International Symposium on Computics:
Quantum Simulation and Design
ISC-QSD2014
Supported by
Grant-in-Aid for Scientific Research on Innovation Area
“Materials Design through Computics: Complex Correlation andNon-equilibrium Dynamics” andComputational Materials Science Initiative (CMSI) in the HPCI Strategic
Program from
the Ministry of Education, Culture, Sports, Science and Technology of Japan

Program and Abstracts

December 1 – December 3, 2014
Koshiba Hall, University of Tokyo
Hongo, Tokyo, Japan

Monday, December 1
9:50 – 10:10 Opening

Chair: Satoshi Watanabe

Opening Address
Atsushi Oshiyama (Symposium Chair)
Shinji Tsuneyuki (Computational Materials Science Initiative: CMSI)

10:10 – 12:05 Oral Session I
10:10
10:45
11:05
11:25
11:45

Chair: Shinji Tsuneyuki

Theoretical and Computational Studies of Quasi Two-Dimensional Materials
Steven G. Louie (invited)
Ab initio GW analysis on low-energy plasmaron states
Kazuma Nakamura
Isotope effect on the band structure of graphene
Takashi Koretsune
Surface as a Foundation to Realizing Designer Materials
Hideaki Kasai
Underscreened Kondo state of collective molecular spin in Mn-Phthalocyanine on Pb(111)Emi Minamitani

Symposium Photo
Lunch

13:30 – 15:05 Oral Session II
13:30

14:05

14:25
14:45

Chair: Kazuhiro Yabana

Ultrafast laser-induced demagnetization of ferromagnetic solids: Identifying the mechanismwith real-time TDDFT
Eberhard Gross (invited)
Application of time-dependent density functional theory to electron emission and scattering
at nano scale
Kazuyuki Watanabe
Photo-Enhancement of Cohesion; Cases of Noble Atoms and Layered Materials
Yoshiyuki Miyamoto
Exact nuclear potential and exact electronic potential in coupled electron-ion dynamics
Yasumitsu Suzuki

Coffee Break

15:30 – 17:55 Oral Session III

Chair: Hiroshi Nakanishi

15:30 Experimental and theoretical study of electron transport through single
π-stacked systems and ionic wires
Manabu Kiguchi (invited)16:05
16:25
16:45
17:05
17:25

First-principles study on tantalum oxide based resistive switching devices
Satoshi Watanabe
Magnetic anisotropy induced by itinerant electrons in Y2Fe14B
Yoshihiro Gohda
Clustering tendency and change in band structure of GaMnAs and InMnAs
Van An Dinh
Robust flat bands in RCo5 (R: rare earth) compounds
Masayuki Ochi
Topological Effects in Tellurium and Selenium
Motoaki Hirayama

18:30

Symposium Dinner (Banquet)

Tuesday, December 2
9:30 – 10:40 Oral Session IV
9:30
10:05

Chair: Mary Inaba

Scientific Simulation on Zetta-Scale computing systems

Kei Hiraki (invited)

Variational Principles and Computation of Linear Response Eigenvalue Problems
with Application to Excited State Calculations

Zhaojun Bai (invited)

Coffee Break

11:00 – 12:35
11:00

11:35

11:55
12:15

Oral Session V

Chair: Zhaojun Bai

Krylov subspace theories and one-hundred-million-atom electronic structure calculations on
the K computer
Takeo Hoshi (invited)
Performance of the Block Jacobi Method for the Symmetric Eigenvalue Problem on the K
computer
Yusaku Yamamoto
Stable and Efficient Linear Scaling First-Principles Molecular Dynamics for 10,000+ atoms
Tsuyoshi Miyazaki
Quantum Monte Carlo simulations of molecular crystal polymorphism on the Ksupercomputer
Kenta Hongo

Lunch

13:40 – 16:40

Poster Session

16:40 – 18:30

Oral Session VI

16:40
17:15

Chair: Eberhard Gross

Water: from deep undercooling to ultrahigh pressure
Roberto Car (invited)
Novel reaction mechanism of Lithium-ion battery electrolyte by DFT free energy calculation
with parallel blue-moon ensemble on K computer
Yoshitaka Tateyama (invited)17:50

18:10

Real-space implementation of the Car-Parrinello molecular dynamics for massively-parallel
computers
Jun-ichi Iwata
Quantum states of positive-muon and proton in materials
Hiroshi Nakanishi

Wednesday, December 3
9:30 – 11:00
9:30

10:05

10:25

Oral Session VII

Chair: Masatoshi Imada“Screened Exchange Dynamical Mean Field Theory” Or How to get rid off the LDA in“LDA+DMFT”
Silke Biermann (invited)
Honeycomb-Lattice Iridates Na2IrO3 under Strong Spin-Orbit Interaction and Electron
Correlation Studied by Ab Initio Scheme
Youhei Yamaji
Effective Coulomb interaction in solids from constrained random-phase approximation
Ersoy Sasioglu (invited)

Coffee Break

11:20 – 12:35
11:20

11:55

12:15

Oral Session VIII

Chair: Yasutami Takada

Adaptation of Dynamical Mean-Field Theory for Nanoscale Systems
Talat S. Rahman (invited)
Mechanism of superconductivity in iron-based superconductors studied by ab-initio
downfolding scheme
Takahiro Misasa
Ab initio calculation of superconducting transition temperature for alkali-doped fullerides
Yusuke Nomura

12:35 – 12:55

ClosingPoster Session
13:40 – 16:40 Tuesday, December 2, 2014

P-01

H. Maeda and D. Takahashi(University of Tsukuba)
Performance Evaluation of Sparse Matrix-Vector Multiplication Using GPU/MIC Cluster

P-02

T. Miyata and K. Nishizawa(Nagoya University)
Multishift QR algorithm with GPU for eigenvalue problems

P-03

Hiori Kino, Takashi Miyake, Koji Hukushima and Masato Okada(National Institute for Materials Science)
Potential energy surface by linear regression, application to Si and SiO2

P-04

A. Nakata, D.R. Bowler, Y. Futamura, T. Sakurai and T. Miyazaki(National Institute for Materials Science)
Efficient optimization of local orbitals and eigenstate calculations in O(N) DFT code
CONQUEST

P-05

Mitsuaki Kawamura, Yoshihiro Gohda, and Shinji Tsuneyuki(The University of Tokyo)
Improved tetrahedron method for the Brillouin-zone integration applicable to DFPT calculations

P-06

Eiji Tsuchida(National Institute of Advanced Industrial Science and Technology)
An algorithm for increasing the stability limit of ab initio molecular dynamics simulations

P-07

Y. Yoshimoto(The University of Tokyo)
Multicanonical simulation combined with first-principles calculation: application to the meltingof iceP-08

T. Kawatsu, K. Ishimura and M. Tachikawa(The University of Tokyo)
Hierarchical parallelization of the ab initio path integral molecular dynamics simulation

P-09

T. Udagawa, T. Tsuneda and Masanori Tachikawa(Gifu University)
Development of new Colle-Salvetti type electron-nucleus correlation functional in MC_DFT

P-10

Shigeru Iwase, and Tomoya Ono(Osaka University)
Efficient treatment of the Green’s function for first-principles transport calculation

P-11

T. Ohgoe and M. Imada(The University of Tokyo)
Multi-variable vartiational Monte Carlo method for electron-phonon coupled systems

P-12

S.A. Sato and K. Yabana(University of Tsukuba)
Ab-initio simulation for initial process of ultrafast laser-processing

P-13

Pham Thi Nu and Kaoru Ohno
(Yokohama National University)
Adiabatic and non-adiabatic molecular dynamics in time-dependent density functional theory

P-14

Kaoru Ohno, Shota Ono, Swastibrata Bhattacharyya, Tomoyuki Horikiri, and Hideo Kosaka(Yokohama National University)
Development of a time-dependent T-matrix theory

P-15

Z. Futera, T. Watanabe, Y.Einaga and Y. Tateyama(Keio University)
Semiconductor-water interfaces investigated by first principle-calculations on boron-doped
diamondP-16

Ryo Kishida, Adhitya G. Saputro, Nakanishi Hiroshi, Wilson Agerico Diño and Hideaki Kasai(Osaka University)
Reaction mechanism of dopachrome conversion, a precursor reaction of melanin biosynthesis:
implications for effects of pH and metal ions

P-17

K. Akagi(Tohoku University)
Water rings at solid-liquid interfaces

P-18

N. Tsuji(The University of Tokyo)
Nonequilibrium dynamical cluster approximation: non-local correlation and real-time dynamics

P-19

Y. Murakami, P. Werner, N. Tsuji and H. Aoki
(The University of Tokyo)
Non-equilibrium DMFT study of thermalization in an electron-phonon system

P-20

Y. Yamada, Y. Yamaji, and M. Imada(The University of Tokyo)
Nonequilibrium dynamics of dissipative excitons in carbon nanotubes

P-21

I. Katayama, K. Maekawa, K. Sat, Y. Minami, K. Yanagi, M. Kitajima and J. Takeda(Yokohama National University)
Fermi Energy Dependence of High-Frequency Coherent Phonons in Metallic Carbon Nanotubes

P-22

Y. Minami, K. Araki, T. D. Dao, T. Nagao, J. Takeda, M. Kitajima, and I. Katayama(Yokohama National University)
Nonlinear Dynamics of Electrons on Dirac-Like Bandin Semi-Metal Bismuth Induced by an THz Electric Pulse

P-23

W. Oba, I. Katayama, Y. Minami, T. Saiki and J. Takeda(Yokohama National University)
Single-shot visualization of ultrafast amorphization in chalcogenide alloy thin films

P-24

Y. Kanematsu, T. Mashiko and M. Tachikawa(Yokohama-City University)
Quantum or thermal fluctuation on molecules in solution

P-25

Masato Oda(Wakayama University)
Electronic structure of a Cerasome Model

P-26

Y. Takano, A. Kusaka, H. Nakamura(Osaka University)
Computational analysis of the molecular interactions in secondary structures of proteins

P-27

Ayori Mitsutake and Hiroshi Takano(Keio University)
Dynamics of 10-Residue Peptide, Chignolin, Studied by Relaxation Mode Analysis

P-28

R. Sato, H. N. Kitoh, T. Kawatsu, K. Yura, K. Ando, T. Yamato(University of Nagoya)
Theoretical Study of the electron transfer reaction by DNA photolyase

P-29

Keitaro Sodeyama, Yuki Yamada, Atsuo Yamada, and Yoshitaka Tateyama(Kyoto University)
Sacrificial anion reduction mechanism for electrochemical stability improvement in highly
concentrated Li-salt electrolyte

P-30

J. Haruyama, K. Sodeyama, K. Takada* and Y. Tateyama(National Institute for Materials Science)
DFT+U investigation of oxide cathode/sulfide electrolyte interface for all-solid-state Li-ion
batteries

P-31

Y. Ootani, K. Sodeyama, L. Han, and Y. Tateyama(National Institute for Materials Science)
Ru Dye–Organic Dye Interaction on TiO2 in Co-Sensitized Dye-Sensitized Solar Cell:
DFT investigation

P-32

L. Szabova, V. Matolin, S. Fabris and Y. Tateyama(National Institute for Materials Science)
Water adsorption and dissociation at metal-supported ceria thin films:
Thickness and interface-proximity effects studied with DFT+U calculations

P-33

S. Hagiwara, C. Hu and K. Watanabe(Tokyo University of Science)Two-component density functional theory of positron state at lithium adsorbed Al(100) surface

P-34

J.Lin, T.Yamasaki and M.Saito(International Center for Materials Nanoarchitectonics)
First-principles study of spin-polarized positron lifetimes in ferromagnets

P-35

Y. Kita, T. Oyamada, and M. Tachikawa(Yokohama City University)
First-princile calculations of positron-attached polyatomic molecules

P-36 T. Ono(University of Tsukuba)
DFT calculations for oxidation of SiC
P-37

Y. Tatetsu, S. Tsuneyuki and Y. Gohda(The University of Tokyo)
Theoretical analysis of Fe/Cu(001) ultrathin films by density functional theory

P-38

K. Sawada, J. -I. Iwata and A. Oshiyama(The University of Tokyo)
First-Principles Calculations on Electronic and Magnetic Properties in Nanofacet on SiC(0001)
Surface

P-39

Christopher Kirkham and Tomoya Ono(Osaka University)
Effect of SiC stacking on the electronic properties of the SiC/SiO2 interface

P-40

S. Arapan, D. Bowler and T. Miyazaki(National Institute for Materials Science)
The role of surface reconstruction in determining the growth path of the {105} facet of a Ge hut

P-41

Miho Nishida, Fumiyuli Ishii, Hiroki Kotaka and Mineo Saito(Kanazawa University)
First-principles study of Rashba effect in artificial superlattice (LaAlO3)n/(SrTiO3)nP-42

H. Kotaka , F. Ishii, and M. Saito(Kanazawa University)
Surface states of Bi (001) multi-layer nano film: spin distribution in the real space andmomentum space

P-43

M. Rahaman , S. Watanabe and J. Iwata(The University of Tokyo)
Stacking-faults and anti-phase boundary energies in Ni3X (X = Si, Ga, Ge) alloys: An ab initio
study

P-44

S. Nakamura, Y. Ando, E. Minamitani, R. Shimizu, K. Iwaya, T. Ohsawa,T. Hitosugi,
S. Watanabe(The University of Tokyo)
Ab-initio calculation of structure and electronic properties of a La0.75Ca0.25MnO3 surface

P-45

T. Kato, H. Kotaka and F. Ishii(Kanazawa University)
First-principles study of strain-induced topological phase transitions in bismuth chalcogenides

P-46

E.F. Arguelles, S. Amino, S. Aspera, H. Nakanishi and H. Kasai(Osaka University)
Surface magnetism induced by interstitial impurities in α-PbO

P-47

K. Shimizu, W.A. Diño and H. Kasai(Osaka University)
Rotational Effects on the Dissociative Adsorption and Abstraction Dynamics of O2/Al(111)P-48

Moh Adhib Ulil Absor, Fumiyuki Ishii, Hiroki Kotaka, and Mineo Saito(Kanazawa University)
Spin-orbit coupling on wurtzite ZnO (1010) surface: first-principles density functional study

P-49

R. Akashi, M. Ochi, S. Bordács, R. Suzuki, R. Arita, Y. Tokura, and Y. Iwasa(The University of Tokyo)
Two-dimensional Valley Electrons and Excitons in 3R MoS2 Multilayers

P-50

R. Akashi and R. Arita(The University of Tokyo)
Hopping Selection Rule of Electrons in Stacked Multilayers and Emergent Flat Band Dispersion

P-51

Yoshitaka Fujimoto and Susumu Saito(Tokyo Institute of Technology)
Electronic Structures and Stabilities of Defects and Impurities in Hexagonal Boron-Nitride
Atomistic Layers

P-52

Sholihun and Mineo Saito(Kanazawa University)
First-principles Calculation of the Free Energy of Silicon Monovacancy

P-53

J. Yamauchi and N. Matsushima(Keio University)
Relaxation effect of X-ray photoelectron spectroscopy for defects in semiconductors:
a first-principles study

P-54

Kanako Yoshizawa, Yoshiki Iwazaki, Yoshihiro Gohda, and Shinji Tsuneyuki(The University of Tokyo)
Charge states of impurity hydrogen in rutile oxide semiconductors MO2 (M=Si, Ge, Sn, Pb, Ti,
Zr, Hf)P-55

M. Alaydrus, M. Sakaue and H. Kasai(Osaka University)
A DFT+U study on oxygen ion migration in strained Sm-doped ceria

P-56

T. Tsumuraya , H. Seo, R. Kato and T. Miyazaki(RIKEN)First-principles study of hydrogen-bonded molecular conductor, κ-H3(Cat-EDT-TTF/ST)2

P-57

Y. Kawashiri, D. Hirai, K. Sasaoka, A. Tawara, and S Watanabe(The University of Tokyo)
Ab-initio calculation for AC transport properties of single molecule bridging between metallic
electrodes

P-58 Teppei Kato, Shinji Usui and Takahiro Yamamoto(Tokyo University of Science)
Thermoelectric Property of Carbon Nanotube Buckypaper
P-59

K.Takashima, T,Yamamoto(Tokyo University of Science)
Quantum Transport Simulation of Edge-Disordered Graphene Nanoribbons

P-60

S. Konabe and S. Okada(University of Tsukuba)
Exciton many-body physics in carbon nanotubes

P-61

A. Yamanaka and S. Okada(University of Tsukuba)
Electronic Properties of Graphene under an Electric Field

P-62

M. Maruyama and S. Okada(University of Tsukuba)
Electronic Structures of Two-dimensional sp2 Carbon Networks of Fused Pentagon Trimers

P-63

K. Uchida, J.-I. Iwata and A. Oshiyama(The University of Tokyo)
Atomic and Electronic Structure Calculations for Twisted Bilayer of h-BN Sheets

P-64

Y. Sakai and A. Oshiyama(The University of Tokyo)
Electronic properties and stacking geometries of bilayer silicone

P-65

T. Tadano and S. Tsuneyuki(The University of Tokyo)
First-principles calculation of high-temperature phonon: Applications to cubic SrTiO3

P-66 M. Geshi(Osaka University)
First-principles calculation of elastic constants for metallic hydrides under high-pressure
P-67

T. Nishimoto, T. Tadano, Y. Gohda, and S. Tsuneyuki(The University of Tokyo)
Development of a first-principles model with long-range interactions for ferroelectrics

P-68

F. Ishii, and H. Kotaka, T. Ohnishi, M. Nishida, M. Saito(Kanazawa University)
Ferroelectric tuning of spin-orbit field in ATiO3(A=Sr,Ba, and Pb)

P-69

D. Hirai, S. Tsuneyuki, and Y. Gohda(The University of Tokyo)
Theoretical Analysis of Magnetic Properties of ε-Fe2O3

P-70

M. Callsen, V. Caciuc, N. Atodiresei, N. Kiselev and S. Blügel(National Institute for Materials Science)
Magnetic hardening induced by nonmagnetic organic molecules

P-71

A. Masago, T. Fukushima, K. Sato and H. Katayama-Yoshida(Osaka University)
Circular polarization in Eu, Mg, and O codoped GaN

P-72

T. Domon, Y. Sugimura, K. Kanazawa, R. Akiyama, S. Kuroda(University of Tsukuba)
Interaction between different kinds of transition-metal elements in quaternary magnetic
semiconductors

P-73 M.-T. Suzuki(RIKEN)First-principles study of multipole ordered states
P-74

W. Sano, T. Koretsune, and R. Arita(The University of Tokyo)
Crystal orientation dependence of the carrier type in IrO2: A first-principles study

P-75

T. Fukushima, H. Katayama-Yoshida, K. Sato, G. Bihlmayer, P.Mavropoulos, D. S. G. Bauer,
R. Zeller and P. H. Dederichs(Osaka University)
First-principles calculation of Hubbard U parameter for gap states in dilute magnetic
semiconductors

P-76

Kazuma Nakamura, Shiro Sakai, Yoshiro Nohara, Yoshihide Yoshimoto(Kyushu Institute of Technology)
Ab initio derivation of low-energy effective model based on constrained many-body perturbation
theoryP-77

Hiroaki Matsui and Hitsohi Tabata(The University of Tokyo)
Material designs of plasmonic nanomaterials on oxides

P-78

K. Miwa, H. Imada, M. Sakaue, H. Kasai and Y. Kim(RIKEN)
Quantum interference between the dynamics of molecular exciton and interface plasmons inscanning tunneling microscope-induced light emission

P-79

M.Shinohara, Y. Yoshida, N. Maruno, Y. Taniguchi, Y. Yoshida, K. Ito, Y. Nakano,Y. Matsuda and H. Fujiyama(Nagasaki University)
Interaction between L-alanine and plasma generated in hydrogen peroxide water

P-80

R. Akiyama, K. Fujisawa, T. Yamaguch, M. Nakatake, A. Kimura and S. Kuroda(University of Tsukuba)
Topological surface state in topological crystalline insulator SnTe thin films

P-81

Shota Ono, Kousei Tanikawa, Riichi Kuwahara, and Kaoru Ohno
(Yokohama National Univ)
End-cap geometry dependence of power conversion efficiency of solar cells based on
capped-carbon nanotubes

P-82

K. Sato, D. Deguchi, T. Kotani, T. Kakeshita and H. Katayama-Yoshida(Osaka University)
Computational design of chalcogenide- and pnictogenidebased photovoltaic solar cell materials

P-83

K. Shirai, K. Sakuma, and N. Uemura(Osaka University)
Survey of high Tc materials in hard semiconducting boron crystals

P-84

R. Akashi and R. Arita(The University of Tokyo)
Density Functional Theory for Plasmon-Assisted Superconductivity

P-85

Masahiro Sakurai and Yasutami Takada(The University of Tokyo)
Superconductivity in Pseudoferroelectric Crystals: Case of n-doped SrTiO3

P-86

T. Koretsune, R. Akashi, S. Sato, H. Isobe and R. Arita(RIKEN)
Possible superconductivity in naphthalene-based organic molecular crystal

P-87

Motoharu Kitatani, Naoto Tsuji, and Hideo Aoki
(The University of Tokyo)
DMFT+FLEX approach to unconventional superconductivity

P-88

S. Kitamura, N. Tsuji and H. Aoki
(The University of Tokyo)
A density functional design of an interaction-driven topological insulator in cold atoms on an
optical lattice

Theoretical and Computational Studies of Quasi Two-Dimensional Materials
Steven G. Louie
University of California at Berkeley and Lawrence Berkeley National Laboratory, Berkeley,
California 94720 U.S.A.
Experimental and theoretical studies of atomically thin quasi two-dimensional
materials (typically related to some parent van der Waals layered crystals) and theirnanostructures have revealed that these systems can exhibit highly unusual behaviors. In
this talk, we discuss some theoretical studies of the electronic, transport and optical properties
of such systems. We present results on graphene and graphene nanostructures as well asother quasi 2D systems such as monolayer or few-layer transition metal dichalcogenides (e.g.,
MoS2, MoSe2, WS2, and WSe2) and metal monochalcogenides (such as GaSe). Owing totheir reduced dimensionality, these systems present opportunities for unusual manifestation ofconcepts/phenomena that may not be so prominent or have not been seen in bulk materials.
Symmetry and many-body interaction effects often play a critical role in shaping qualitatively
and quantitatively their properties. Several novel quantum phenomena are discussed,
exploring their physical origin and comparing theoretical predictions with experimental data.

