel job running multiple processes and 8
threads.
[1] http://www.hpci-office.jp/folders/english.
[2] http://www.hpci-office.jp/pages/e_appli_software.
[3] http://www.quantum-espresso.org.

First principles study on electronic properties of graphenenanostructures for high current density cathode
Nan Zhao,1 Liangliang Xu,1 Ming-Chieh Lin,1,* and T. C. Leung2,
1

Multidisciplinary Computational Laboratory, Department of Electrical and Biomedical
Engineering, Hanyang University, Seoul 04763, South Korea
2
Department of Physics, National Chung Cheng University, Chia-Yi 62101, Taiwan*

Corresponding author: mclin@hanyang.ac.kr

Graphene is a crystalline allotrope of carbon with two-dimensional properties. Its
carbon atoms are densely packed in a nano-scale hexagonal pattern. Graphene has many
unusual properties. It is about 200 times stronger than the strongest steel. It canefficiently conduct heat and electricity and is nearly transparent. In this work, we study
the electronic properties of graphene using first principles or ab initio calculations basedon density functional theory (DFT) in order to explore its applications in field emission
devices. The electronic structure and density of states of graphene are calculated using
both CPMD and VASP codes for comparison. The work function value is a key parameterand highly desirable for successful graphene applications in the field emisson researcharea. The change of work function due to the lattice deformation of graphene isinvestigated using a supercell including a vacuum layer which is thick enough so that thelayer interaction is negligible. It is found that the work function is very sensitive to thelattice size. As the lattice site increases, the work function increases proportionally.
However, the work function is reduced doubly while the lattice site is reduced. The local
work function of graphene has also been determined and this can be used to predict fieldemission current from Fowler-Nordheim equation more accurately. For realistic
applications, this approach has been used to calculate the work function of carbon
nanoribbons with different widths and terminating edges with and without passivation.
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