Ab initio GW analysis on low-energy plasmaron states
Kazuma Nakamura1, Yoshiro Nohara2, Shiro Sakai3, Yoshihide Yoshimoto4
E-mail: kazuma@mns.kyutech.ac.jp
12

Quantum Physics Section, Kyushu Institute of Technology, Japan

Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
3
4Center for Emergent Matter Science, RIKEN, Japan

Department of Information Science, University of Tokyo, Japan

We present a GW study for low-energy plasmaron states in organic and transition-metal compounds. In thesematerials, bands around the Fermi level tend to be isolated from other bands and the former bandwidth iscomparable to local electronic-interaction strengths. Thus, their electronic properties are often discussed in termsof electronic correlation effects. On the other hand, these materials exhibit very low-energy plasmon excitationsof the order of 1 eV, due to the isolated-band structure. In fact, the reflectance and electronic-energy-loss
spectroscopy observe the plasmon excitation at about 1.5 eV for SrVO3 [1] and 1.0 eV for (TMTSF)2PF6 [2,3].
The electron-plasmon coupling is known to generate a plasmaron state [4] being a combined state of electron
and plasmon, and the emergence of this state in the low-energy region will affect the electronic properties.
The purpose of our work is to study these low-energy plasmaron states in real materials from first principles.
We consider two materials, SrVO3 and (TMTSF)2PF6, and calculate ab initio GW spectral functions [5]including the self-energy effects coming from the electron-plasmon scattering, where we identify the relevant
low-energy plasmons through a calculation of the electron-energy-loss function. To ensure the quantitative
accuracy of the plasmaron state, we develop massive parallelized GW code and perform the calculation with avery dense k-point sampling such as 15x15x15. We show that these plasmon excitations modify the original
band structure and transfer a spectral intensity to the plasmaron state. The resulting spectral density of statesshows a reasonable agreement with photoemission spectra. By comparing the theoretical spectral function andthe angle-resolved photo-emission spectra [6,7], we also discuss the origin of the observed incoherent spectral
weight below the main coherent one.

[1] H. Makino et al., Phys. Rev. B 58, 4384 (1998).
[2] C. S. Jacobsen, D. B. Tanner, and K. Bechgaard, Phys. Rev. Lett. 46 1142 (1981)[3] Martin Dressel, ISRN Condensed Matter Physics, 2012 732973 (2012).
[4] B. I. Lundqvist, Phys. Kondens. Mater. 6, 193 (1967); D. C. Langreth, Phys. Rev. B 1, 471 (1970).
[5] K. Nakamura, S. Sakai, R. Arita, and K. Kuroki, Phys. Rev. B 88, 125128 (2013)[6] S. Aizaki et al., Phys. Rev. Lett. 109, 056401 (2012)[7] K. Koizumi, et. al., J.Phys. Soc. Jpn 82, 025004 (2013).

Isotope effect on the band structure of graphene
Takashi Koretsune* and Susumu Saito***RIKEN Center for Emergent Matter Science (CEMS), Japan
E-mail: takashi.koretsune@riken.jp** Department of Physics, Tokyo Institute of Technology, JapanFor the practical use of graphene, it is of great importance to control its band structure and open the bandgap. There are many suggestions to modify the band structure of graphene such as the adsorption ofadatoms on graphene, periodic structure engineering, graphene nanoribbons, and the strain effect. In
addition to these structure modifications, it has been confirmed that the electron-phonon couplings canaffect the band structure in crystalline carbon material, i.e., diamond[1-3]. In the case of graphene, it ispredicted that the Fermi velocity of graphene is reduced due to the electron-phonon couplings using
first-principles calculations[4]. Thus, we discuss the possibility of band structure engineering ingraphene using electron-phonon couplings and isotope effect.
First, we consider the band structure difference between pure 12C graphene and pure 13C graphene. On
the basis of density functional theory, we compute the effect of the second order of electron-phonon
couplings using frozen phonon method and the thermal expansion effect using quasi-harmonic
approximation. Interestingly, it is found that there is a slight isotope dependence in the depth of the socalled Dirac point, that is, the work function of graphene, indicating that it is possible to shift the depthof the Dirac point locally without using the gate voltage.
Next, we consider the possibility of band gap opening using isotope effect. Particularly, we calculate thecase of periodic isotope patterning and find that in some cases, the band gap actually opens due toisotope effect.
1. H. Watanabe, C. E. Nebel, and S. Shikata, Science 324, 1425 (2009)
2. F. Giustino, S. G. Louie, and M. L. Cohen, Phys. Rev. Lett. 105, 265501 (2010).
3. H. Watanabe, T. Koretsune, S. Nakashima, S. Saito, and S. Shikata, Phys. Rev. B 88, 205420 (2013).
4. C.-H. Park et al., Phys. Rev. Lett. 99, 086804 (2007).

Surface as a Foundation to Realizing Designer Materials
H. Kasai*,**,***, W. A. Diño*,**, K. Kojima* and Y. Kawahito***** Department of Applied Physics, Osaka University, Japan** Center for Atomic and Molecular Technologies, Osaka University, Japan*** Center for Continuing Professional Development, Osaka University, Japan**** Joining and Welding Research Institute, Osaka University, Japan
E-mail: kasai@dyn.ap.eng.osaka-u.ac.jp
Novel materials and devices that were once considered science fiction materials are becoming a reality.
However, in the process of the continuing progress in Science and Technology, we encounter new
problems and phenomena where conventional techniques and routines no longer apply. In particular is theastonishing development seen in nanotechnology. To meet the ever-increasing demand for better largescale integration, basic components of devices are getting smaller, with the size ranging from thenanometer-scale to atomic-scale level. With this, one can easily realize that quantum effects become more
important. However, it is not an exaggeration if we say that, with further development, there will come atime when the basic material entity now used to build a device would be developed to function as adevice itself. Given these circumstances, there will be high demands and necessities in developing novel
theoretical routines and techniques that could quickly and efficiently find novel materials for synthesisthat would suit our objectives. These necessary theoretical routines and techniques should incorporate
quantum mechanics per se and should not be dependent on experimental results and/or empiricalparameters. With recent developments in computational techniques, coupled with the rapid progress interms of efficiency and computational capability of present computers, first principles-based
COMPUTATIONAL MATERIALS DESIGN (CMDⓇ) is now a reality. Its influence on industrial R&D
is becoming very significant and will increase in succeeding years. It is worth mentioning that there are
already several precedents of patents granted for application based purely on the application of CMDⓇ
techniques and more are expected to follow.
Here, we will present some non-traditional theoretical views developed in our group. We emphasize theunique role played by the surface/interface for providing a special environment for realizing objective
materials, that are not realizable in the bulk and the strategic choice of particular elements as building
blocks, e.g., for Exhaust Gas Purification[1], Memory Devices[2] and Fuel Cell Applications[3,4].
1. H. Kishi, et al., J. Phys.: Condens. Matter 24 (2012) 262001.
2. H. Kishi, et al., Jpn. J. Appl. Phys. 50 (2011) 071101.
3. M.C.S. Escaño, et al., Chem. Phys. Lett. 555 (2013) 125.
4. For further reference, cf., e.g., http://www.dyn.ap.eng.osaka-u.ac.jp/web/publications.html.

Underscreened Kondo state of collective molecular spinin Mn-Phthalocyanine on Pb(111)
E. Minamitani*, Y. Fu**, Q. K. Que***, Y. Kim****, S. Watanabe** Department of Materials Engineering, the University of Tokyo, Japan
E-mail: eminamitani@cello.t.u-tokyo.ac.jp** School of Physics, Huazhong University of Science and Technology, China*** Department of Physics, Tsinghua University, China****Surface and Interface Science Laboratory, RIKEN, Japan
When a magnetic molecule is placed on nonmagnetic metal surface, the interaction between thelocalized spin in molecule and metal conduction electrons causes the Kondo effect. In Mn
phthalocyanine (MnPc) on Pb(111), the change of the Kondo temperature due to the quantum-well state
formation1 and the competition between Kondo effect and the superconductivity2 in Pb substrate has
been observed experimentally, which makes this system intriguing. However, the mechanism and detailof the Kondo state in MnPc/Pb(111) is still controversial1-3.
In this study, by combining the low-temperature scanning tunneling spectroscopy (STS), density
functional theory (DFT), and numerical renormalization group (NRG) calculation, we show that aunique collective S=1 spin state consists of magnetic moments in ligand π orbital and Mn d-orbitals
occurs in MnPc on Pb(111), which causes the spatially extended underscreened Kondo resonance.
The detailed STS observation clarified that the spectral feature of the Kondo resonance is almost thesame between the Mn site and the pyrrole ring. The DFT calculation shows that the ligand π orbital
antiferromagnetically couples to the magnetic moment in Mn atom. The charge transfer to the ligand π
orbital from Pb substrate induces the reduction of the total spin from S=3/2 of gas phase to S=1. The
NRG calculation results reveal that the Kondo effect screens the half of the collective S=1 spin rather
than screening the individual magnetic moments separately, which causes the spatially extended
underscreened Kondo resonance and allows the coexistence of the Kondo effect and antiferromagnetic
interaction between localized spins.
1. Y. Fu et al., Phys. Rev. Lett. 99, 256601 (2007)
2. K. J. Franke, G. Schulze, J. I. Pascual, Science, 332, 940 (2011)
3. D. Jacob, M. Soriano, and J. J. Palacios, Phys. Rev. B 88, 134417 (2013).

Ultrafast laser-induced demagnetization of ferromagnetic
solids: Identifying the mechanism with real-time TDDFT
E.K.U. Gross
Max-Planck-Institute of Microstructure Physics, Halle (Saale), Germany
E-mail: hardy@mpi-halle.mpg.de
In the past 2 decades many experiments have confirmed that the magnetic moment of ferromagnetic
solids can be demagnetized and even reversed with ultrashort laser pulses. Demagnetization times
achieved in this way are orders of magnitude faster than the present-day magnetic-field-based
technology. How this demagnetization happens on the microscopic level is still under debate. To shedlight on the underlying microscopic mechanism, we study the laser-induced demagnetization of Fe, Co
and Ni using real-time non-collinear time-dependent spin density functional theory (TDDFT). Both the
3D bulk materials and multi-layer slabs are investigated. We show [1] that the demagnetization proceeds
in two distinct steps: First, a fraction of the electrons is excited without much change in the total spinpolarization of the system. In a second step, the spin magnetic moment of the remaining localized delectrons decreases through spin-flip transitions. This process is induced by spin-orbit coupling, i.e.
when spin-orbit coupling is switched off, the moment stays constant in time. For pulse lengths of a few
femto-seconds, the whole process of demagnetization happens in less than 50 femto-seconds. Details of
the time-propagation algorithm will be explained and, employing a combination [2] of TDDFT with
Optimal Control Theory, we furthermore demonstrate how the demagnetization process can becontrolled with suitably shaped laser pulses. Finally, comparing the non-collinear LSDA with a novel xc
functional [3] that exerts a non-vanishing local exchange-correlation torque, we assess the influence of
the approximation used for the exchange-correlation functional. While both functionals allow for fully
non-collinear spin-dynamics, the laser-induced demagnetization process turns out to happen largely in acollinear fashion, i.e. only the z-component of the magnetization vector changes in time, while x- and ycomponents remain very small.
1. K. Krieger, J.K. Dewhurst, P. Elliott, S. Sharma, E.K.U. Gross, arXiv:1406.6607 (2014).
2. A. Castro, J. Werschnik, E.K.U. Gross, Phys. Rev. Lett. 109, 153603 (2012).
3. F.G. Eich, E.K.U. Gross, Phys. Rev. Lett. 111, 156401 (2013).

Application of time-dependent density functional theory
to electron emission and scattering at nano scale
K. Watanabe, T. Higuchi, Y. Ueda, K. Tsubonoya and C. Hu
Department of Physics, Tokyo University of Science, Japan
E-mail: kazuyuki@rs.kagu.tus.ac.jp
Time-dependent density functional theory (TDDFT) [1] has become a standard tool for studying theelectronic states of excitations and non-equilibrium processes in many-electron systems. Great
achievements have been made, especially in the derivation of linear response properties such as opticalabsorption spectra [2] and non-adiabatic couplings [3], as well as simulations of real-time nonlinear
electron emission [4] and current [5] under strong lasers. Quite recently, we have successfully applied
the TDDFT to the real-time simulation of electron scattering with nanostructures [6]. In this presentation,
we report the new findings in the study of electron scattering and plasmon excitation upon electronimpact on nanotargets and laser-assisted field emission (LAFE) from silicene nanoribbons (SiNR), after
reviewing our previous results on the nano low-energy electron diffraction (NanoLEED) of carbon
flakes [6] and the LAFE from graphene nanoribbons (GNR) [4].
The LAFE currents from SiNR are found to be much larger than those from GNR for the same laserparameters, even though the work function of SiNR is larger than that of GNR. We further demonstrate
the ultrafast dynamics of emitted electrons most clearly in real space and time, which are driven backand forth by the oscillating laser fields. The emission mechanism looks very different from the abovethreshold photoemission process that has been reported in many studies.
The NanoLEED patterns showing not only the regular images with periodicity but also special
features caused by the local atomic inhomogeneity have been obtained by shooting the nanotargets withelectron wave-packet (WP). Signatures of π and π+σ plasmon excitations upon electron impact ongraphene flakes have also been observed at the same time and found to show dependence on the incident
angle of the WP. We will discuss the new results on the NanoLEED patterns of aperiodic structures, theanalysis of secondary electron emission and transmission electron microscopy of nanotargets.
1. E. Runge and E. K. U. Gross, Phys. Rev. Lett. 52, 997 (1994).
2. K. Yabana and G. F. Bertsch, Phys. Rev. B 54, 4484 (1996).
3. C. Hu, H. Hirai and O. Sugino, J. Chem. Phys. 127, 064103 (2007).
4. D. Utsugi, C. Hu and K. Watanabe, Appl. Phys. Express 5, 5101 (2012).
5. G. Wachter, et al., Phys. Rev. Lett. 113, 087401 (2014).
6. K. Tsubonoya, C. Hu and K. Watanabe, Phys. Rev. B 90, 035416 (2014).

Photo-Enhancement of Cohesion;
Cases of Noble Atoms and Layered Materials
Yoshiyuki Miyamoto*, Hong Zhang**, Takehide Miyazaki* and Angel Rubio†,‡* Nanosystem Research Institute, National Institute of Advanced Science andTechnology (AIST), Japan
E-mail: yoshi-miyamoto@aist.go.jp** College of Physical Science and Technology, Sichuan University, China†
Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany,‡
Universidad del País Vasco, Spain
This presentation shows our theoretical prosal of photo-enhancement of cohesion in noble gases andlayered materials. Our idea stands for London’s mechanisms of the van der Wassls forces, namely
dynamical dipole-dipole attraction. We found that light near the resonance of either electronic or
vibronic excitation can enhace the dipole moment. We have tested two simple systems, the first is a
dimer of helium (He) atoms and the other is bi-layer of hexagonal boron-nitride (hBN).
In case of He dimer, we performed simulation with extreme ultra-voilet light that is very close to He 1s→2p excitation energy. When the polarization vector of the light is parallel to He-He axis, the light
induce oscillation of electron cloud which causes parallel dipole moment on each He atom. Due to aconcerted motion of electrons and nuclei, the He atoms are accerated to shorten their distance. The
estimated photo-induced effective force is over 7 pN[1]. Meanwhile, in case of hBN, we found that
infrared light can induce out-of-plane optical phonon, A2u mode, which produces parallel dipole
moments to attract each layer. Depdenting on the intensity of light, the speed of inter-layer contraction isgoverned. Subsequent electronic excitation was also exmianed under high intensity of light.
The present simulations were performed within the time-dependent density functional theory[2], using
the plane-wave code[3] with alternating scalar potential mimicking optical field that satisfies totalenergy conservation rule[4] within adiavatic exchange correlation functional. All calculations were
performed by using AIST-super cloud generation II. YM acknowledges support from a fund from the
Science of Atomic Layers (SATL), and the Computational Materials Science Initiative (CMSI), runned
by MEXT.
1. Y. Miyamoto, T. Miyazaki, A. Rubio, and H. Zhang, Appl. Phys. Lett. 104, 201107 (2014).
2. E. Runge and E. K. U. Gross, Phys. Rev. Lett. 52, 997 (1984).
3. O. Sugino and Y. Miyamoto, Phys. Rev. B59, 2579 (1999); B66, 089901(E) (2001).
4. Y. Miyamoto and H. Zhang, Phys. Rev. B77, 165123 (2008).

Exact nuclear potential and exact electronic potential
in coupled electron-ion dynamics
Yasumitsu Suzuki*1, Ali Abedi*, Federica Agostini*, Seung Kyu Min*,
Neepa T. Maitra**, Koichi Yamashita***, E. K. U. Gross** Max Planck Institute of Microstructure Physics, Germany
E-mail: ysuzuki@mpi-halle.mpg.de** Department of Physics and Astronomy, Hunter College and the City University of
New York, USA*** Department of Chemical System Engineering, School of Engineering,
The University of Tokyo, Japan
1
Current address: Nanosystem Research Institute, National Institute of Advanced
Industrial Science and Technology, JapanThe coupling between electronic and nuclear motion plays an important role in many fascinating
phenomena in condensed-matter physics and theoretical chemistry. Towards a full ab-initio descriptionof the coupled electron-nuclear dynamics, we present rigorous reformulations of the quantum
mechanical equations of motion for the coupled system of electrons and nuclei which define the exact
time-dependent Schroedinger equation (TDSE) for the nuclear subsystem and the exact TDSE for theelectronic subsystem. The exact nuclear TDSE features a time-dependent potential energy surface(TDPES) for nuclei, and the exact electronic TDSE features a time-dependent potential energy surface
for electrons (e-TDPES). We show the features of these two exact TDPESs which give correct forces on
nuclei and electrons and govern each motion in the coupled dynamics, with the example of nonadiabatic dissociation of LiH and laser-induced electron localization in H2+. Furthermore we show thepossibility that a novel useful mixed quantum-classical dynamics scheme will be developed based onthese exact TDSEs.
1. A. Abedi, N. T. Maitra and E. K. U. Gross, Phys. Rev. Lett., 105, 123002, (2010).
2. A. Abedi, N. T. Maitra and E. K. U. Gross, J. Chem. Phys., 137, 22A530, (2012).
3. A. Abedi, F. Agostini, Y. Suzuki and E. K. U. Gross, Phys. Rev. Lett., 110, 263001, (2013).
4. F. Agostini, A. Abedi, Y. Suzuki and E. K. U. Gross, Mol. Phys., 111, 3625, (2013).
5. Y. Suzuki, A. Abedi, N. T. Maitra, K. Yamashita, and E. K. U. Gross, Phys. Rev. A 89, 040501(R),(2014).
6. F. Agostini, A. Abedi, Y. Suzuki, S. K. Min, N. T. Maitra, and E. K. U. Gross, arXiv:1406.4667.

Experimental and theoretcial study of electron transport
through single π-stacked systems and ionic wires
M. Kiguchi*, S. Fujii*, T. Tada** and S. Watanabe*** Graduate School of Science and Engineering, Tokyo Institute of Technology, Japan
E-mail: kiguti@chem.titech.ac.jp** School of Engineering, The University of Tokyo, Japan
Understdning how electrons are transported through materials at a single molecular level is an important
challennge in material science. Here, we focus on the electron transport in non-covalently bound, πstacked systems and ionic wires. Because it plays a vital role in biological systems and organic
electronics. However, it is hard to study this topic by experimental method, because assembling thearomatic molecules or ions creating between nanogapped electrodes on the single molecular scale isnontrivial. To overcome this difficulty, we utilized the cages molecules, which can precisely assemble
target molecules. In this study, we have investigated the electron transport of the single caged moleculecontaing aromatic molecule or metal ions using experiment and theoretcal calculation [1,2].
The molecules used in this study are π-stacked molecule (1•(4)n) or [3×n] Au(I) ion clusters enclosed
within the coordination cages as shown in Fig. 1A. The conductance values of the single molecularjunctions of 1•(4)2, 2•(4)3, and 3•(4)4 were determined to be 610–4, 410–4, and 2.510–4 G0,
respectively. The conductance (G) of a short molecularjunction scales exponentially with length according toequation: G=AN exp(–βL), here AN is a constant, L ismolecular length, and β is the exponential pre-factor that
depends on the electronic structure of the molecularjunction. The β values for the π-stacked systems and ionicwire were determined to be 0.1 Å–1 and 0.05 Å–1.
The calculations confirm the efficient conductance ofthe π-stacked systems and ionic wires. Figure 1B shows theFig. 1 (A) Molecular strcuture, (B)Calculated transmission curves and(C) LUMO of the π-stacked systems.

calculated transmission curves for the π-stacked systems.
The HOMO-LUMO gap is about 0.3 eV, which is responsible for the efficient conduction. In addition,
the orbital overlap between the neighboring molecules suffices for orbital-delocalization and electrontransport pathways (Fig.1C).
1.

M. Kiguchi, M. Fujita, T. Tada, S. Watanabe et al. , Angew. Chem. Int. Ed., 50, 5708-5711 (2011).

2.

M. Kiguchi, M. Fujita, T. Tada, S. Watanabe et al. , Angew. Chem. Int. Ed. 52, 6202-6205 (2013).

First-principles study on tantalum oxide based
resistive switching devices
S. Watanabe* and B. Xiao*,*** Graduate School of Engineering, The University of Tokyo, Japan
E-mail: watanabe@cello.t.u-tokyo.ac.jp** Present Affiliation: College of Chemistry and Chemical Engineering,
Yantai University, China
Oxide-based resistive switching devices have attracted much attention because of its potential as nextgeneration memory cells. Among them, amorphous-TaOx based devices show superior endurance andswitching performances. Their switching behavior is understood based on the formation/rupture of
conductive filaments (CFs). However, their atomistic structures and microscopic formation/rupture
processes have not been well clarified yet.
In this presentation, firstly we report our results of density functional calculations (performed with
VASP package) on the CFs in Cu/TaOx/Pt and Pt/TaOx/Pt heterostructures. In Cu/TaOx/Pt, we show thatsingle Cu chains in TaOx cannot work as CFs, while Cu nanowires with a diameter of three atoms orlarger can work as CFs.[1] The stability of the Cu nanowires has been checked by ab initio molecular
dynamics. In Pt/TaOx/Pt with x < 2.5, our results suggest that not O vacancy chain but the Ta-Ta
bonding mainly contributes to the CFs.[2]Next, we report our results on the ion migration behaviors in TaOx examined by ab initio molecular
dybamics and nudged elastic band metnod. For oxygen diffusion coefficient in TaOx, we show that itstrongly depends on x.[3] For Cu at grain boundaries in TaOx, our caluclations using surface models in
stead of grain boundaries suggest that the presence of water strongly promotes its diffusion.[4]1. B. Xiao, T. Gu, T. Tada and S. Watanabe, J. Appl. Phys. 115, 034503 (2014).
2. B. Xiao and S. Watanabe, Nanoscale 6, 10169 (2014).
3. B. Xiao and S. Watanabe, Extended abstract of SSDM2014 (September 8-11, 2014, Tsukuba, Japan).
4. B. Xiao and S. Watanabe, in preparation.

Magnetic anisotropy induced by itinerant electrons in Y2 Fe14 B
Y. Gohda1,2 , Z. Torbatian2 , T. Ozaki3 , and S. Tsuneyuki2,3
1 Department of Materials Science and Engineering,Tokyo Institute of Technology, Yokohama, Japan
E-mail: gohda.y.ab@m.titech.ac.jp
2 Department of Physics, The University of Tokyo, Tokyo, Japan
3 ISSP, The University of Tokyo, Kashiwa, Japan

Magnetocrystalline anisotropy plays an important role in exhibiting the coercivity of permanent magnets [1]. Utilizing itinerant d electrons instead of localized 4 f electrons in exhibiting the magnetic anisotropy
is an important new direction both scientifically and technologically. In the latter sense, the developmentof rare-earth-free magnets will be made possible driven by fundamental understanding of the itinerantelectron anisotropy. Since itinerant magnetic states are responsible to direct interactions among magnetic
sites, d states are expected to be sensitive to lattice strain. In this work, we report strain effects on magnetic
properties theoretically studied by first-principles calculations for Y2 Fe14 B, where Y is a prototypical f 0
rare-earth element [2].
First-principles calculations on the basis of density functional theory within the generalized gradient approximations are performed using the OpenMX code [3]. The lattice constants a and c of Y2 Fe14 B[Fig. 1 (a)] are changed from the equilibrium values independently, where we found the uniform compression enhances the perpendicular magnetic anisotropy. To clarify the origin of this enhancement, we developed a method to decompose the magnetic-anisotropy energy into contribution from each atomic site aswell as from couplings among specific atomic orbitals, where the sum rule is satisfied by including off-site
contributions indirectly in the second-order perturbation. As a result, we clarified that the coupling among
(a)

(b)

0.4
0.2
0
−0.2
−0.4

important role in enhancing the anisotropy, where
both the effect of the local density of states shownin Fig. 1 (b) and the matrix elements among atomic
orbitals are essential. Our method enables us to study
the anisotropy at microstructure interfaces [2].

B
Fe

Y

LDOS (states/eV)

3dx2 −y2 and 3dxy orbitals at the Fe j2 site plays anup

dx2-y2

†＊

down

dxy

0.4
0.2
0
−0.2
−0.4

＊
−4

−2

†

0

2

Energy (eV)[1] S. Hirosawa et al., J. Appl. Phys. 59, 873 (1986).

Figure 1: (a) Crystal structure and spin-density distri[2] Z. Torbatian, T. Ozaki, S. Tsuneyuki, and Y. bution of Y Fe B. (b) Local density of states (LDOS)
2 14
Gohda, Appl. Phys. Lett. 104, 242403 (2014).
projected onto two 3d components of the Fe j2 site with
[3] T. Ozaki and H. Kino, Phys. Rev. B. 72, 045121(2005); http://www.openmx-square.org/(solid lines) and without (shades) compression. Pairs of† and * indicates anisotropy coupling, respectively.

Clustering tendency and change in band structure of
GaMnAs and InMnAs
V. A. Dinh1*, K. Sato1, H. Katayama-Yoshida2 and T. Kakeshita1
1Graduate School of Engineering, Osaka University, Japan*E-mail: divan@mat.eng.osaka-u.ac.jp
2
Graduate School of Engineering Science, Osaka University, Japan
Ferromagnetism (FM) in GaMnAs has been known to be induced by the p-d
exchange interaction of the valence holes and localized d-electrons of Mn atoms[1], andthe Zener p-d exchange interaction model has been widely accepted as the dominate
mechanism inducing FM in GaMnAs[2]. Following this model, the d-orbitals of Mn
hybridize the p-orbitals of As and form an Mn-induced impurity band (IB) that merges
with the valence band (VB) to expand VB towards the bandgap, and the Fermi level(EF) lies in the merged VB. Recently, besides many experimental works support thismodel, several experiments have reported that EF may locate in the separated d-band
inside the bandgap[3], which suggests that the Zener p-d exchange mechanism may not
be the dominant mechanism inducing FM. The above-mentioned confliction is still an
open question and needed to be solved. The fact that the separation of IB from VB is
not found in electronic structure obtained by previous theoretical studies, therefore; it isnecessary to employ a more reasonable method to deal with this problem.
The present study shows that the long-standing question about the origin of FM in
GaMnAs (InMnAs) can be solved by using the hybrid functional method HSE06
implemented in VASP. The most preferable configurations of Mn at various
concentrations were obtained by a full optimization calculation. Band structure anddecomposed band charge density were calculated. The clustering tendency of Mn andthe change in band structure depending on the Mn concentration in clusters were
explored. Our results show an overlap of IB and VB at the dilute concentrations of Mn,
which suggests a possibility of the p-d exchange FM. On the contrary, the separation of
IB from VB was found at higher concentrations. This finding implies that the origin of
FM in GaMnAs would change depending on the Mn concentration.
1. T. Dietl et al. Science 287, 1019 (2000).
2. K. Sato et al., Rev. Mod. Phys. 82, 1633 (2010)
3. S. Ohya, K. Tanaka and M. Tanaka, Nature Phys. 7, 342 (2011).

Robust flat bands in RCo5 (R: rare earth) compounds
M. Ochi1,2, R. Arita1,2, M. Matsumoto3, H. Kino3,4, and T. Miyake3,5
1
RIKEN Center for Emergent Matter Science (CEMS), Japan
E-mail: masayuki.ochi@riken.jp
2
JST ERATO Isobe Degenerate π-Integration Project, AIMR, Japan
3
ESICMM, National Institute for Materials Science, Japan
4
MANA, National Institute for Materials Science, Japan
5
Nanosystem Research Institute, RICS, AIST, Japan
RCo5 compounds, in which Co atoms form the Kagome-honeycomb
stacking structure, have been attracting much attention as the magnetic
materials for their large magnetic anisotropy. Recently, YCo5 waspointed out to have peculiar flat bands on the kx=ky=0 line and in the
kz=0 plane (the Γ-A and Γ-K-M-Γ lines, respectively, in Fig. 1) [1].
When the Fermi level crosses the latter flat band by applying thepressure, it was shown that the system experiences the first-order
Lifshitz transition, which drives the isomorphic collapse of crystalline
lattice [1]. Similar flat bands were also found in LaCo5 [1] and SmCo5[2]. However, why such robust flat dispersions appear has not beenFig. 1 YCo5 band structure

understood yet. In this study, we clarified their origins by analyzing the(majority spin).

tight-binding model consisting of Co 3d and 4s orbitals with thenearest-neighbor hoppings. We found that the both
flat

bands

originate

from

the

destructive

interference [3,4]. For the kx=ky=0 flat band, theBloch state is confined in a Kagome plane since
the Kagome-honeycomb hopping amplitudes areexactly canceled (Fig. 2(a)). The kz=0 flat band isrealized by an extension of the Mielke-Tasaki
mechanism [3,4] for the localized eigenstate
shown in Fig. 2(b).

Fig. 2 Schematic pictures of the localized eigenstatesfor (a) the kx=ky=0 and (b) the kz= 0 flat bands.

1. D. Koudela, et al., Phys. Rev. B 77, 024411 (2008).
2. S. Yehia, S. H. Aly, and A. E. Aly, Comput. Mater. Sci. 41, 482 (2008).
3. A. Mielke, J. Phys. A 24, L73 (1991); ibid. 24, 3311 (1991).
4. H. Tasaki, Phys. Rev. Lett. 69, 1608 (1992).

Topological Effects in Tellurium and Selenium
M. Hirayama*, R. Okugawa**, S. Ishibashi*, S. Murakami**,***, and T. Miyake** Nanosystem Research Institute, AIST, Tsukuba 305-8568, Japan
E-mail: m-hirayama@aist.go.jp** Department of Physics, Tokyo Institute of Technology, Ookayama, Meguro-ku,
Tokyo 152-8551, Japan*** TIES, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8551,
Japan
Dirac cones having a singular point in the momentum space have been under intensive investigation
recently. Among various Dirac systems, materials having three-dimensional Dirac nodes without spin
degeneracy (Weyl nodes) are of particular interest because of their topological nature [1]. We study
trigonal Te and Se (Fig. (a)) as the systems having both strong spin-orbit interaction (SOI) and broken
inversion symmetry, which is highly related to the Weyl node.
Our calculation is based on the density function theory. We use a first-principles code QMAS (Quantum
MAterials Simulator) [2] package for the calculation in the local spin density approximation with the
SOI [3], and the full-potential linear muffin-tin orbitals method for the calculation including the GW
self-energy. The conduction bands have a spin splitting similar to the Rashba splitting around the Hpoints, but unlike the Rashba splitting the spin directions are radial, forming a hedgehog spin texture
around the H points (Fig. (b)). In the metallic phase, the spin rotates twice around H on the kz = ±π/c
plane (Fig. (c)), which can be explained by the motion of the Weyl nodes under pressure [4]. We alsofind that trigonal Te shows the Weyl semimetal phase with time-reversal symmetry under pressure [4].
Fig. (a) Structure of trigonal Te
and Se. (b), (c) Fermi surface
and spin texture of Te aroundthe H point at ambient pressure
and under pressure (3.82 GPa),
respectively.
1. S. Murakami, New J. Phys. 9, 356 (2007); (Corrigendum) ibid. 10, 029802 (2008).
2. http://www.qmas.jp/
3. T.Kosugi, T. Miyake, and S. Ishibashi, J. Phys. Soc. Jpn. 80, 074713 (2011).
4. M. Hirayama, R. Okugawa, S. Ishibashi, S. Murakami, and T. Miyake: arXiv 1409.6399.

Scientific Simulation on Zetta-Scale computing systems
Kei Hiraki
Department of Creative Informatics,
Graduate School of Information Science and Technology
the University of Tokyo
abstract
Today we are constructing Exa-scale computing systems for scientific simulation. We
expect several Exa-scale systems before 2020. Our next target should be Zetta-scale
systems that are 1000 times faster than Exa-scale systems. However, there may be
several obstacles to achieve Zetta flops. In this talk, we present feasibility of Zetta flops
system for numerical intensive computations such as scientific simulations.
We

examineprocessor

architecture,

memorybandwidth/computing

speed,

interconnects, power consumption, the size of the system and the cost to build a Zetta
flops system. As a result of these consideration and estimation, we conclude that we
may have Zetta-scale system around 2030, and it is feasible.
In this talk, we also estimate feasibility of Yotta-scale computing but we have strong
doubt to achieve this level of performance using existing technology. This fact may havestrong impact of future research and development of simulations on material science.

Figure 1. Estimation of Zetta-flops realization based on Top500 trend graphVariational Principles and Computation of Linear Response
Eigenvalue Problems with
Application to Excited State Calculations
Zhaojun Bai
University of California, Davis

E-mail: bai@cs.ucdavis.edu

Linear response eigenvalue problems (LREPs) arise from time-dependent density
functional theory in the linear response formalism. LREPs are challenging due to theirunconventional doubly-structured (non-Hermitian) representation. In this talk, we will
first present recent theoretical results on variational principles of LREPs. These results
are the extension of well-known variational principles for Hermitian eigenvalue
problems. Then we will present the application of these principles in the development of
a conjuguate-gradient like method for large-scale LREPs. Numerical results for the
calculations of multiple low-lying excitation energies of molecules will be presented.
This is a joint work with Ren-cang Li, Dario Rocca and Giulia Galli.

Krylov subspace theories and one-hundred-million-atomelectronic structure calculations on the K computer
T. Hoshi and H. Imachi, Tottori University, Japan
E-mail: hoshi@damp.tottori-u.ac.jp
One-hundred-million atom ( 100-nm-scale ) electronic structure calculations were realized on the K
computer. The linear algebraic methodologies are based on the iterative Krylov-subspace algorithms forthe generalized shifted linear equations ((zS-H)x=b), in stead of the conventional generalized eigenvalue equation (Hy=eSy). [1-3] A high parallel efficiency was observed [3,4] (Fig.1(a)). The calculations
were carried out as an order-N calculation code (http://www.elses.jp/) with modeled (tight-binding)systems based on ab initio calculations. The internal eigen-value problem [5] and optimally combined
dense matrix solvers [6] are also important. Such large-scale calculations are crucial for materials withcomplicated nano domains. Several application studies, such as nano-composite carbon solid (Fig.1(b))
and organic materials (Fig.1(c)), are focused on. The numerical algorithms were developped in thecollaboration with T. Sogabe (Aichi Pref. U), T. Miyata, D. Lee, S.-L. Zhang (Nagoya U). [1,2,5] The
authors thank S. Nishino (U Tokyo / Hulinks Inc.) and T. Fujiwara (U Tokyo) [7] for code development
and discussions.

Fig.1 (a) Parallel efficiency (strong scaling) on the K computer for an one-hundred-million atommaterial [4], (b) An sp2-sp3 nano-composite carbon solid [3], (c) Organic materials or conjugatedpolymers; single chain PFO (upper) and bundled PPV (lower)(The length is L≒40nm).
[1] T. Hoshi, et al., JPCM24, 165502 (2012). [2] T. Sogabe, et al., JC231, 5669 (2012). [3] T. Hoshi, etal., JPSJ 82, 023710 (2013). [4] T. Hoshi, et al., JPS-CP1, 016004 (2014). [5] D. Lee, et al., JJIAM30,
625 (2013). [6] H. Imachi, et al., JSIAM meeting, Tokyo, Sep. (2014). [7] S. Nishino, et al., Sol. Stat.
Ion. 225, 22 (2012).; J. Mol. Model. 19, 2363 (2013); PRB90, 024303 (2014).

Performance of the Block Jacobi Method for theSymmetric Eigenvalue Problem on the K computer
S. Kudo* and Y. Yamamoto*** Graduate School of System Informatics, Kobe University, Japan
E-mail: yusaku.yamamoto@uec.ac.jp** Graduate School of Informatics and Engineering,
The University of Electro-Communications, Japan
Eigenvalue problem of a real symmetric matrix, Ax = x, is an important problem that frequently
appears in quantum chemistry and electronic structure calculations. In this talk, we consider the problem
of computing all the eigenvalues and eigenvectors of a medium-size (n ~ 10,000) matrix on a massively
parallel computer. In this situation, the cost of inter-processor communication becomes dominant andthe standard algorithms based on tri-diagonalization do not scale well.
In our study, we focus on the block-Jacobi algorithm, which is a generalization of the well known
Jacobi algorithm for the symmetric eigenvalue problem. It works on a matrix partitioned into small
blocks and tries to diagonalize the matrix by eliminating the off-diagonal blocks by orthogonaltransformations. Although this algorithm requires much more work than the tri-diagonalziation basedalgorithms, it has simpler computational patterns and larger parallel granularity. Thanks to these features,the algorithm is easier to optimize on modern high performance processors. Moreover, it is expected toattain better scalability for medium-size problems because the overhead of inter-processor
communication and synchronization is smaller.
We implemented the block Jacobi method on the K computer and did some optimizations such as
hiding the inter-processor communications and tuning the solver of a 2 by 2 small eigenproblem, whichis the most time cosuming part of the algorithm. According to our numerical experiments, the resulting
program shows good scalability on the K computer and outperforms ScaLAPACK when solving aneigenvalue problem of size 10,000 using up to 10,000 computing nodes.
References
1.

Y. Takahashi, Y. Hirota and Y. Yamamoto: Performance of the block Jacobi method for thesymmetric eigenvalue problem on a modern massively parallel computer, Proceedings of
ALGORITMY 2012, pp. 151-160 (2012).

2.

Y. Yamamoto, Z. Lan and S. Kudo: Convergence analysis of the parallel classical block Jacobi
method for the symmetric eigenvalue problem, to appear in JSIAM Letters.

Stable and Efficient Linear Scaling First-Principles
Molecular Dynamics for 10,000+ atoms
M. Arita*,**, D. R. Bowler*** and T. Miyazaki*,*** National Institute for Materials Science (NIMS), Japan
E-mail: MIYAZAKI.Tsuyoshi@nims.go.jp** Graduate School of Science and Technology, Tokyo University of Science, Japan*** Department of Physics and Astronomy, University College London, U. K.
The recent progress of linear-scaling or O(N) methods in the density functional theory (DFT) isremarkable. [1] We expect that first-principles molecular dynamics (FPMD) simulations based on DFT
can now treat more realistic and complex systems using the O(N) technique. However, very few
examples of O(N) FPMD simulations exist so far and the information for the accuracy or reliability ofthe simulations is very limited.
In this paper, [2] we show that efficient and robust O(N) FPMD simulations are now possible by the
combination of the extended Lagrangian Born-Oppenheimer molecular dynamics method, which wasrecently proposed by Niklasson et al., [3] and the density matrix minimization method as an O(N)technique. Using our linear-scaling DFT code CONQUEST, we investigate the reliable calculation
conditions for the accurate O(N) FPMD and demonstrate that we are now able to do actual and reliableself-consistent FPMD simulation of a very large system containing 32,768 atoms using about 1000
CPUs of K-computer or FX10. Since CONQUEST has almost ideal parallel efficiency even when weuse more than 10,000 CPUs, [4] we can conclude that FPMD simulations on million-atom systems are
now possible.
1.

D. R. Bowler and T. Miyazaki, Rep. Prog. Phys. 75, 036503 (2012).

2.

M. Arita, D. R. Bowler and T. Miyazaki, J. Chem. Theor. Comput., submitted. (arXiv:1409.6085)

3.

A. M. N. Niklasson, Phys. Rev. Lett. 100, 123004 (2008).

4.

M. Arita, S. Arapan, D. R. Bowler and T. Miyazaki, Journal of Advanced Simulation in Science andEngineering, in press.

Quantum Monte Carlo simulations of molecular crystal
polymorphism on the K supercomputer
Kenta Hongo* and Ryo Maezono** School of Inforamtion Science, JAIST, Japan
E-mail: kenta_hongo@mac.com
The prediction of molecular crystal polymorphism is one of the most challenging topics for
current first principles electronic structure calculations.[1] To deal with the problem satisfactorily,
theoretical methods must have sufficient accuracy to reproduce very weak non-covalent interactions. In
addition, their computational costs must be as low as possible to treat larger unit cells with many more
atoms than typical metals or semiconductors. Therefore, a choice of methods should be determined bytheir balance between computational costs and accuracy. Diffusion Monte Carlo (DMC), one of the mostaccurate and practical quantum Monte Carlo (QMC) methods, may be one of the best choice for treating
molecular crystals.[2] Recent advances in massively parallel computers enable QMC to be applicableeven to periodic systems. Our DMC simulations have for the first time described the polymorph
prediction of para-diiodobenzene (p-DIB) molecular crystals successfully.[3]In the present study we have revisited our investigation of the DMC simulaton of p-DIB
molecular crystal polymorphism to see how finite size errors affect the prediction of the polymorphism.
We performed a significantly larger DMC calculation with a 1×3×3 simulation cell and a DFT nodal
surface obtained from the PBE functional on the K supercomputer. We analyized the finite size effects
using available correction schemes. It was found from our DMC simulations that the resulting
polymorph stability is still consistent with experiment, while standard DFT approaches failed. The
present DMC/1×3×3 calculations were largest posssible simply because of memory size limitation,and thier computational costs amounted to 7.9×105 core-hour with 1024 nodes (2048 cores). Although
DMC simulations with the CASINO program have achieved more than 99% parallel efficiency evenusing 6×105 cores on the K computer, the use of a huge number of cores does not necessarlily speed up
the "total" computational time in "practical" DMC simulations. Our presentation will discuss this kind ofcomputational issues as well.
[1]
[2]
[3]

J. Bernstein, Polymorphism in Molecular Crystals, Oxford University Press, New York, USA,
2002.
R.J. Needs, M.D. Towler, N.D. Drummond, P. López Ríos, J. Phys.: Condens. Matter 22, 023201,
2010.
K. Hongo, M.A. Watson, R.S. Sanchez-Carrera, T.Iitaka, and A. Aspuru-Guzik, J. Phys. Chem.
Lett. 133, 164113, (2010).

Water: from deep undercooling to ultrahigh pressure
Roberto Car,
Princeton University, Princeton, New Jersey 08544, USA
The structure and dynamics of water change dramatically with mutated thermodynamic
conditions, from glassy polymorphs, to metastable and stable liquids, all the way tosuperionic ice forms at extreme pressure and temperature. The huge range of time scales
that characterizes these different states of matter cannot be spanned by a uniquesimulation approach, but requires models with different levels of coarse graining, ranging
from continuous random networks and empirical force fields up to ab-initio molecular
dynamics approaches. In this talk I will discuss some of the unique features associated totetrahedral bonding, the hydrogen bond network and its defects, until it collapses at
extreme pressure and temperature conditions. Connections between theory, simulation,and experiment will be stressed throughout.

Novel reaction mechanism of Lithium-ion battery
electrolyte by DFT free energy calculation with parallel
blue-moon ensemble on K computer
Y. Tateyama1,2,3, K. Sodeyama1,2, K. Ushirogata4, Y. Okuno4
1
WPI-MANA, National Institute for Materials Science (NIMS), Japan
2
ESICB, Kyoto University, Japan
3
PRESTO, Japan Science and Technology Agency (JST), Japan
4
FUJIFILM Corporation, Japan
E-mail: TATEYAMA.Yoshitaka@nims.go.jp
Solid electrolyte interphase (SEI) formed through the reductive decomposition of electrolyte molecules
plays a crucial role in the performance and stability of lithium-ion battery (LIB), a key technology fortoday's energy issue. However, even the initial stage of the formation is still difficult to elucidate,because the reductive decomposition involves combination of solvation change, electron transfer, andbond formation/cleavage.

To predict and design the atomistic mechanism, we need to carry out

comprehensive search of the free energy profiles of possible chemical processes (rare events).
To this end, we have developed the parallel blue-moon ensemble sampling code, called "statCPMD",
based on the original CPMD code [1], and optimized it for the K computer. It shows 29% performanceof floating-point operation per second and 71% of SIMD ratio even in the production run level.
We used "statCPMD" to investigate the additive effects on
the reductive decomposition, using a typical electrolyte
system with ethylene carbonate (EC) solvent and vinylene
carbonate (VC) additive. Evaluating the free energy
profiles along several EC or VC decomposition pathways,
we found that the intact VC additive passivates the EC
anion radical, contrary to the conventional scenario that theminor VC additive is sacrificially reduced instead of major
EC solvent. [2] This new concept with the VC passivation
has been confirmed since our proposal.

Fig.:

Free

energyprofileof

VC

passivation of EC anion radical.

1. CPMD, http://www.cpmd.org/, copyright IBM Corp. 1990−2008, copyright MPI für Festkörperforschung
Stuttgart 1997−2001
2. K. Ushirogata, K. Sodeyama, Y. Okuno, and Y. Tateyama, J. Am Chem. Soc. 135, 11967-11974 (2013).

Real-space implementation of the Car-Parrinello
molecular dynamics for massively-parallel computers
J.-I. Iwata*, K. Koizumi**, Y. Shigeta***, S. Furuya****, M. Boero*****, K.
Uchida* and A. Oshiyama** Graduate School of Engineering, The University of Tokyo, Japan
E-mail: iwata@ap.t.u-tokyo.ac.jp** Institute for Molecular Scince, Japan*** Center for Computational Sciences, University of Tsukuba, Japan**** Argo Graphics Inc., Japan***** IPCMS, University of Strasbourg and CNRS and Computer Mesocenter
Equip@Meso, France
Molecular dynamics (MD) simulation is nowadays an fundamental tool to investigate the behaviour of awide class of materials in realistic environments under different thermodynamical conditions. In theseapproaches, interactions among atoms are described quantum-mechanically, generally within thedensity functional theory framework. Benchmarks and applications over the years in a wealth of systems,
ranging from solids and liquids to biomolecules have promoted these techniques to the level of “virtual
experiments” complementing the real experiments in material sciences. A milestone step forwad was
proposed in 1985 by R. Car and M. Parrinello. In this formualtion, the time-consuming step consisting in
the calculation of the electronic struture at each dynamical step is avoided by extending the MD
Lagrangean to include a fictitious Newtonian motion for the wave functions [1]. Yet, the Car-Parrinello
MD (CPMD) is still computationally expensive for systems including more than a thousand of atoms.
In this presentation, we propose an enhancement in the performance of the CPMD method based on a
new implementation scheme resorting on a real-space approach. Namely, the DFT part of the CPMD isreformulated in terms of our real-space finite-difference pseudopotential method (RSDFT) [2], showing
how large-size systems can become accessible. Contrary to standard plane-wave (PW) methods, RSDFT
does not require any Fast Fourier Transformation in Hamiltonian operations, thus being highly suitable
for massively-parallel architectures. The RSDFT has a remarkable efficiency on the K-computer up totens-of-thousand compute nodes [3]. Specifically, we achieved a speed lower than 10 s for one MD stepfor a few thousands of atoms with a fine grid corrresponding to a cut-off of 100 Ry in PW approaches.
1. R. Car and M. Parrinello, Phys. Rev. Lett. 55, 2471 (1985).
2. J.-I. Iwata et al., J. Comp. Phys. 229, 2339 (2010).
3. Y. Hasegawa et al., Int. J. High Perform. Comp. Appl. 28, 335 (2014).

Quantum states of positive-muon and proton in materials
H. Nakanishi*, H. Kasai*and***Division of Precision Science & Technology and Applied Physics,
Graduate School of Engineering, Osaka University, Japan
E-mail: hiro@dyn.ap.eng.osaka-u.ac.jp** Center for Atomic and Molecular Technologies, Osaka University, Japan
We have been developing the quantum simulation codes, NANIWA Series, for the small mass atom
nuclei and positive muon on solid surfaces, in subsurfaces, interfaces and bulk crystals1-6. In the case ofsmall mass atoms like hydrogen atoms, we have to treat their nuclei (proton) in a quantum-mechanicalmanner, in addition to electrons. The quantum behaviors of such a nuclei have crucial roles to play in thematerials related to today’s energy technology: fuel cell and lithium-ion rechargeable battery1, and also
various catalytic reactions to produce hydrogen fuel 2,3, not only from their academic interests4,5. In thecase of the hydrogen isotope adsorbed on the metal surface, the numerical results for the absolute valueof vibrational excitaton energies and their isotope ratio show the good agreement with exmerimental
data with an uncertainty of less than 10% without artificial fitting parameters, where the simple
harmonic approximation are not good in the real potential energy surface. We can also reverel thequantum behaviors from the ground state up to the excited states localized in subsurfaces.
In this paper, we have investigated the quantum state of positive muon and proton in the covalent
crystals, diamond-structure silicon (Si), graphene (C), and alpha-quartz (SiO2). In the case of Si, we canreproduce the similar quantum behavior to those in previous study7. And we found the different
behaviors of positive muon on the graphene (C)8 and in the alpha-quartz (SiO2)9 from the previous cases.
In the sympsoium, we will discuss the differnt situation of the covalent crystals from the metal surface,and show the various properties of positive muon and proton in the materials.
1. Y. Kubota, et al., J. Phys. Soc. Jpn. 79 (2010) 014601.
2. K. Nobuhara, et al., Surface Science 507-510 (2002) 82.
3. T. Roman, et al., e-J. Surf. Sci. & Nano. 4 (2006) 619.
4. H. Kasai, et al., Progress in Surface Science 44 (1993) 101.
5. W. A. Diño, et al., Progress in Surface Science 63 (2000) 63.
6. N. Ozawa, et al., J. Phys: Cond. Mat., 19,(2007) 365214.
7. T. Miyake, et al., Phys. Rev. Lett. 81 (1998) 1873.
8. A. D. Pant, et al., JPS Conf. Proc. 2 (2014) 010313.
9. H. Nakanishi, et al., Meson, Spring (2014) 6.

“Screened Exchange Dynamical Mean Field Theory” Or
How to get rid off the LDA in “LDA+DMFT”
Silke Biermann
Centre de Physique Théorique (CPHT), École Polytechnique, Cedex

E-mail: Silke.Biermann@cpht.polytechnique.fr
We review recent efforts of incorporating dynamical screening effects into a dynamicalmean field theory (DMFT)-based description of strongly correlated electron materials [1].
Such effects can stem either from higher energy degrees of freedom that have been
integrated out [2,3] or from nonlocal processes that are effectively backfolded into a local
description by combined GW+DMFT techniques [4,5]. These insights lead to a simple
but efficient scheme, dubbed "Screened exchange dynamical mean field theory" [6],which can be understood as a non-perturbative dynamical generalization of Hedin's
Coulomb-hole-screened-exchange approximation. In particular, it includes non-local
exchange beyond the LDA and dynamical screening beyond standard DMFT techniques.
[1] S. Biermann, J. Phys.: Condens. Matter 26 173202 (2014).
[2] M. Casula et al., Phys. Rev. B. 85, 035115 (2012).
[3] J.M. Tomczak et al., Phys. Rev. B 90 165138 (2014)[4] T. Ayral et al., Phys. Rev. B 87, 125149 (2013);
Phys. Rev. Lett. 109 226401 (2012).
[5] P. Hansmann et al., Phys. Rev. Lett. 110 166401 (2013).
[6] A. van Roekeghem et al., Phys. Rev. Lett. in press. (arXiv:1408.3136);
and to be published.

Honeycomb-Lattice Iridates Na2IrO3 under
Strong Spin-Orbit Interaction and Electron Correlation
Studied by Ab Initio Scheme
Y. Yamaji*, Y. Nomura**, M. Kurita**, R. Arita***, and M. Imada*** Quantum-Phase Electronics Center, The University of Tokyo, Japan
E-mail: yamaji@solis.t.u-tokyo.ac.jp** Department of Applied Physics, The University of Tokyo, Japan*** Center for Emergent Matter Science, RIKEN, Japan
Cooperation and competition between strong electron correlations and spin-orbit couplings have recently
attracted much attention. Iridium oxides offer playgrounds for such an interplay and indeed exhibit
intriguing rich phenomena [1,2]. Especially, a theoretical prediction [1] on the possible realization ofquantum spin liquid state and Majorana fermion state proven by Kitaev [3] as the ground state of an
exactly solvable model now called Kitaev model has inspired extensive studies on honeycomb-latticeiridates A2IrO3 (A= Na or Li ) as a model system to realize the Kitaev spin liquid. However, it was shownthat Na2IrO3 does not show spin liquid properties experimentally but exhibits a zigzag type magnetic
order [4], which has triggered further studies on low energy physics of the honeycomb-lattice iridates.
Here we derive an effective low-energy Hamiltonian of itinerant electrons for iridium oxide Na2IrO3 byusing an ab initio downfolding scheme. The model is then reduced to an effective spin model on ahoneycomb lattice by the strong coupling expansion. We show that the ab initio model contains spin-spin
anisotropic exchange terms in addition to the extensively studied Kitaev and Heisenberg exchangeinteractions, and allows to describe the experimentally observed zigzag magnetic order, interpreted as thestate stabilized by the antiferromagnetic coupling of the ferromagnetic chains [5]. We clarify possible
routes to realize quantum spin liquids from existing Na2IrO3.
1. G. Jackeli and G. Khaliullin, Phys. Rev. Lett. 102, 017205 (2009); J. Chaloupka, G. Jackeli, and G.
Khaliullin, Phys. Rev. Lett. 105, 027204 (2010).
2. X. Wan, A. M. Turner, A. Vishwanath, and S. Y. Savrasov, Phys. Rev. B 83, 205101 (2011).
3. A. Kitaev, Annals Phys. 321, 2 (2006).
4. S. K. Choi, et al., Phys. Rev. Lett. 108, 127204 (2012); F. Ye, et al., Phys. Rev. B 85, 180403 (2012).
5. Y. Yamaji, Y. Nomura, M. Kurita, R. Arita, and M. Imada, Phys. Rev. Lett. 113, 107201 (2014).

Effective Coulomb interaction in solids from constrained
random-phase approximation
E. Sasioglu*, C. Friedrich* and S. Blügel**Peter Grünberg Institut and Institute for Advanced Simulation,
Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
E-mail: e.sasioglu@fz-juelich.deDensity functional theory within the local-density approximation (LDA) is a reliable method for
calculating ground-state properties of solids with weak electronic correlations, i.e., for U/W < 1, where
U is the effective on-site Coulomb interaction between localized electrons (Hubbard U) and W is the
bandwidth. However, the LDA often fails to describe systems with intermediate (U/W ~ 1) and strong(U/W > 1) electron correlations, such as transition-metal oxides, rare earths, Kondo systems, etc.
Properties of these materials are usually calculated with phenomenological many-body Hamiltonians
such as the Hubbard or the Anderson impurity model. However, in these models the Coulomb matrix
elements are typically empirical parameters that are determined such that the employed model
reproduces experimental results of interest. The problem of calculating Hubbard U for solids from firstprinciples has been addressed by several authors and a number of different approaches have been
proposed. Among them, the constrained random-phase approximation (cRPA) has recently become themost popular. The basic idea of the cRPA is to define an effective Coulomb interaction U between thelocalized d (f) electrons by restricting the screening processes to those that are not explicitly treated in
the effective model Hamiltonian [1]. Using Wannier functions within the full-potential linearized
augmented-plane-wave (FLAPW) method [2] we developed a parameter-free realization of the cRPA
method [3] and implemented it into the SPEX code [4]. Employing the cRPA method we havecalculated the Hubbard U parameter for different classes of materials such as transition metals [3], halfmetallic magnets [5], carbon-based systems [6], and surfaces of metals and insulators [7].
[1] F. Aryasetiawan, K. Karlsson, O. Jepsen, and U. Schönberger, Phys. Rev. B 74, 125106 (2006).
[2] www.flapw.de[3] E. Şaşıoğlu, C. Friedrich, and S. Blügel, Phys. Rev. B 83, 121101(R) (2011).
[4] C. Friedrich, S. Blügel, and A. Schindlmayr, Phys. Rev. B 81, 125102 (2010).
[5] E. Şaşıoğlu, I. Galanakis, C. Friedrich, and S. Blügel, Phys. Rev. B 88, 134402 (2013).
[6] T. O. Wehling, E. Şaşıoğlu, et al., Phys. Rev. Lett. 106, 236805 (2011).
[7] E. Şaşıoğlu, C. Friedrich, and S. Blügel, Phys. Rev. Lett. 109, 146401 (2012).

Adaptation of Dynamical Mean-Field Theory for Nanoscale Systems*
V. Turkowski, A. Kabir, and Talat S. Rahman
Department of Physics, University of Central Florida, Orlando, FL 32816, USA
Dynamical Mean-Field Theory (DMFT) has established itself as a reliable and well-controlled
approximation for incorporating electron correlation effects in examinations of the spectral
properties of bulk and two-dimensional systems. In combination with the standard densityfunctional theory (DFT) it has been successfully applied to study characteristics of materials inwhich localized electronic states play an important role. In fact, it may be argued that forextended systems this DMFT+DFT approach is more accurate and intuitive than the traditional
DFT+U approximation, particularly because of its ability to take into account dynamical effects,
such as time-resolved double occupancy of orbitals.
In this talk, after a review of essential concepts some details will be presented of our adaptationof the DFT+DMFT method for examining properties of systems at the nanoscale [1], following
the proposal of Florens [1]. In this reliable inclusion of electron-electron correlation effects,
which take us beyond that afforded by DFT, we employ an approximate Iterative Perturbation
Theory (IPT) impurity solver for computational efficiency. We further apply the method to
examine the size-dependent magnetic properties of iron nanoparticles containing up to 150 atoms.
We show that for the majority of clusters the DFT+DMFT solution provides better agreementwith experimental data than the results obtained from DFT or DFT+U. In particular, it
reproduces the oscillations in magnetic moment with size as observed experimentally. We trace
the differences in the results from these three methods to the dynamical changes in electron
density of states which is itself dependent on nanoparticle size and structure. As an aside, theaudience will also be introduced to our very recent effort [3] in combining DMFT with timedependent density functional theory (TDDFT) to formulate a rigorous method for calculating a
nonadiabatic (frequency-dependent) exchange-correlation (XC) kernel appropriate for accurate
description of both equilibrium and nonequilibrium properties of strongly correlated systems.
The validity of the method will be discussed with application to one-orbital Hubbard model forwhich exact solutions are available and for the multi-orbital perovskite Mott insulator, YTiO3,
for which experimental data and DMFT results exist. Novel features appearing in the excitedstate charge densities will be highlighted.
*Work supported in part by DOE Grant DE-FG02-07ER46354
References:
1. S. Florens, “Nanoscale Dynamical Mean-Field Theory for Molecules and Mesoscopic
Devices in the Strong-Correlation Regime”, Phys. Rev. Lett. 99, 046402 (2007).
2. V. Turkowski, A. Kabir, N. Nayyar and T. S Rahman, “A DFT+ DMFT approach fornanosystems”, J. Phys.: Condens. Matter (Fast Track) 22, 462202 (2010).
3. V. Turkowski and T. S Rahman, “Nonadiabatic exchange-correlation kernel for strongly
correlated materials,” (submitted) arXiv preprint arXiv:1409.7683 (2014).

Mechanism of superconductivity in iron-based
superconductors studied by ab initio downfolding scheme
Takahiro Misawa and Masatoshi Imada
Department of Applied Physics, University of Tokyo, Japan
E-mail: misawa@solis.u-tokyo.ac.jp
In iron-based superconductors, although it is believed that electron correlations and orbital degrees of
freedom play key roles in stabilizing high-temperature superconductivity, their roles are not fully
understood yet. To clarify microscopic mechanism of superconductivity in iron-based superconductors,
it is necessary to evaluate strength of interactions in an ab initio way and it is also necessary to seriously
examine the effects of electronic correlations. To challenge these issues, we employ ab initio
downfolding scheme [1]. In this scheme, we first calculate the global band structures for target materials.
Then, we eliminate high-energy degrees of freedom by using the constrained random-phaseapproximation method and obtain the low-energy effective model. To solve the ab initio low-energy
effective models, we use many-variable variational Monte Carlo method, which properly takes into
account both spatial and dynamical quantum fluctuations. We apply this method to the iron-based
superconductors [3-5]. As a result, we show that the calculated magnetic order was shown to correctly
reproduce the experimental material dependences [3,4]. By extending these normal state studies, weshow that superconductivity emerges in the ab initio model of an electron-doped iron-based
superconductor LaFeAsO in essential agreement with the experimental results [5]. The pairing satisfies
gapped s± symmetry and the specific orbital (X2-Y2) is shown to play a key role in stabilizing thesuperconducting phase as well as the antiferromagnetic phase. Then, we find a one-to-one
correspondence between superconductivity and enhanced uniform charge fluctuations. Similar one-toone correspondence is also found in the Hubbard model [6], which is one of the simplest models forcuprates. Despite many differences between iron-based superconductors and cuprates, our study
suggests that the enhanced uniform charge fluctuations play a key role in stabilizing thesuperconductivity in both materials.
[1] For a review, see T. Miyake and M. Imada. J. Phys. Soc. Jpn. 79, 112001 (2010).
[2] T. Miyake, K. Nakamura, R. Arita, and M. Imada, J. Phys. Soc. Jpn. 79, 044705 (2010).
[3] T. Misawa, K. Nakamura, and M. Imada, J. Phys. Soc. Jpn. 80, 023704 (2011).
[4] T. Misawa, K. Nakamura, and M. Imada, Phys. Rev. Lett. 108, 177007 (2012).
[5] T. Misawa and M. Imada, arXiv:1409.6536.
[6] T. Misawa and M. Imada, Phys. Rev. B 90, 115137 (2014).

Ab initio calculation of superconducting transition
temperature for alkali-doped fullerides
Y. Nomura1, S. Sakai2, K. Nakamura3, M. Capone4 and R. Arita2,51
Department of Applied Physics, University of Tokyo, Japan
E-mail: nomura@moegi.t.u-tokyo.ac.jp
2
Center for Emergent Matter Science, RIKEN, Japan
3
Quantum Physics Section, Kyushu Institute of Technology, Japan
4
CNR-IOM Democritos National Simulation Center and SISSA, Italy
5
JST ERATO Isobe Degenerate π-Integration Project, AIMR, JapanThe recent discovery of the superconductivity in A15 and fcc Cs3C60 under pressure [1] has stimulated arenewed interest in the C60 superconductors such as A3C60 (A = K, Rb, Cs). The existence of the Mottinsulating phase in the vicinity of the superconducting phase indicates a crucial role of electron correlations [1].
The observed low-spin state [1] and the dynamical Jahn-Teller effect [2] in the insulating phase revealed a nontrivial interplay of the electron correlations and electron-phonon interactions. Indeed, it had been proposed thata new type of phonon-mediated superconductivity distinct from the BCS superconductivity emerges near theMott transition by the assistance of the electronic correlations [3].
In the present study, we perform fully ab initio studies for alkali-doped fullerides to elucidate the nature of thesuperconductivity: We first derive, from first principles, effective low-energy models consisting of electronic
one-body terms, Coulomb interactions and the phonon terms, whose parameters reflect the material
dependence from fcc K3C60 to fcc Cs3C60 [4,5]. Then, we solve the derived models by the extended dynamical
mean-field theory [6], which enables us to take into account the dynamics of the phonons and the dynamical
screening effects coming from the long-range Coulomb interactions, on top of the local correlations. The
calculated result reproduces the experimental phase diagram at a quantitative level without employing any
empirical parameters. In particular, the calculation reproduces maximum Tc of ~ 28 K, in good agreement withthe experimental result (35 K). We also confirm that the electron correlations indeed assist the pairing bygenerating preformed pairs.
1.

Y. Takabayashi et al., Science 323, 1585(2009); A. Y. Ganin et al., Nature 466, 221 (2010).

2.

G. Klupp et al., Nature Communications 3, 912 (2012).

3.

M. Capone et al., Science 296, 2364 (2002); M. Capone et al., Rev. Mod. Phys. 81, 943 (2009).

4.

Y. Nomura, K. Nakamura, R. Arita, Phys. Rev. B 85, 155452 (2012)5.

For the method to derive phonon-related parameters, see Y. Nomura et al., Phys. Rev. Lett. 112, 027002(2014).

6.

A. M. Sengupta and A. Georges, Phys. Rev. B 52, 10295 (1995); T. Ayral et al., ibid. 87, 125149 (2013).

P-01

Performance Evaluation of Sparse Matrix-Vector
Multiplication Using GPU/MIC Cluster
H. Maeda* and D. Takahashi** Graduate School of Systems and Information Engineering, University of Tsukuba,JapanE-mail: maeda@hpcs.cs.tsukuba.ac.jp** Faculty of Engineering, Information and Systems, University of Tsukuba, Japan
Sparse matrix-vector multiplication (SpMV) is an important computational kernel for many applications
such as scientific computing. For example, in physics and engineering simulations, accelerating SpMV
is expected to reduce the execution time of an existing application. Algorithms for SpMV [1] areproposed in several studies. However, their effects are largely dependent on the architecture of thecomputer and the nonzero structure of the matrix. Hence, the most appropriate method depends on thematrix and the architecture of the computer.
Recently, an increasing number of computing systems have been equipped with NVIDIA's GPU andIntel's Xeon Phi coprocessor based on the Many Integrated Core (MIC) architecture proposed by Intel in2010. A system equipped with the Xeon Phi coprocessor was ranked first and a system equipped with
K20X, which is NVIDIA's GPU, was ranked second in the TOP500 list in June 2014. Many studies
apply GPU to SpMV, such as GPU aware algorithms and sparse matrix formats, and also several studies
apply MIC to SpMV.
The High Performance Conjugate Gradient (HPCG) benchmark, which uses the conjugate gradient (CG)method, was proposed. HPCG is aimed to overcome the disadvantages of High Performance Linpack(HPL), which is unreliable as a true measure of system performance for a growing collection ofimportant science and engineering applications. Since HPCG contains SpMV, it is considered that
SpMV will increase in importance. For this reason, algorithms for SpMV using the accelerator
effectively on clusters are required. To the best of our knowledge, while previous studies have reported
CPU and GPU implementations of SpMV for a cluster and MIC implementations for a single node,
implementations of SpMV for the MIC cluster have not yet been reported. However, the MIC cluster is
expected to achieve higher performance than CPU and GPU clusters.
Therefore, we implement and evaluate parallel SpMV on a GPU/MIC cluster.
1. M. Lange, G. Gorman, M. Weiland, L. Mitchell, and J. Southern,“Achieving Efficient Strong Scaling
with PETSc Using Hybrid MPI/OpenMP Optimisation,” Proc. ISC 2013, Lecture Notes in Computer
Science, Vol. 7905, pp. 97–108, Springer Berlin Heidelberg (2013).

P-02

Multishift QR algorithm with GPU for
eigenvalue problems
T. Miyata and K. Nishizawa
Graduate School of Engineering, Nagoya University, Japan
E-mail: miyata@na.cse.nagoya-u.ac.jp
In this talk, we consider computing eigenvalues of non-Hermitian matrices using GPU. In the standard
procedure to compute eigenvalues, a non-Hermitian matrix is first reduced to a Hessenberg form by theHouseholder algorithm and then the eigenvalues of the Hessenberg matrix is computed. The first step
can be performed efficiently with GPU [1,2]. Here, we focus on the second step. Our approach is basedon the multishift QR algorithm [3], which is originally proposed in [4] and is improved in [3] on theconvergence property. This algorithm can perform a major part of computations in the form of matrix
multiplications and is therefore suited to high performance architectures. In our approach, GPU is used
for matrix multiplications and CPU multicores are used for the other computations in the algorithm. To
attain higher performance, we need to optimize the block size in matrix multiplications, while keeping
high efficiency of using both GPU and CPU. We show several implementations of the algorithm, andreport results of performance evaluation.
1. J. Muramatsu, T. Fukaya, S.-L. Zhang, K. Kimura, and Y. Yamamoto, Int. J. Netw. Comput., 1 (2011).
2. MAGMA (http://icl.cs.utk.edu/magma/).
3. K. Braman, R. Byers, and R. Mathias, SIAM J. Matrix Anal. Appl. 23 (2006).
4. Z. Bai and J. Demmel, Int. J. High Speed Comput., 1 (1989).

P-03

Potential energy surface by linear regression,
application to Si and SiO2
Hiori Kino*,**, Takashi Miyake**,***, Koji Hukushima****and Masato Okada*******National Institute for Materials Science (NIMS-MANA), Tsukuba, Ibaraki, Japan.
E-mail: kino.hiori@nims.go.jp**ESICMM, National Institute for Materials Science, Tsukuba, Ibaraki, Japan.
***Nanosystem Research Institute, “RICS”, AIST, Tsukuba, Ibaraki Japan.
****Department of Basic Science, Graduate School of Arts and Sciences,
The University of Tokyo, Japan.
*****Graduate School of Frontier Sciences, The University of Tokyo,
Kashiwa, Chiba, JapanThe first-principles theory has achieved great success in materials science. Now it is applied to largescale systems through order(N) algorithm and/or massively parallel computers. However, we need thelarger sizes of the systems and longer simulation time for realistic systems, therefore we still demands
the larger and larger computational resources.
It is apparent that the computational time can be greatly reduced if we have accurate potential energy
surface consistent with the results of the first-principles theory. Many works are recently carried out
along this line, and the techniques of neural-network, Gaussian process regressions, and linear
regression are employed.[1,2,3] We adopt the linear regression method to construct potential energy
surface in this presentation. It is the simplest technique and its main merit is that it doesn’t have the local
minimum problem in producing the classical potential.
The previous work has shown that the linear regression method can successfully reproduce the potential
energy surface of the simple system. We apply it to more complex systems, such as Si and SiO2, which
we consider are good benchmarks to expore the applicability of the linear regression method because of
the complex phase diagrams and because the energy difference among the phases are quite small. We
also comment how to generate sampling points to avoid the simulation in the extrapolating region of themodel potential.
1.

J. Behler and M. Parrinello. Phys Rev. Lett. 98, 146401 (2007).

2.

A.P. Bartók, M.C. Payne ,R. Kondor and G. Csányi, Phys. Rev. Lett. 104, 136403 (2010).

3.

A.Seko, A. Takahashi and I. Tanaka, Phys. Rev. B 90, 024101 (2014).

P-04

Efficient optimization of local orbitals and eigenstatecalculations in O(N) DFT code CONQUEST
A. Nakata*, D.R. Bowler** , Y. Futamura***, T. Sakurai*** and T. Miyazaki**National Institute for Materials Science (NIMS), Japan
E-mail: NAKATA.Ayako @nims.go.jp** Department of Physics & Astronomy, University College London (UCL), U. K.
*** Department of Computer Science, University of Tsukuba, Japan
CONQUEST[1] is a linear-scaling (O(N)) DFT code developed jointly by UCL and NIMS. CONQUEST
achieves O(N) by using the locality of density matrices with the density matrix minimization method.
Local orbitals which are called support functions are used to express the locality of density matrices. We
have introduced multisite support functions[2], which are the linear combinations of pseudo-atomic
orbitals from a target atom and its neighbor atoms. Multisite support functions correspond to local
molecular orbitals so that the number of required support functions can be the minimal. The multisite
support functions are determined by using the localized filter diagonalization (LFD) method [3]. The
double cutoff method and the smoothing method are introduced to improve efficiency and stability.
The accuracy and computational efficiency of the present method are demonstrated by investigating
the energetic and geometrical properties of several systems. Fig. 1 shows the calculated density of statesaround HOMO-LUMO gap of a hydrated DNA system. The present method has succeeded in providing
the band-gap energy with the error less than 0.01 eV from the conventional method while reducing thecomputational time to about 1/10.
We have also employed an efficient projection method to obtain the eigenstates in specific energy
ranges proposed by Sakurai and Sugiura[4] with thesparse matrices constructed by CONQUEST. It
enables us to obtain efficiently band energies andcharge densities in the specific energy ranges. The
results and efficiency of this method has been
compared with those of the conventional exact
diagonalization method in CONQUEST.

Fig. 1. Density of states of hydrated DNA.

1. http://www.order-n.org/
2. A. Nakata, D. R. Bowler, T. Miyazaki, J. Chem. Theory Comput., in press [DOI: 10.1021/ct5004934].
3. M. J. Rayson and P. R. Briddon, Phys. Rev. B, 80, 205104 (2009).
4. T. Sakurai and H. Sugiura, J. Comp. Appl. Math., 159, 119 (2003).

P-05

Improved tetrahedron method for the Brillouin-zone
integration applicable to DFPT calculations
Mitsuaki Kawamura*, Yoshihiro Gohda**, and Shinji Tsuneyuki*,****Department of Physics, The University of Tokyo, Japan
E-mail: kawamura@cms.phys.s.u-tokyo.ac.jp**Department of Material Science and Engineering,Tokyo Institute of Technology, Japan***Institute for Solid State Physics, The University of Tokyo, Japan
Calculations of phonons based on density functional perturbation theory (DFPT) require numerical integrations of
the following form.

∫ d3 kµ( "F −"k ) µ( "k +q −" F )Xk.
"k +q −" kSince "k and Xk are provided only on finite points in the
Brillouin zone, we have to carry out the k point summation
instead of the integration. To accelerate its k convergence,
following two methods have been used.
Figure 1. k convergence of Fröhlich's- The broadening method
Step functions are replaced with smeared functions. The mass enhancement parameter of fcc Li.
drawback of this method is the k-converged values de- The horizontal axis indicates the numberof k points used in calculations of phononpend on broadening widths (see Fig. 1).
frequencies based on DFPT. Dashed lines-The linear tetrahedron method"k and Xk are interpolated lineally in the small tetrahe- indicate results obtained by using thedral regions. Then analytical integration is performed broadening method with different broadseparately in each tetrahedron. The drawback of this ening widths. Solid lines labeled “L-tetra”
method is systematic overestimation (underestimation) and “Our method” indicate results of theof integrals of convex (concave) function because of the linear tetrahedron method and our imlinear interpolation. This overestimation (underestima- proved tetrahedron methods, respectively.
tion) makes the k convergence slow (Fig. 1).
In this work, we improve the tetrahedron method to remedy its systematic error. We construct an optimum linear approximate function which is free from the continuity constraint on boundaries of tetrahedra [1]. Using this method, we perform calculations of Flöhlich's mass enhancement parameter in fcc
lithium based on DFPT. The result clearly shows the advantage of our method: convergence faster thanthe conventional tetrahedron method (Fig. 1).
1. M. Kawamura, Yoshihiro Gohda, and Shinji Tsuneyuki, Phys. Rev. B 89, 094515 (2014).

P-06

An algorithm for increasing the stability limit of ab initio
molecular dynamics simulations
Eiji Tsuchida** Nanosystem Research Institute, National Institute of Advanced Industrial Science andTechnology (AIST), Tsukuba Central 2, Umezono 1-1-1, Ibaraki 305-8568, Japan
E-mail: Eiji.Tsuchida@aist.go.jp
The computational cost of ab initio molecular dynamics (AIMD) is still a serious obstacle, even on asupercomputer. If, however, the goal of the simulation is to obtain low-energy conformations throughsimulated annealing, or to equilibrate the system prior to the production run, the computational cost is
minimized by using the largest possible time step. When the Verlet method is used to integrate theequations of motion, the maximum size of the time step is given by hmax = T/π, where T is the periodof the fastest oscillation in the system. In practice, however, AIMD simulations often break down at~ hmax /2 due to the strong anharmonicity of the interatomic forces.

In this presentation, we show that the stability limit of the Verlet method may be significantly

increased by setting an upper bound on the kinetic energy of each atom with only a small loss of
accuracy. The validity of our approach is demonstrated for molten LiF.
1.

E. Tsuchida, “Stabilization of Ab Initio Molecular Dynamics Simulations at Large Time Steps”,
http://arxiv.org/abs/1409.6849

P-07

Multicanonical simulation combined with first-principles
calculation: application to the melting of ice
Y. Yoshimoto
Graduate School of Information Science and Technology, The University of Tokyo,JapanE-mail: yosimoto@is.s.u-tokyo.ac.jp
First principles calculations based on density functional theory is a powerful method to obtain rather
accurate force field for various atomic systems. However, although its computational cost is rather
economical compared to other first principles methods, the cost is sometimes too heavy to simulate thestatistical properties of systems, such as critical temperatures of phase transitions. To tackle this issue,
the author proposed a a combined method of multicanonical simulations and first principles calculations.
[1,2] In the method, the statistical properties are simulated by multicanonical simulations using lightweight inter-atomic model potentials which is self-consistently determined by first-principles
calculations so that the thermodynamics of the system is kept to a maximum extent, utilizing a property
of multicanonical ensembles.
In this prsentation, the author reports the application of the method on the melting of ice. Water is anubiquitous material and how the thermal property of ice is reproduced is an important issue for firstprinciples simulations of biological systems, electrochemical systems, and so on.
The simulated melting temperatures (Tc) and corresponding latent heats (ΔH) of ice using various
approximations of the density functional are shown in the Table 1. The results suggest that it isimportant to take both the hybrid functional effect and dispersion force effect (DFT-D3[3]) into
account.The simulated O-O pair correlation functions for water phases are also shown in Fig. 1. The
simulated pair correlation functions are rather similar each other when the temperature is adjusted fromthe obtained melting temperature.
Tc

ΔH

PBE

410

13.9

PBE0

373

12.3

B3LYP

337

9.8

B3LYP+DFT-D3

283

6.3

experimental

273

6.01

Table 1: melting temperature (Tc [K])and latent heat (ΔH [kJ/mol]) of ice.

Fig. 1: O-O pair correlation functions
by various functionals. exp.: A. K. Soper,
M. G. Phillips, Chem. Phys.. 107, 47 (1986)

1. Y. Yoshimoto, J. Chem. Phys., 125, 184103 (2006).
2. Y. Yoshimoto, J. Phys. Soc. Jpn., 79, 034602 (2010).
3. S. Grimme, J. Antony, S. Ehrlich and B. Krieg, J. Chem. Phys. 132, 154104 (2010)

P-08

Hierarchical parallelization of the ab initio path integral
molecular dynamics simulation
T. Kawatsu*,**, K. Ishimura*** and M. Tachikawa***Graduate School of Arts and Sciences, The University of Tokyo, Japan**Graduate School of Nanobioscience, Yokohama City University, Japan
E-mail: kawatsu@fukui.kyoto-u.ac.jp***Institute for Molecular Science, National Institutes of Natural Sciences, Japan
The path integral theory is a useful tool for developing computational methods to treat nuclear quantum
effects of light particles like proton. Many of such methods have theoretical structures fitting to theparallel computing. Recently, ab initio quantum chemical codes have well been developed for parallel
computations. The combination of the path integrals andab initio calculations can directly make a hierarchicalparallelized computation with these parallelized axes.
We have developed a path integral molecular dynamics(PIMD) code1 for investigating various hydrogenbonding or hydrogen transferring systems, which code
has called external quantum chemical programs. In
present study, we have improved our parallelized PIMD
code to combine with an ab initio quantum chemicalcode, SMASH,2 which efficiently parallelized with ahybrid interface of MPI and OpenMP. The PIMD code
calls the SMASH as a subroutine and then includes two
hierarchical MPI and an OpenMP parallelized structure.
Benchmark results of the parallelized efficiency for

Figure 1. Efficiency of the parallel
computing for the ab initio path
integral molecular dynamics (PIMD)
simulation of a C60H2 molecule.

the PIMD code is shown in Figure 1. The model system
is a C60 fullerene including a hydrogen molecule inside and expanded with 16 beads (replica of themolecular system) isomorphic ring polymer by the path integral theory. Intramolecular forces arecalculated using B3LYP/STO-3G. The benchmark ran up to 1024 cores of Intel Xeon processors in
PRIMERGY CX400 computer. The parallel efficiency is excellent in this range.
1. K. Suzuki, M. Shiga, and M. Tachikawa, J. Chem. Phys. 129, 144310 (2008)
2. http://smash-qc.sourceforge.net/

P-09

Development of new Colle-Salvetti typeelectron-nucleus correlation functional in MC_DFT
T. Udagawa*, T. Tsuneda** and Masanori Tachikawa**** Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu
University, Japan
E-mail: udagawa@gifu-u.ac.jp** Fuel Cell Nanomaterials Center, University of Yamanashi, Japan*** Quantum Chemistry Division, Graduate School of Science, Yokohama City
University, Japan
Nuclear quantum effect often plays important role in physical phenomena and chemical reactions, suchas phase transition of the hydrogen-bonded crystals, hydrogen/proton transfer reactions, and so on. Oneof the straightforward methods for incorporating nuclear quantum effects is multi-component density
functional theory (MC_DFT) [1]. In the MC_DFT framework, we should evaluate not only electronelectron (ee) correlation effect but also electron-nucleus (en) one. We have recently propose a new
Colle-Salvetti (CS) type en correlation funcational for MC_DFT [2].
en

The CS type en correlated wavefunction "CS can be written as a product of the Kohn-Sham(KS) wavefunction ( "KS ) containing ee correlation and the CS correlation factor for the en one (φen).

[

]

en
"CS
= "KS % 1 # $ en (ri ,rn )
i,n

(1)

!

!" en (r ,r ) = exp #$ 2 r 2 ,-1 # %en (r ) &1 # Z r + 1 Z 2 r 2 # 1 Z 3 r 3 )/0
i n
en
n (
n
'
2 n
6 n +*1
.

(

)

(2),

!where r and r are the position vectors of electrons and nuclei, respectively, r = |r – r |, and Z is the
i

n

i

n

n

nuclear charge of nucleus n. βen corresponds to the amplitude of correlation region and includes the only

!parameter qen. To assess the performance of our ep correlation (epc) functional, we compared the sum of
the DFT energy using the Becke exchange + one-parameter progressive correlation (BOP) functionals
and zero-point vibrational energies with the sum of MC_BOP and epc energies for 18 small systems,
which are composed to both hydrogen and first- and second-row atoms. The mean absolute deviation is
only 2.8 millihartree, which indicates that our epc functional quantitatively evaluates epc. I would like toshow other practical calculations with new electron-deuteron and electron-triton correlation functionals.
1. J. F. Capitani, R. F. Nalweajski, R. G. Parr, J. Chem. Phys. 76, 568 (1982), T. Kreibich, E. K. U.
Gross, Phys. Rev. Lett. 86, 2984 (2001).
2. T. Udagawa, T. Tsuneda, M. Tachikawa, Phys. Rev. A, 89, 052519 (2014).

P-10

Efficient treatment of the Green’s function
for first-principles transport calculation
Shigeru Iwase*, and Tomoya Ono***Graduate School of Engineering, Osaka University, Japan
E-mail: iwase@cp.prec.eng.osaka-u.ac.jp**Center for Computational Sciences, University of Tsukuba, Japan
There is strong demand for large first-principles transport calculations in order to deal with realistic
nanostructures. For this purpose, real-space transport methods such as overbridging boundary-matching(OBM) method[1] are promising because they are highly parallelizable and simple to converge. However,in practice, the transport calculations have been limited to be applied for relatively small systems since it
requires explicit matrix-inversion procedure to obtain Green’s function, which lead very large
computational demand. Therefore, there is room for refinement of the transport calculation method in order
to execute fully atomistic calculation on large systems. In the OBM method, it should be noted that thematrix to be inverted does not include the nonlinear energy dependent term, which is different from thatused in nonequiribrium Green’s function method. The Green’s functions in the OBM method aredetermined by solving shifted linear equations in terms of the energy, which can be efficiently treated by
employing shifted conjugate-orthogonal conjugate-gradient (shifted COCG) method[2].
In the present work, we propose the procedure combining shifted COCG algorithm with OBM method.
To demonstrate the applicability of this procedure, the transport calculation of both small and large systems
are examined. Figure 1 shows the CPU time versus the number of energy sampling points, which indicatesthat the computational cost is greatly reduced by the present method. Figure 2 shows conductance spectrumof a carbon nanotube encapsulating one C60. The calculated transmission spectrum has three dips above thefermi level which corresponds to decoupled t1u states of C60 and act as a scattering center.

Fig. 1. CPU time required to calculate theGreen’s function of Na monowire

Fig. 2. Conductance spectra of the 1C60@(10,10)
as function of the incident energy

1.

Y. Fujimoto and K.Hirose, Phys. Rev. B 67, 195315 (2003).

2.

R. Takayama, T. Hoshi, T. Sogabe, S.-L. Zhang, T. Fujiwara, Phys. Rev. B 73, 165108 (2006).

P-11

Multi-variable vartiational Monte Carlo method forelectron-phonon coupled systems
T. Ohgoe and M. Imada
Graduate School of Engineering, The University of Tokyo, Japan
E-mail: ohgoe@solis.t.u-tokyo.ac.jp
The electron-phonon interaction plays an important role in various phenomena of condensed mattersuch as conventional superconductor, charge density wave, and electric resistivity. Although its roles arewell understood in those phenomena, they have not been fully understood in strongly-correlated
electrons such as high-Tc cuprates. For the study of strongly-correlated electrons, there are several
numerical methods such as exact diagonalization (ED), density-matrix renormalization group (DMRG),
dynamical mean-field theory (DMFT), quantum Monte Carlo (QMC) method, and variational Monte
Carlo (VMC) method. Among them, VMC method takes the advantage of wide applicability because it
does not suffer from the notorious sign problem. In addition, we are able to improve its accuracy
systematically by introducing many variational paramters (multi-variable VMC)[2,3]. However, its
applications have been usually restricted to electronic systems without electron-phonon interactions
because of the absence of an appropriate variational wave function.
In this work, we have developed a multi-variable VMC method for electron-phonon coupled systems.
Our proposed variational wave function consists of three elements: the electronic wave function, thephonon wave function, and an electron-phonon correlation factor. The electron-phonon correlation
factor takes into account the entanglement between electrons and phonons. To check the accuracy of ourvariational wave function, we obtained benchmark results of the one-dimensional Holstein-Hubbard
model. In the benchmarks, we have compared our results with ED and DMRG results and have shown
good agreements. As an application, we have studied the two-dimensional Holstein-Hubbard model. In
one dimension of the same model, the DMRG studies showed the presence of an intermediate metallic
phase between charge-density wave and spin-density wave phases at zero temperature[4]. In contrast,
the DMFT which is exact in infinite dimensions supported its absence[5]. In the case of two dimension,
we obtained results which support the presence of an intermediate phase.
1. S. Sorella, Phys. Rev. B 64, 024512 (2001)
2. D. Tahara and M. Imada, J. Phys. Soc. Japan 77, 114701 (2008)
3. T. Ohgoe and M. Imada, Phys. Rev. B 89, 195139 (2014).
4. Fehske et al., Eur. Phys. Lett. 84, 57001 (2008)
5. J. Bauer and A. Hewson, Phys. Rev. B 81, 235113 (2010)

P-12

Ab-initio simulation for initial processof ultrafast laser-processing
S.A. Sato* and K. Yabana*** Graduate School of Pure and Applied Science, University of Tsukuba, Japan
E-mail: sato@nucl.ph.tsukuba.ac.jp** Center for Computational Science, University of Tsukuba, Japan
We present an ab-initio simulation for initial stage of ultrafast laser-processing in dielectrics where
femtosecond laser pulses induce electronic excitations in the surface of dielectrics within a femtosecond
time scale. In order to understand the mechanism, it is important to understand ultrafast energy transfer
processes from the laser pulse to electrons in the dielectric surface. We have been developing atheoretical and computational method to describe electron dynamics in crystalline solids induced byintensea and ultrashort laser pulses in the first-principles level based on the time-dependent density
functional theory (TDDFT). Combining the TDDFT solver for electron dynamics with the finitedifference time-domain (FDTD) solver for macroscopic electromagnetic fields using multiscale
methodology [1,2], we have for the first time
successfully realized a simulation method todescribe the initial stage of ultrafast laserrocessing in dielectrics.
Figure 1 shows calculated energy transfer from
intense laser pulses of 10 fs time length andseveral intensities to a surface of bulk SiO2 asfunctions of distance from the surface. Comparing
the transferred energy at the surface with thecohesive energy of SiO2, the laser intensity and thefluence at the ablation threshold is estimated to be
2.5x1014 W/cm2 and 1.9 μJ/cm2. This value is inexcellentagreement

with

the

experimental

ablation threshold fluence, 2 μJ/cm2 [3].

Fig. 1. Absorbed energies of bulk SiO2 asfunctions of distance from the irradiatedsurface. The cohesive energy of SiO2 is also
shown as a horizontal line.

1.

K. Yabana, et al, Phys. Rev. B 85, 045134 (2012).

2.

S.A. Sato and K. Yabana, to be published in Journal of Advanced Simulation in Science andEngineering.

3.

M. Lenzner, et al, Phys. Rev. Lett. 80, 4076 (1998).

P-13
Adiabatic and non-adiabatic molecular dynamics intime-dependent density functional theory
Pham Thi Nu and Ohno Kaoru
Department of Physics, Graduate School of Engineering,
Yokohama National University, Japan
E-mail: pham-thinu-rf@ynu.jp
In the Born-Oppenheimer approximation, often called the adiabatic approximation, the nuclear kinetic energy isignored and the nuclear positions are considered merely as parameters to solve the electronic Schrodinger
equation. This approximation, however, breaks down when nucleus has significant velocity [1]. Then the nonadiabatic process plays an important role. The non-adiabatic phenomena appear in many physical and chemical aswell as biological systems and have been investigated with a long history by the practical implementations of
numerical methods going beyond the purely theoretical stage but still in their infancy.
The treatment of non-adiabatic effects in molecular dynamics has become possible using the time-dependent
density functional theory (TDDFT). Saalmann [2] has proposed the non-adiabatic quantum molecular dynamics(NA-QMD) based on classical molecular dynamics for the nuclei self-consistently coupled with time-dependent
density functional theory for the electrons.
We have implemented this NA-QMD to our code TOMBO to simulate the chemical reactions in the excited stateof molecule. Here we use the all-electron mixed basis approach [3,4] which enables us to describe correctly thefree-electron continuum states as well as the bound and resonance states within the all-electron formalism, sinceboth plane waves and atomic orbital are used as basis function. As a case study, the reaction the reaction: CO + O+ CO was studied for comparison between adiabatic and non-adiabatic simulation. We found that the NAQMD
can even simulate this reaction with some initial velocities. We performed the reaction CO + O + CO in boththeories adiabatic and non-adiabatic with two cases: the middle oxygen atom had no initial velocity and had some
initial velocity. When the level crossing occurs, the non-adiabatic simulation gave the good results in comparewith adiabatic approximation.
1. M. Baer, Beyond Born-Oppeiheimer: Electronic Nonadiabatic Coupling Terms and Conical Intersection,Wiley,
Hoboken, NJ, 2006.
2. U. Saalmann and R. Schmidt, Z. Phys. D 38, 153 (1996).
3. K. Ohno, F. Mauri, and S. G. Louice, Phys. Rev B 87, 1009 (1997).
4. T. Ohtsuki, K. Ohno, K. Shiga, Y. Kawazoe, Y. Maruyama, and K.Masumoto, Phys. Rev. Lett 81, 967 (1998);
Phys. Rev. B 60, 1531 (1999).

P-14

Development of a time-dependent T-matrix theory
Kaoru Ohno, Shota Ono, Swastibrata Bhattacharyya,
Tomoyuki Horikiri, and Hideo Kosaka
Graduate School of Engineering, Yokohama National University, Japan
E-mail: ohno@ynu.ac.jp
It has been highly desired to go beyond the time-dependent density functional theory (TDDFT) within
the local (time and space) density approximation [1] in the investigation of time-dependent correlated
electron systems, because there is a delay in electron dynamics, and correlation between two electrons or
two holes cannot be treated in this framework. One possiblity to go beyond the TDDFT is to invoke thetime-dependent Green’s function formalism in the quentum many-body perturbation theory. For
example, the time evolution of the one-particle Green’s function may be described as [2]i∂G(r, r′; t − t′) = H 0 G(r, r′; t − t′) + ∫ Σ (r, r′′; t − t′′)G( r′′, r′; t′′ − t′)dr′′dt′′.
∂t(1)

Our idea is that, instead of solving this equation directly, one may solve the following time-dependent€

quasipartilce equation for the quasiparticle wave functions ϕ ν (r, t) :i∂ϕ ν (r, t) = H 0 ϕ ν (r, t) + ∫ Σ (r, r′; t − t′) ϕ ν ( r′, t′) dr′dt′.
∂t
€

(2)

Here we totally omitted the “retarded” symbol and “advanced” terms needed for the real time evoluation€

eqution for simplisity. In the present study, we generalize this naïve idea to the particle-particle channelof the two-particle Green’s function (T-matrix) in order to discuss the coherence and decoherence of twoelectrons (or two holes) in the system. Such a formulation would be very useful in a theory of quantum
entanglement or quantume teleportation from first principles.

[1] E. Runge and E. K. U. Gross, Phys. Rev. Lett. 52, 997 (1984).
[2] S. L. P. Kadanoff and G. Baym, Quantum Statitical Mechanics: Green's Function Methods inEquilibrium and Non-Equilibrium Problems (Advanced Book Classic) (Westview Press, 1994).

P-15

Semiconductor-water interfaces investigated by firstprinciple-calculations on boron-doped diamond
Z. Futera, T. Watanabe, Y.Einaga and Y. Tateyama Faculty of Science and Technology, Keio University, Japan
 CREST, Japan Science and Technology Agency (JST), Japan
International Center for Material Nanoarchitectonics (WPI-MANA),
National Institute for Materials Science (NIMS), Japan
 PRESTO, Japan Science and Technology Agency (JST), Japan Elements Strategy Initiative for Catalyst & Batteries, Koyoto University, Japan
Semiconductor/electrolyte interfaces represent one of the most challenging systems for theoretical andcomputational description because of their complexity, nevertheless their detail understanding is crucial
for modern electrochemistry, catalysis and batteries. Here, we investigated water interfaces ofsemiconductive boron-doped diamond (BDD) terminated by hydrogen (Fig. 1), oxygen, and hydroxyl
groups by using density functional theory (DFT)-based molecular dynamics [1]. We explained
experimentaly observed

reversibility / irreversibility of the as-grown / oxidized BDD electrodes,

respectively, by the BDD band position and subsurface band bending, which depend on the terminationand interfacial dipoles (Fig. 2). The reductive character of the H-terminated BDD is found, while theinterface covered by the carbonyl oxygen is clearly oxidative. The redox character of the hydroxyl
termination depends on the lateral hydrogen bonding network among the termination groups and israther oxidative at the water interface. We also examined the preference of the boron position in the
diamond and the stability of boron pairs and clusters. We suggest that the wide distribution of the single
boron dopants is crucial to the BDD conductivity, against the tendency of clustering. These results givenovel atomistic aspects of the termination and the boron doping effects on the BDD electrodes, which isuseful for further exploration of the efficient electrochemical application of BDD.
EC
EC

EF
EV

EF

⊕⊕⊕⊕
Eredox

BDD:H

EV

⊕⊕⊕⊕

BDD:H

Water

Eredox

Water

EC
EC

EF

EF
EV

EredoxBDD:OH,O

Fig. 1: Model of BDD:H/water interface

EV

⊕⊕⊕⊕

EredoxBDD:OH,O

Water

⊕⊕⊕⊕
Water

Fig. 2: Electronic states on BDD:H and BDD:O

1. Z. Futera, T. Watanabe, Y. Einaga and Y. Tateyama, J. Phys. Chem. C 118, 22040 (2014).

P-16

Reaction mechanism of dopachrome conversion,a precursor reaction of melanin biosynthesis:
implications for effects of pH and metal ions
Ryo Kishida*, Adhitya G. Saputro*, Nakanishi Hiroshi*,Wilson Agerico Diño*,** and Hideaki Kasai*,**,**** Graduate School of Engineering, Osaka University, Japan** Center for Atomic and Molecular Technologies, Osaka University, Japan*** Center for Continuing Professional Development, Osaka University, Japan
E-mail: kasai@dyn.ap.eng.osaka-u.ac.jp
Melanins are important pigments for biological systems. The protective functions of melanins against
harmful factors such as sunlight and reactive oxygen species have been well investigated. Exploration of
the relation among biosyntheses, structures/compositions and functions of melanin is an important issue
not only in biochemistry but also in condensed matter physics. Despite the efforts on investigating thechemical reactions involved in the melanin biosynthesis, there are still parts that need to be clarified. As
an important example, dopachrome conversion, a precursor reaction of melanin biosynthesis, has anelusive mechanism but is one of the major regulatory steps that would affect chemical
structure/composition of generated melanin. Dopachrome is a key precursor molecule that can convert
into two different molecules, 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid
(DHICA), which are known as building monomers of melanins. Experimental studies have revealed that
dopachrome spontaneously converts solely into DHI in aqueous solutions without any special factors andthat strongly acidic/basic pH and some divalent metal ions such as Cu(II) catalyze the formation of
DHICA. Basic pH and these metal ions have also been known to accelerate the conversion. However, themechanistic explanation for these findings has not been known. To provide the reasonable explanation forthese factors on the conversion, we carried out first-principles calculations based on density-functional
theory.[1] As critical elementary steps to be evaluated, we chose three dissociations, α-deprotonation,β-deprotonation and decarboxylation. The formation of DHI requires decarboxylation whereas DHICA
must be formed via α-deprotonation. The results showed that β-deprotonation is the rate-limiting step andthat protonations to quinonoid oxygens involved in dopachrome activate carboxyl group of dopachromefor decarboxylation. Furthermore, we found that Cu(II) coordination to the quinonoid oxygens markedly
decreases the activation barrier for β-deprotonation and protects the oxygens from protonations. Thesefindings describe the above-mentioned experiments at the atomic level.
1. R. Kishida, Y. Ushijima, A.G. Saputro and H. Kasai, Pigment Cell Melanoma Res. 27, 734 (2014).

P-17

Water rings at solid-liquid interfaces
K. Akagi
AIMR, Tohoku University, Japan
E-mail: akagi@wpi-aimr.tohoku.ac.jp
The structure of an aqueous solution at a solid-liquid interface is different from that of a bulk liquid, andeach solid-liquid interface shows its own characters such as hydrophilicity/hydrophobicity, relaxation
time, acidity/basicity, H/D exchange rate. However, while some of the physical properties(hydrophilicity/hydrophobicity, relaxation time, etc.) have been discussed well based on various
analyses, no clear picture how change in structure of the aqueous system at the interfacial region leads tothe chemical properties (acidity/basicity, H/D exchange rate, etc.) has been given so far.
In this presentation, we will see a certain type of hydrogen-bond analysis is very helpful to understandthe chemical characters of solid-liquid interfaces. The key component in this analysis is a “water ring”.
Of course, there are a lot of studies on hydrogen-bond network structures treating not only water rings
but also water cages or higher order graphs, but the fact that each hydrogen-bond has a direction (OH…O) and its arrangement is related to the stability of the ring structure has not been taken into accountappropriately. Actually, the water rings with regularly ordered cyclic hydrogen-bonds become longer
lived species compared to those with other type hydrogen-bonds in a bulk solution, but more important
finding is only these “regular rings” show repulsive interaction with H+ and OH− ions because of theirstability. Since the density of “regular rings” varies depending on the character of interfaces, thebehavior of H+ and OH− ions also changes reflecting it. As an example, H+ ions at the interface with
Pt(111) surface will be compared to those in a bulk liquid.
The results are mainly obtained by first-principles molecular dynamics calculations with the GGA/PBE
functional, but it was also confirmed that this concept is robust against difference in the functional types.

P-18

Nonequilibrium dynamical cluster approximation: nonlocal correlation and real-time dynamics
N. TsujiDepartment of Physics, The University of Tokyo, Japan
E-mail: tsuji@cms.phys.s.u-tokyo.ac.jp
Nonequilibrium dynamics in strongly correlated systems has attracted much attention due to theexperimental development of time-resolved measurement techniques in solid-state and cold-atomsystems. From the point of view of `computics’, it can be seen as a great challenge to treat both strong
correlation and nonequilibrium states simultaneously for interacting many-body systems of large size.
Nonequilibrium dynamical mean-field theory (DMFT) has been established as a powerful approach to
tackle such a problem [1]. The limitation of the nonequilibrium DMFT, however, is the local
approximation of the self-energy, which is justified in the large dimensional limit of lattice models.
Here we propose the nonequilibrium dynamical cluster approximation (DCA) [2], one of cluster
extensions of the nonequilibrium DMFT. It maps a lattice model into a cluster model embedded in areal-time dynamical mean field (Fig. 1). The short-range correlations within the cluster is systematicallytaken into account. We apply the nonequilibrium DCA to the one and two-dimensional Hubbard model,
and discuss the effect of non-local correlations on the relaxation and thermalization processes.
clust
Glat
I J (t, t ) = G I J [I J ](t, t )self-consistency
condition
I, J

i, j
lat
i j (t, t ) =clust
I J (t, t )0(i, j)(i, j)

clusterclusterFig. 1. The schematic algorithm of the nonequilibrium dynamical cluster approximation.
1.

H. Aoki, N. Tsuji, M. Eckstein, M. Kollar, T. Oka, and P. Werner, Rev. Mod. Phys. 86, 779 (2014).

2.

N. Tsuji, P. Barmettler, H. Aoki, and P. Werner, Phys. Rev. B 90, 075117 (2014).

P-19

Non-equilibrium DMFT study of thermalizationin an electron-phonon system
Y. Murakami*, P. Werner**, N. Tsuji* and H. Aoki** Department of Physics, The University of Tokyo, Japan
E-mail: murakami@cms.phys.s.u-tokyo.ac.jp** Department of Physics, University of Fribourg, Fribourg, Switzerland
There is a surge of interest in the non-equilibrium properties of condensed-matter systems. In realmaterials, electron-phonon (EP) interactions can play an important role in the non-equilibrium dynamics.
While there have been some attempts to compute the dynamics beyond the conventional Boltzmann
equation, we are still far from a full understanding. In particular, it is important to understand thefeedback from the excited quantum phonons to the electrons. Motivated by this, we develop a numericalmethod based on the non-equilibrium dynamical mean-field theory (DMFT) [1] and the self-consistent
Migdal approximation, and investigate the dynamics of an electron-phonon system described by theHolstein model after a sudden change of the EP coupling [2].
We have found that the nature of the relaxation exhibits a qualitative change (“thermalization
crossover”) as the EP coupling is increased. In the sufficiently weakly correlated regime, phonon
oscillations are damped rapidly compared to the electron relaxation, while in the stronger-coupling
regime the situation is reversed, see Fig (a). The crossover is clearly reflected in the time evolutions of
the momentum distribution and spectral functions. The physical origin of this “thermalization crossover”
is a different dependence of the electron and phonon quasi-particle lifetimes on the EP coupling. In
addition, we discuss the importance of the dynamics of quantum phonons by comparing these resultswith those of the Hartree-Fock (HF) approximation. The latter does not consider the dynamics ofphonons and hence describes a qualitatively very different relaxation process (Fig (b)).
Fig. (a) Plot of different
energy scales against
the EP coupling. (b)Comparison

betweenthe Migdal and the HF
approximation.

1. H. Aoki, N. Tsuji, M. Eckstein, M. Kollar, T. Oka and P. Werner, Rev. Mod. Phys. 86, 779 (2014).
2. Y. Murakami, P. Werner, N. Tsuji and H. Aoki, arXiv:1407.8288 (2014).

P-20

Nonequilibrium dynamics of dissipative excitons incarbon nanotubes
Y. Yamada, Y. Yamaji, and M. Imada
Department of Applied Physics, Graduate School of Engineering, The University ofTokyo, Japan
E-mail: yamada@solis.t.u-tokyo.ac.jp
The low-dimensional optoelectronic materials, such as nanotubes, quantum dots and organic molecules,
have been intensively studied, as promising candidates for improving the efficiency of photovoltaic
devices beyond the Shockley-Queisser limit in the conventional semiconductors. In particular,
semiconducting single-walled carbon nanotubes are one-dimensional materials with remarkably highabsorption rate of light [1] where the excitons play an important role in the energy-conversion from lightto electricity. Though some time-resolved photoluminescence experiments have been conducted toinvestigate the relaxation pathway of the bright exciton [2,3], the pathway has not been fully understoodbecause several dark excitons that cannot be directly detected by photoluminescence are expected toexist.
In this study, we theoretically investigate nonequilirium quantum dynamics of the dissipative excitonic
system in a single-walled carbon nanotube after the absorption of a photon. The system consists of one
bright and two dark excitons that interact with phonons and a dissipative photon. With using the
combined method of the generalized quantum master equation and photocounting, we show that theenergy dissipation with the quantum decoherence by the phonons gives a fast irreversible energy transferfrom the bright exciton to the dark ones, which is consistent with the results of the photoluminescence
experiments [2,3]. Since the dark excitons have by far longer lifetimes than that of the bright one, thedark excitons contribute to a reduction of the recombination rate of the electron and hole after the lightabsorption, which are expected to improve efficiency of photovoltaics.
1. K. Mizuno et al., Proc. Natl. Acad. Sci. U.S.A. 106, 6044 (2009).
2. S. Berciaud, L. Cognet, and B. Lounis, Phys. Rev. Lett. 101, 077402 (2008).
3. J. G. Duque, M. Pasquali, L. Cognet, and B. Lounis, ACS Nano 3, 2153 (2009).

P-21

Fermi Energy Dependence of High-Frequency Coherent
Phonons in Metallic Carbon Nanotubes
I. Katayama *, K. Maekawa*, K. Sato*, Y. Minami*, K. Yanagi**, M. Kitajima*
and J. Takeda** Graduate School of Engineering, Yokohama National University, Japan
E-mail: jun@ynu.ac.jp** Graduate School of Science and Engineering, Tokyo Metropolitan University,
Japan
Carbon nanotubes (CNTs) consist of graphene sheets rolled up to form one-dimensional
cylinder structure, which results in unusual electronic structures such as van-Hove singularities in thedensity of states. CNTs can either be semiconductors or metals, depending on the structure specified by
the so-called chiral vector [1]. Metallic CNTs are of particular interest because they exhibit strong
electron-phonon coupling due to Kohn anomaly, and thus the phonon properties show drastic
dependence on the Fermi energy and the non-equilibrium electron distribution [2-4]. In order to reveal
such dependence of the dynamics of phonons, we investigated coherent phonon signals by changing the
Fermi energy, which are inaccessible with the conventional Raman spectroscopy.
Thin films of metallic single-walled CNTs with average diameters of 1.4 nm were obtained bypurification using density-gradient ultracentrifuge method from initial SWCNTs produced by an arcdischarge (Arc-SO, Meijo nano-carbon Co.) [5-6]. We used an ionic liquid (TMPA-TFSI, KantoKagaku Co.) for electrolyte solution. A 7.5-fs Ti-sapphire laser (center wavelength of 800 nm, repetition
rate of 80 MHz, and output power of 200 mW) was used for pump-probe transmission measurements.
The amplitudes, frequencies and phases of the observed coherent phonons in CNTs depend strongly on
the gate voltage. These dependence indicates the effect of Kohn anomaly to the G, D, 2G and 2D
coherent phonons in CNTs, in which the phonon softening and enhanced dephasing are observed at the
Dirac point. Time-dependent frequency-shift of the G-mode was also observed demonstrating that our
method for applying the gate voltage is promising for investigating ultrafast dynamics of coherent
phonons with different chemical potentials.
1. S. Reich, C. Thomsen, and J. Maultzsch, Carbon Nanotubes: Basic Concepts and Physical Properties(Wiley-VCH, Berlin, 2004).
2. J. Yan, et al., Phys. Rev. Lett. 98, 166802 (2007).
3. H. Farhat, et al., Phys. Rev. Lett. 99, 145506 (2007).
4. K. Ishioka, et al., Phys. Rev. B 77, 121402 (2008).
5. K. Yanagi, et al., Adv. Mater. 23, 2811 (2011).
6. S. Ghosh, et al., Nat. Nanotech. 5, 443 (2010).

P-22

Nonlinear Dynamics of Electrons on Dirac-Like Bandin Semi-Metal Bismuth Induced by an THz Electric Pulse
Y. Minami*, K. Araki*, T. D. Dao**,***, T. Nagao**,***,J. Takeda, M. Kitajima*-****, and I. Katayama**Graduate School of Engineering, Yokohama National University, Japan
E-mail: minamiyasuo@ynu.ac.jp**WPI-MANA, National Institute for Materials Science, Japan***JST-CREST, Japan****LxRay Co. Ltd., Japan
Bismuth (Bi) is one of the typical semimetals, which is extensively studied because of its
anomalous properties such as spin-orbital interactions, the long Fermi wavelength, and so on.
In this study, we observed nonlinear-electron dynamics at L point in the Brillouin zone in Bi
with intense terahertz time domain spectroscopy[1, 2]. The band structure at L point is Dirac-like cone
and approximated by a hyperbolic curve;E  m02 c 4  p 2 c 2 ,(1)where m0 is the rest mass, and c is the “light velocity” in the E - p space at the weak-magnetic-field
limit [3, 4]. m0 c2 corresponds to the rest energy in the special relativistic theory. We also evaluated therelativistic beta  to quantify the deviation from the Newtonian mechanics, which is defined as v / c( v ; particle velocity) [5-7]. Equation of motion for the electrons in Bi under an electromagnetic field
can simply be described asdp  t   p  t   eEtr  t  .
dt(2)Here, p  t  is the kinetic momentum of electrons,  is the damping constant, e is the elementary charge,
and Etr  t   Ein  t   Eem  t  is the electric field at the film which is the same as transmitted electric field
through the specimen. Here, Ein  t  and Eem  t  are the incident electric field and emitted electric fieldfrom the specimen [8].
In our calculation, the electrons were accelerated near the “light velocity” with a relativistic
beta of  ~ 0.92 along the almost linear band structure of Bi, in which the relativistic dynamics
dominates the motion of the electrons. As a result, the electron mass was enhanced by 2.6 times.
1. Y. Minami, T. Kurihara, K. Yamaguchi, M. Nakajima, and T. Suemoto, Appl. Phys. Lett. 102,
041105 (2013).
2. H. Hirori, A. Doi, F. Blanchard, and K. Tanaka, Appl. Phys. Lett. 98, 091106 (2011).
3. S. A. Mikhailov and K. Ziegler, Phys. Rev. Lett. 99, 016803 (2007).
4. B. Lax, B., J. G. Mavroides, H. J. Zeiger, and R. J. Keyes, Phys. Rev. Lett. 5, 241 (1960).
5. J. F. Sherson, C. Weitenberg, M. Endres, M. Cheneau, I. Bloch, and S. Kuhr, Nature 467, 68 (2010).
6. D. Hsieh, D. Qian, L. Wray, Y. Xia, Y. S. Hor, R. J. Cava, and M. Z. Hasan, Nature 452, 970 (2008).
7. K. S. Novoselov et al., Nature 438, 197 (2005).
8. W. Kuehn, P. Gaal, K. Reimann, M. Woerner, T. Elsaesser, and R. Hey, Phys. Rev. Lett. 104, 146602(2010).

P-23

Single-shot visualization of ultrafast amorphization inchalcogenide alloy thin films
W. Oba*, I. Katayama*, Y. Minami*, T. Saiki** and J. Takeda** Graduate School of Engineering, Yokohama National University, Japan
E-mail: jun@ynu.ac.jp** Graduate School of Science and Technology, Keio University, Japan
Single-shot visualization of ultrafast crystalline-to-amorphous phase-change in chalcogenide alloy thinfilms, GeTe and Ge2Sb2Te5 (GST) thin films, has been demonstarted using single-shot real-time pumpprobe imaging spectroscopy with an echelon mirror [1-3]. Using the 10 nm-thick chalcogenide alloy
films, a nearly homogeneous photoexcitation on the crystalline-to-amorphous phase change could beachieved, allowing us to quantitatively evaluate the amorphization dynamics. The observed rise time toreach the amorphization was found to be 130-200 fs [4], which was in good agreement with the half
period of the A1 phonon frequency in the octahedral GeTe6 structure [5]. This result strongly suggeststhat the ultrafast amorphization can be attributed to the rearrangement of Ge atoms from an octahedral
structure to a tetrahedral structure, which was proposed by the first-principle calculations [6,7]. We also
examined the stability of the photoinduced amorphous phase as a function of the pump laser fluence.
Below the critical laser fluence, the photoinduced amorphous phase reverted to the crystalline phase
after long delay times. In contrast, above the critical laser fluence, the domain size became sufficiently
large that the photoinduced amorphous phase was stabilized, and as a result, a permanent amorphousrecording mark was formed in chalcogenide alloy thin films.
1. I. Katayama, H. Sakaibara, and J. Takeda, Jpn. J. Appl. Phys. 50, 102701 (2011).
2. H. Sakaibara, Y. Ikegaya, I. Katayama, and J. Takeda, Opt. Lett. 37, 1118 (2012).
3. Y. Minami, H. Yamaki, I. Katayama, and J. Takeda, Appl. Phys. Exp. 7, 022402 (2014).
4. J. Takeda, W. Oba, Y. Minami, T. Saiki, and I. Katayama, Appl. Phys. Lett. 104, 261903 (2014).
5. K. Makino, J. Tominaga, and M. Hase, Opt. Exp. 19, 1260 (2011).
6. A. V. Kolobov, A. S. Mishchenko, P. Fons, S. M. Yabubenya, and J. Tominaga, J. Phys. Condens.
Mat. 19, 455209 (2007).
7. Xian-Bin Li, X. Q. Liu, Xin Liu, Dong Han, Z. Zhang, X. D. Han, Hong-Bo Sun, and S. B. Zhang,Phys. Rev. Lett. 107, 015501 (2011).

P-24

Quantum or thermal fluctuation on molecules in solution
Y. Kanematsu*, T. Mashiko* and M. Tachikawa** Quantum Chemistry Division, Yokohama-City University, Seto 22-2, Kanazawa-ku,
Yokohama 236-0027, Japan,
E-mail: n115302f@yokohama-cu.ac.jp; tachi@yokohama-cu.ac.jp
We would like to report the first theoretical analysis on NMR isotope shifts of photoactive yellow
protein (PYP) by “ONIOM(MC_QM:MM)”, which we newly developed on the combination of ONIOM
and multicomponent quantum mechanics (MC_QM)[1]. PYP is one of the most studied photosensing
proteins, whose chromophore, p-coumaric acid (pCA), forms hydrogen bonds (H-bonds) withneighboring residues, Tyr42 an Glu46 in the dark state (Fig. 1). After comprehensive analyses ongeometry and chemical shift of PYP by crystallography, liquid NMR, and theoretical calculation, it wassuggested that low barrier H-bond (LBHB) would be possible
between pCA and Glu46 under the crystallographic condition withvicinyl Arg52 deprotonated, while conventional H-bond would beformed in liquid water where Arg52 was presumably protonated[2].
To validate the above suggestion, we calculated NMR isotope shift
of

PYP

by

ONIOM(MC_QM:MM)

comparingwithcorresponding experimental values.
Table 1 shows the isotope shifts on the hydroxylhydrogens of Tyr42 and Glu46 for models of protonated (p)and deprotonated (dp) Arg52 with or without the aqueous
solvent effect of polarizable continuum model (PCM)
around the protein. We can see that the best agreement withtheFig.1. H-bonds in PYP.
X is null(for dp model) or H+ (p model)
Table
1.
Computational
andexperimental NMR isotope shift [ppm]
Tyr42 Glu46
ONIOM-dp
-0.34
-0.18
ONIOM-dp/PCM
-0.28
-0.27
ONIOM-p/PCM
-0.18
-0.17
exptl.[3]
-0.21
-0.19

experimental values were obtained for the ONIOM-p/PCM
model. Consequently, the protonation of Arg52 in aqueous
solution is validated by our calculatoin, which is reasonablegiven that the this basic residue is exposed to the solvent
and the solvent was neutral (pH=7.2) in the experimental
condition[3]. The discussion about the LBHB formation
will be also shown in the presentation.
Thermodynamics on gear-shaped amphiphileFig.2. Chemical formulae of gearshaped amphiphile molecules, 1 (R =CH3) and 2 (R = H).

molecules (Fig. 2) in solution will be also discussed.
1. M. Tachikawa, K. Mori, H. Nakai, and K. Iguchi, Chem. Phys. Lett. 290, 437 (1998)
2. M. Nadal-Ferret, R. Gelabert, M. Moreno, J. M. Lluch, J. Am. Chem. Soc. 136, 3542 (2014)
3. P. A. Sigala, M. A. Tsuchida, D. Herschlag, Proc. Natl. Acad. Sci. 106, 9232 (2009)

P-25

Electronic structure of a Cerasome Model
Masato Oda
Dpeartment of Materials Science and Chemistry, Wakayama University, Japan
E-mail: moda@sys.wakayama-u.ac.jp

Recently, utilization of cerasomes, lipid bilayer vesicles (so-called liposome) reinforced
its surface with siloxane bond [1], for drug or gene delivery systems has attracted muchinterest. Although there are lots of research for application, basic properties of thecerasome such as microscopic structures and electronic states have not been cleared yet.
The purpose of this study is to investigate the basic properties of a model structure of
the cerasome.
To model the cerasome, we approximate a spherical vesicle to plane membrane andassume closed packing configuration. The calculation model is shown in fig. 1. We
calculate the electronic structures of the model using the first principles method basedon the density functional theory. Comparing the electronic DOS of the membrane modelwith that of the molecule reveals that there are mid-gap states in the membrane modelthat are not in the molecule. These mid-gap states are caused by antibonding states of
Si-C bonds that connect the siloxane network and the organic parts of the lipid.

Figure 1: Schemacit picture of the cerasome model
1.

K. Katagiri, at. al., J. Chem. Lett. 28, 661, 1999.

2.

S. Yabushita, at. al., JSSNT 12, 112, 2014.

P-26

Computational analysis of the molecular interactions insecondary structures of proteinsY. Takano*,**, A. Kusaka*, H. Nakamura** Institute for Protein Research, Osaka University, Japan
E-mail: ytakano@protein.osaka-u.ac.jp** JST-CREST, JapanThe three-dimensional structure of a protein determines its functions and chemical properties. The
second structures such as α-helices and β-sheets are important components for the protein architecture.
The molecular interactions, in particular hydrogen bonding, play significant roles in the formation of thesecondary structures. Quantitative estimate of these interactions is required to understand the principleof the formation of the three-dimensional protein structure.
Our goal is to improve the force field for accurate description of protein behavior. To address the goal,
we have investigated the molecular interactions in the α-helices (AH) and parallel and antiparallel βsheets (PB and APB) composed of alanine residues, using quantum chemical (QC) methods (B97D/631+G(d) [1]) and molecular mechanics (MM) (AMBER99-SB [2]). The characteristic interactions
essential for forming the secondary structures are discussed quantitatively. The MM force fieldoverestimates the interaction energies of the α-helix, compared to those of the β-sheet, implying that the
improvement of the electrostatic and hydrogen bonding interactions in the force field are required.
We have also evaluated each hydrogen bond (H-bond) energy in the α-helices and the β-sheets by using
the molecular tailoring approach (MTA) [3], which is one of the fragment-based methods. Within MTA,a large system is divided into some subsystems. The electronic properties of the subsystems arecomputationally evaluated. The properties of the large system are obtained by patching thecorresponding properties of all the subsystems. MTA shows that the H-bonds in the β-sheets arestronger than those in the α-helices due to the structural constraint in α-helix and that the antiparallel βsheet can form linear H-bonds rather than the parallel β-sheet, resulting in the stronger H-bonds in the
antiparallel β-sheet. In addition, the H-bonds in the α-helices can be classified three types: N-terminal,
C-terminal, and inner H-bonds, and inner H-bonds are weaker than other H-bonds at the same H-bonddistances. The difference of the H-bond energies between the parallel and antiparallel β sheets andbetween the N-terminal, C-terminal, and inner H-bonds in the α helices indicate secondary-structure
dependence on the H-bond energies.
1. S. Grimme, J. Comput. Chem. 27, 1789-1799 (2006).
2. J. Wang, P. Cieplak, P. A. Kollman, J. Comput. Chem. 21, 1049-1074 (2000).
3. M. M. Deshmukh, S. R. Gadre, J. Phys. Chem. A 113, 7927-7932 (2009).

P-27

Dynamics of 10-Residue Peptide, Chignolin,
Studied by Relaxation Mode Analysis
Ayori Mitsutake*,** and Hiroshi Takano**Department of Physics, Keio University**JST, PREST
E-mail: ayori@mail.rk.phys.keio.ac.jp
Biopolymers have flexible structures and several varieties of functions. The functions are derived
from not only structures but also the structural fluctuations. Therefore, the properties of structuralfluctuations of biopolymers are important for understanding the interrelationship between its movement
and functions. Principle component analysis is one of the most popular methods for analyzing the static
properties of structural fluctuations. The method treats “static” information although it is applied inmany simulations of protein systems.
Relaxation mode analysis (RMA) developed to investigate “dynamic” properties of polymer, homopolymer, systems [1,2]. In the method, slow relaxation modes are extracted from trajectory. In the caseof liner polymers, the relaxation phenomena have been studied systematically in terms of the relaxation
modes and rates. The relaxation modes { X p } satisfy

X p (t)X q (0) = ! p,q exp(!" pt) , whereX p (t)X q (0) denotes the equilibrium correlation of X p at time t and X q at time 0 and ! p is called
the relaxation rate of X p . In RMA, the time correlation matrices of structural fluctuations for two

different times are calculated. Then, by solving a generalized eigenvalue problem for these matrices, therelaxation rates and modes are estimated from the eigenvalues and eigenvectors, respectively.
RMA has been applied to protein, hetero-polymer, systems to investigate dynamic properties ofstructural fluctuations [3,4]. Here, we present results of relaxation mode analysis for a simulation ofchignolin at a transition temperature.
References[1] H. Takano and S. Miyashita, J. Phys. Soc. Jpn. 64, 3688 (1995).
[2] H. Hirao, S. Koseki, H. Takano, J. Phys. Soc. Jpn. 66, 3399 (1997).
[3] A. Mitsutake, H. Iijima, H. Takano, J. Chem. Phys.135, 164102 (2011).
[4] T. Nagai, A. Mitsutake, and H. Takano, J. Phys. Soc. Jpn. 82, 023803 (2013); T. Nagai, A. Mitsutake,
H. Takano, Seibutsu Butsuri (Biophysics), 49, Supplement S75, (Abstracts for the 47st annual meeting,
The Biophysical Society of Japan) (2009)

P-28

Theoretical Study of the electron transfer reaction by
DNA photolyase
R. sato*, H. N. Kitoh*, T. Kawatsu**,***, K. Yura****, K. Ando*****, T. Yamato** Graduate School of Science, The University of Nagoya, Japan
E-mail: rsato@tb.phys.nagoya-u.ac.jp** Graduate School of Nanobioscience, The Yokohama City University, Japan*** Graduate School of Arts and Science, The Tokyo University, Japan**** Graduate School of Humanities and Science, The Ochanomizu University, Japan***** Graduate School of Science, The Kyoto University, JapanDNA photolyase (PHR) is a blue-light photoreceptor that use light energy in the UV-A/blue region. This
enzyme repair cis-syn cyclobutane pyrimidine dimer (CPD) and (6-4) pyrimidine-pyrimidine lesion (6-4
photoproduct) by electron transfer (ET) reaction [1] and proton transfer reaction [2], respectively. The
former uses a cyclic ET reaction between flavin adenine dinucleotide (FAD) and CPD. However, themolecular mechanism of the this ET has not been fully understood yet . Recently, we performed acomputational study on the ET reaction of the DNA photolyase derived from A. nidulans. We identified
an importrant amino acid residue, Met353, at which busy traffic of electron tunneling current wasobserved. Interestingly, we found that the residue is perdectly conserved among the sequences of ClassI CPD photolyase subfamily [3]In this work, the molecular mechanism involved in the efficient electron transfer of DNA photolyase
was investigated by the analysis of electron tunneling pathways from FADH- to CPD using ab initio andfragment molecular orbital calculations. In particular, we focused on the roles of amino acid residues
and crystallographic water moleculars in the active site.
1.

L. 0. Essen and T. Klar, Cell . Mol. Life. Sci, 63, 1266 (2006).

2.

J. Li et al, Nature, 466, 886 (2010).

3.

Y. Miyazawa et al, Biophys. J, 94, 2194 (2008).

P-29

Sacrificial anion reduction mechanism forelectrochemical stability improvement in highly
concentrated Li-salt electrolyte
Keitaro Sodeyama*,**, Yuki Yamada*,***, Atsuo Yamada*,***, andYoshitaka Tateyama*,**,*****ESICB, Kyoto University, **MANA, NIMS, ***Department of Chemical System
Engineering, The University of Tokyo, ****JST-PRESTO and CREST
E-mail: SODEYAMA.Keitaro @nims.go.jp
Li-salt concentration has been recently proposed as an important control parameter of reduction stabilityof electrolytes in Lithium-ion battery (LIB). Here we theoretically investigated low (LC) and high (HC)concentration systems of LiN(SO2CF3)2 (Li-TFSA) salt in acetonitrile (AN) solution, to elucidate themechanism of improving the low reduction stability of AN at the HC condition, by density functional
theory based molecular dynamics (DFT-MD) sampling of the solvation character with extra electron(s).
We demonstrated that TFSA anions sacrificially accept the reductive electron at the HC condition,
which is ascribed to formation of specific network structure and the resulting shift of electron affinity of
the anions. We also found that, even in the LC condition, TFSA eventually decomposes with one
electron reduction. To confirm the 1e reduction stability of AN molecules, we also explored reaction
barrier height of the AN decomposition reaction with Blue-moon ensemble technique. Figure 1 shows
the free energy profile of AN decomposition
under 1e reduction. The barrier is around 60
kcal/mol, and the product is unstable rather
than the intact AN cases. Therefore, we
confirmed that the 1e reduced AN does notdecompose and we found that 2e reduction
is required for AN decomposition. The
sacrificial anion reduction hinders the twoelectrons reductive decomposition of AN,leadingtoimproved

electrochemical

stability. The mechanism may give a
guiding principle for the design of better
LIB electrolytes.

Figure1: Free energy profiles, A, of 1e reductive
decomposition of AN along the mechanicalconstraint .

1. Y. Yamada, K. Furukawa, K. Sodeyama, K. Kikuchi, M. Yaegashi, Y. Tateyama, A. Yamada, J. Am.
Chem. Soc., 136, 5039 (2014). 2. K. Sodeyama, Y. Yamada, K. Aikawa, A. Yamada, Y. Tateyama, J.
Phys. Chem. C, 118, 14091 (2014).

P-30

DFT+U investigation of oxide cathode/sulfide electrolyte
interface for all-solid-state Li-ion batteries
J. Haruyama*, K. Sodeyama* **, K. Takada* and Y. Tateyama* ** **** WPI-MANA and GREEN, National Institute for Materials Science (NIMS), Japan
E-mail: HARUYAMA.Jun@nims.go.jp** Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto Univ., Japan*** PRESTO and CREST, Japan Science and Technology Agency (JST), Japan
We investigated interfaces between LiCoO2 (LCO) cathode and β-Li3PS4 (LPS) solid electrolyte withand without LiNbO3 (LNO) buffer layers (Fig. 1) in order to reveal interfacial resistance arising between
oxide cathode/sulfide electrolyte interfaces in all solid-state lithium-ion batteries (ASS-LIBs). [1] The
density functional theory (DFT) + U calculations, coupling with a systematic procedure for interface
matching, showed the stable structures and the electronic states of the interfaces. The LCO/LPS
interface has attractive Li adsorption sites and rather disordered structure, whereas the interposition of
the LNO buffer layers leads smooth interfaces without these attractive sites. The calculated energies for
the Li-vacancy formation suggest space–charge layer (SCL) growth at the beginning of charging, arising
the high interfacial resistance. The LNO interposition suppresses this growth of SCL and provides
smooth Li transport paths free from the possible bottlenecks. These aspects on the atomic scale will givea useful perspective for the further improvement of the ASS-LIB performance. [2]Fig. 1. Surface structures of (a) LCO (110), (b) LNO ( 1 10 ), (c) LNO (110) and (d) LPS (010). We
construct LCO/LNO, LCO/LPS, and LNO/LPS interfaces from these surfaces.
1. N. Ohta, K. Takada, L. Zhang, R. Ma, M. Osada and T. Sasaki, Adv. Mater. 18, 2226 (2006).
2. J. Haruyama, K. Sodeyama, L. Han, K. Takada and Y. Tateyama, Chem. Mater. 26, 4248 (2014).

P-31

Ru Dye–Organic Dye Interaction on TiO2 in CoSensitized Dye-Sensitized Solar Cell: DFT investigation
Y. Ootani1,2, K. Sodeyama1,3, L. Han1,2, and Y. Tateyama1,2,3,4
1)
National Institute for Materials Science, 2)CREST, Japan Science and Technology
Agency, 3)Elements Strategy Initiative for Catalysts & Batteries, Kyoto University
4)
PRESTO, Japan Science and Technology Agency
E-mail: OTANI.Yusuke@nims.go.jp
Dye-sensitized solar cell (DSC) have been widely studied as a(a) N3-HSQ1

next-generation photovoltaic device. In the DSC, the photoexcited
dye injects the excited electron to TiO2 electrode to generate theelectronic current. A central issue for the higher power conversion
efficiency (PCE) is to improve the light harvest efficiency (LHE).
One of the promising way is the co-sensitization approach, in which(b) N3-SQ1

two dyes having complementary absorption properties are mixed.
However, not all the co-sensitized DSC shows the improved PCE,
and detailed design principle is still not clear. Recently, N3 based
co-sensitized DSCs were developed with cis- and trans-configured
squaraine dyes, HSQ1 and SQ11. While the N3-HSQ1 co-sensitized
DSC showed the improved PCE compared to N3 DSC, N3-SQ1

Figure 1. The co-adsorption

DSC showed the lower PCE. This result indicates that there are

structures.

significant differences between N3-HSQ1 and N3-SQ1 interaction.
In this work we investigated the N3–squaraine dye interaction on TiO2 by means of DFT calculations.
The co-adsorption structures of N3-HSQ1 and N3-SQ1 were explored and electronic structures areanalyzed. Although, HSQ1 and SQ1 have a similar structre, there is a notable difference in coadsorption structure. In the co-adsorption structure of N3-HSQ1, a steric hindrance keeps N3–HSQ1
distance longer. On the other hand, SQ1 form the hydrogen bond (HB) with N3 (Figure 1). It is wellknown that the dye aggregation leads an excitation quenching. Moreover, an absorption peak of SQ1
shift to short wavelength. Since the SQ1 is designed to extend the absorption range to long wavelength,
this shift is undesirable. We concluded that the slight molecular configulation difference affects theintermlecular interaction on the TiO2 surface, leading the differences in the PCE of co-sensitized DSC.
1. C. Qin, et al. Adv. Funct. Mater. 23, 3782 (2013).
2. Y. Ootani, K. Sodeyama, L. Han and Y. Tateyama in preparation.

P-32

Water adsorption and dissociation at metal-supported
ceria thin films: Thickness and interface-proximity effects
studied with DFT+U calculations
L. Szabova*, V. Matolin**, S. Fabris*** and Y. Tateyama***** MANA, National Institute for Materials Science (NIMS), Tsukuba, Japan
E-mail: Szabova.Lucie@nims.go.jp** Charles University in Prague, Czech Republic** CNR-IOM DEMOCRITOS and SISSA, Trieste, Italy** MANA, NIMS, Tsukuba and Kyoto University and ESICB and JST-PRESTO, Japan
The present work is a theoretical analysis based on numerical DFT+U simulations investigating thephysical and chemical properties of ultrathin ceria films supported by Cu(111). Such materials exhibit
high activity towards several important reactions in heterogeneous catalysis such as water-gas shift [1]and CO oxidation [2], with important applications also for renewable energy technologies such as fuelcells.
We provide evidence of the influence of film thickness on the electronic and structural properties as wellas on the reactivity of new materials consisting of ultrathin ceria films supported on Cu(111). The
calculations show that one monolayer thin film of ceria on Cu exhibits differences in strain buildup,
charge and the atomistic structure compared to thicker ceria layers on Cu. These distinct properties of thefirst monolayer are ascribed to pronounced finite size effects when the limiting thickness of the oxide andthe proximity of the metal substrate cause significant rearrangement of charges compared to thicker ceria
slabs [3].
The thickness of the film has strong influence also on the reactivity of thin ceria films. The adsorption
and dissociation properties of water are strongly affected by size and electronic effects. The water
adsorption is more stable on 2 monolayer film than on 1 monolayer ultrathin film or thick ceria slabs.
The unique structural flexibility and electronic properties of the ultrathin 1ML ceria film supported bycopper allows for stronger bond for the completely dissociated water accompanied by strong relaxation
upon dissociation.
1. J. A. Rodriguez, S. Ma, P. Liu, J. Hrbek, J. Evans, M. Perez, Science 318, 1757 (2007).
2. W. Liu and M. Flytzani-Stephanopoulos, J. Catal. 153 (1995).
3. L. Szabová, O. Stetsovych, F. Dvorak, M. Farnesi Camellone, S. Fabris, J. Myslivecek, V. Matolin, J.
Phys. Chem. C 116, 6677–6684 (2012).

P-33

Two-component density functional theory of positronstate at lithium adsorbed Al(100) surface
S. Hagiwara, C. Hu and K. Watanabe
Department of Physics, Tokyo University of Science, Japan
E-mail: 1213623@ed.tus.ac.jp
The positrons that are slowly (~10eV) incident to metals are immediately thermalized by plasmon,
phonon and/or other excitations [1]. Thus, the positrons return from the bulk to the metal surface via
thermal diffusion, resulting in the trapped state of the surface image potential [2]. The trapped positrons
are found to annihilate with surface electrons, generating some γ-rays that manifest the surface
electronic states. For this reason, the positron is a very powerful tool for the surface analysis. However,the surface states of the positron have not been fully investigated. In particular, the first-principles
simulations on this topic using the real surfaces of atomic and electronic structures that are fully relaxedhave not been performed. In the present study, we aim to understand the basics of positron surface
states of metal surface using lithium (Li) adsorbed Al(100) surface by the two-component density
functional calculation [3, 4].
To study the positron surface-state properties using the slab calculations, we have implemented thecorrugated mirror model for the surface image potential as well as the the ramp potential for the effect of
the band-shift energy in the program package, ABINIT [5].
Our results are in good agreement with experimental data. Positron lifetime reflects the electron andpositron surface distributions. The values of positron surface binding energy depend on the change of
surface dipole barrier. The results of the work functions and activation energy for Li adsorbed Al(100)surface suggest that the positron is reemitted as the positronium that is a bound state of an electron and apositron. We will discuss the details of the results for positron surface states in the presentation.
1. W. Barandt and A. Dupasquier (Eds.) : Positron Solid State Physics ( Proceedings of theInternational School of Physics “Enrico Fermi” ) (1983, Elsevier Science Ltd. ).
2. P. J. Schultz and K. G. Lynn, Rev. Mod. Phys. 60, 701 (1988).
3. M. J. Puska and R. M. Nieminen, Rev. Mod. Phys. 66, 841 (1994).
4. M. Saito, A. Oshiyama, and S. Tanigawa, Phys. Rev. B 44, 10601 (1991).
5. X. Gonze et. al., Comput. Phys. Commun. 180, 2582 (2009).

P-34

First-principles study of spin-polarized positron lifetimes
in ferromagnets
J.Lin*, T.Yamasaki** and M.Saito**** International Center for Materials Nanoarchitectonics, Tsukuba, Japan
E-mail: LIN.Jianbo@nims.go.jp** National Institute for Materials Science, Tsukuba, Japan*** Graduate School of Natural Science and Technology, Kanazawa University,
Kanazawa, Japan
A positron annihilation experiment is a powerful tool to study electronic structure of materials especially
defects related to vacancy. Previous experimental study of Doppler broadening of annihilation radiation
find that the electron momentum distributions of majority spin and minority spin show some difference inthe case of Fe, Co, Ni and Gd polycrystals under the external magnetic field 1T at room temperature [1].
It is thus expected that the positron lifetimes of majority spin and minority spin are different. However,theoretical studies of spin-polarized positron lifetimes are rare. What’s more, it is important to know if
spin-polarized positron annihilation experiment has application to ferromagnets or to spintronics in the
future.
In this study, we carry out spin-polarized positron lifetime calculations of Fe, Ni, and Co crystals by using
electron-positron density functional theory [2] with code PHASE [3]. We find that in the nonmagnetic
cases, the positron lifetimes in Fe, Ni, and Co, are 101.0ps, 99.3ps, and 96.6ps, respectively, which arecomparable with experimental ones (106ps, 110ps, and 118ps) [4]. In the magnetic cases, we find that thedifferences between lifetimes of minority and majority spins are 11.85ps, 3.752ps, and -4.365ps, for Fe,
Co, and Ni respectively. This negative value in Ni is consistent with experiment of three photon
polarization measurements (P3γ measurements) [5]. The origin of this negative value is expected to be thedelocalization of minority electron distribution in ferromagnets.
1. A.Kawasuso, M.Maekawa, Y.Fukaya, A.Yabuuchi, and I.Mochizuki:Phys.Rev.B 83, 100406(R) (2011)
2. A.Nakamoto, M.Saito, T.Yamasaki, M.Okamoto, T.Hamada, and T.Ohno: Jpn.J.Appl.Phys.47, 4(2008)2213
3. CISS: http://www.ciss.iis.u-tokyo.ac.jp/software/
4. H. Takenaka and D. J. Singh:Phys.Rev B 77, 155132(2008)
5. S.Berko and A.P.Mills, J.de.Phys, C 1(1971)287.

P-35

First-princile calculations of positron-attachedpolyatomic molecules
Y. Kita, T. Oyamada, and M. Tachikawa
Graduate School of Nanobioscience, Yokohama City University, Japan
E-mail: tachi@yokohama-cu.ac.jp
The positron, which is the anti-particle of the electron, is now widely used in both scientific andtechnological areas such as physics, chemistry, material science, medicine, and their interdisciplinary
areas. The detail mechanism of such processes, however, are still unclear in the molecular level. A
positron affinity (PA), which is a binding energy of a positron to an atom or molecule, is one of the mostimportant properties for studying positron attachment process. The PA values have now been
experimentally measured by Surko and co-workers for many molecular species such as somehydrocarbons, alcohols, and halogenated hydrocarbons [1]. Their PA measurement is based on thevibrational Feshbach resonance by incident low-energy positrons, in which the formation of a positronmolecular complex at the molecular vibrational excited states is suggested. Thus, in order to elucidate
the mechanism of the positron binding to molecules in vibrational excited states in detail, the theoreticalanalysis including the effect of the molecular vibrations is indispensable.
In this study, we developed a new theoretical method for analyzing the effect of molecularvibrations on positron affinities in order to elucidate the mechanism of the positron binding to moleculesin vibrational excited states. Our method is based on both the anharmonic vibrational state theory using
quantum Monte Carlo method [2] and ab inito multi-component molecular orbital theory [3,4] thatenable us to solve the electronic and positronic wave functions simultaneously. To demonstrate theeffect of molecular vibrations to the positron bindings with our method, we analyzed the characteristicfeatures of the positron binding to some small molecules such as hydrogen cyanide (HCN)[2],
formaldehyde (CH2O)[5] molecules, etc. We found that (i) for HCN molecule, the vibrational
excitations of the CN and CH stretching modes enhance the PA value compared to that of the vibrational
ground state, whereas the excitation of bending mode deenhances it, and (ii) for CH2O molecule, thevibrational excitations of the C=O stretching mode enhances the PA value, whereas the excitation of
CH2 rocking mode deenhances it. We confirmed that such PA variations arise from the change in both
permanent dipole moment and dipole-polarizability at each vibrational excited state.
We will discuss the role of electron-positron correlation for the binding of a positron to lithium
hydride (LiH) molecule in the presenation.
[1] Gribakin, G. F., Young, J. A., Surko, C. M., Rev. Mod. Phys. 82, 2557 (2010). [2] YK and MT, Eur.
Phys. J. D 68, 116 (2014). [3] MT, YK, R. J. Buenker, Phys. Chem. Chem. Phys. 13, 2701 (2011). [4]MT, YK, R. J. Buenker, New J. Phys. 14, 035004 (2012). [5] Y. Yurika, YK, MT, Phys. Rev. A 89,
062711 (2014).

P-36

DFT calculations for oxidation of SiC
T. Ono** Center for Computational Sciences, University of Tsukuba, Japan
E-mail: ono@ccs.tsukuba.ac.jp
Silicon carbide (SiC) is attracted much attention due to its excellent physical properties, such asa high thermal conductivity, high breakdown strength, and large band gap. However, unlike Si
MOSFETs, SiC MOSFETs suffer from unacceptably low carrier mobility. One of the origins for the low
carrier mobility is the generation of large amount of interface defects at SiC/SiO2 interface during dry
oxidation process. It is reported that the carrier mobility becomes larger when the interface defectdensity is reduced. The understanding and precise control of the atomic structure of SiC/SiO2 interface is
indispensable to increase the carrier mobility of SiC MOSFETs.
In this study, DFT calculations for the oxidation process of a 4H-SiC(0001) surface and 4HSiC(0001)/SiO2 interface are conducted to investigate the initial and middle stages of the oxidation,
respectively. I employ RSPACE code,1 which is based on the real-space finite-difference approach andprovides us with the ground-state atomic and electronic structures using a time-saving double-grid
technique. By sequentially inserting O atoms between Si-C bonds, I determine the most stable sites foreach O atom inserted into a Si-C bond. I found that the oxidation does not proceed in a layer-by-layermanner both on the SiC(0001) surface and at the SiC(0001)/SiO2 interface. O atoms enter the Si-C
bonds inside the substrate before the Si-C bonds in the upper layer are oxidized so that the increase in
the lattice constant mismatch between 4H-SiC(0001) and SiO2 is suppressed, which is different from theoxidation process of the Si(001)/SiO2 interface. Next, the energy gains of CO and CO2 emissions are
examined for each model by removing C and O atoms in the form of CO and CO2 molecules,
respectively. It is revealed that CO2 emission preferentially occurs in the initial stage of the oxidation
while CO emission becomes dominant as the oxidation proceeds. I conclude that there is significant
contribution of the interface stress owing to the lattice constant mismatch between 4H-SiC(0001) andSiO2 conributesplays in the removal of C.
1. K. Hirose, T. Ono, Y. Fujimoto, and S. Tsukamoto, First Principles Calculations in Real-SpaceFormalism, Electronic Configurations and Transport Properties of Nanostructures, (Imperial College,
London, 2005).

P-37

Theoretical analysis of Fe/Cu(001) ultrathin films bydensity functional theory
Y. Tatetsu*, S. Tsuneyuki*,** and Y. Gohda*,**** Department of Physics, The University of Tokyo, Japan
E-mail: tatetsu@cms.phys.s.u-tokyo.ac.jp** Institute for Solid State Physics, The University of Tokyo, Japan*** Department of Materials Science and Engineering, Tokyo Institute of Technology,
Japan
Magnetic thin films have been studied because of their interesting and peculiar magnetic behaviors
compared to their bulk systems. These behaviors can come from structural transitions depending on thetemperature and growth conditions. Fe/Cu(001) films are one of the most studied magnetic thin films forthe past decades, because of their complex magnetic structures.1,2) In these systems, the fcc or distorted
fcc Fe films have been epitaxially grown on a Cu(001) substrate even below room temperature, since thelattice parameters of Cu (3.615Å) and fcc Fe (3.58Å) are quite close to each other. Several theoretical
calculations have been also reported for the systems, but its ground state is controversial.3,4)
In order to understand the electronic and magnetic structures of the fcc-Fe/Cu(001) system, we
performed first-principles calculations using a computational code, OpenMX.5) Our structural model
consists of seven Cu layers and several Fe layers capped by a 10-Å vacuum layer. The structural
optimization is considered to calculate a realistic structure of this system. We adopted the generalized
gradient approximation, which can explain well the ground state and the lattice constant of ironcompared with the local density approximation.6) According to our collinear spin calculations, theground state is not the ferromagnetic structure but an antiferromagnetic structure in the 4-monolayer(ML) system from the total energy analysis of allowable spin configurations in our model structure. In
the 5 to 7-ML systems, antiferromagnetic structures are more stable than ferromagnetic structures,
which is in good agreement with experimental results. We also calculated the non-collinear spin
configuration, which considers the spin-orbit interaction. This calculation indicates that the spin-orbit
coupling in Fe sites can be ignored due to the weakness of the orbital moments of Fe. More detailed
magnetic structures will be discussed in the presentation.
1. H. Abe et al., Phys. Rev. B 77, 054409 (2008).
2. D. Pescia et al., Phys. Rev. Lett. 58, 2126 (1987).
3. R. Lorenz and J. Hafner, J. Magn. Magn. Mater. 157/158, 514 (1996).
4. D. Spišák and J. Hafner, Phys. Rev. B 64, 94418 (2001).
5. http://www.openmx-square.org
6. T. Asada and K. Terakura, Phys. Rev. B 46, 13599 (1992).

P-38

First-Principles Calculations on Electronic and Magnetic
Properties in Nanofacet on SiC(0001) Surface
K. Sawada, J. -I. Iwata and A. Oshiyama
Department of Applied Physics, The University of Tokyo, Japan
E-mail: sawada@comas.t.u-tokyo.ac.jp
The epitaxial growth of SiC films plays a central role in the fabrication of SiC power devices and thenanometer-scale facet (nanofacet) are periodically self-organized on the SiC(0001) surfaces which isslightly misoriented toward the [ 112n ] direction with the vicinal angle θ (θ = 0-8o)[1, 2]. The
transmission electron microscopy measurements reveal that such nanofacets consist of bunched atomic
steps[1, 2]. Surprisingly, the facet angle ϕ which is the angle between the (0001) and ( 112n ) planes ispredominantly in the range of 12-16 o[1, 2] and the height of the nanofacet along the (0001) direction isquantized to an integer or a half-integer of the unit-cell height[1-3].
Recently, we have clarified the mechanism of the nanofacet formation on SiC(0001) surfaces using
first-principles calculations based on the density functional theory[4]. We have found that the balance
between two factors, i.e., the step-step repulsive energy and the surface-energy variation, which comesfrom the different bilayer atomic sequence near the surface, is the reason for the constant facet angle andthe quantization of the facet height[4]. On the other hand, surface nanostructures may generate new andunexpected physical phenomena due to the novel atomic structures. Therefore, to investigate electronic
structures in the nanofacet on the SiC(0001) surface using first-principles approaches based on thequantum theory is important for fabrications of the nano-device with new function.
In this study, we perform first-principles electronic-structure calculations on the nanofacet formed on
the SiC(0001) surface. We find peculiar electronic states with dispersionless bands along the step edges(SEs) near the Fermi level and the electronic states are mostly localized at SE C atoms. To explore
possibilities of the observation of these peculiar states, we examine the situation that the nanofacet iscovered by H atoms and calculate the H-absorption energy at the several positions on the nanofacet. We
find that absorbed H atoms energetically prefer terraces to SEs and the H-absorption energy at a part of
SE C atoms is the lowest. Moreover, we reveal that the ferromagnetic chains induced by the flat-band
ferromagnetism appear at SEs on the H-terminated SiC(0001) surface except for the SE C atoms.
1 H. Nakagawa et al., Phys. Rev. Lett. 91, 226107 (2003).
2 M. Fujii et al., Phys. Rev. Lett. 99, 016102 (2007).
3 K. Arima et al., Appl. Phys. Lett. 90, 202106 (2007).
4 K. Sawada et al., Appl. Phys. Lett. 104, 051605 (2014).

P-39

Effect of SiC stacking on the electronic properties of
the SiC/SiO2 interface
Christopher Kirkham,1 Tomoya Ono2
1
Graduate School of Engineering, Osaka University, Osaka, Japanemail: kirkham@cp.prec.eng.osaka-u.ac.jp
2
Center for computational sciences, University of Tsukuba, Tsukuba, Japan
Silicon Carbide is a wide band-gap semiconductor material that can be used for electronic devices which
operate at high temperature and power, conditions under which Silicon fails. Like Si, the native oxide of
SiC is SiO2, but its use in practical devices has been hampered by the low channel mobility of the
SiC/SiO2 interface. The low mobility has been attributed to defects in the interfacial region, which havebeen the subject of prior studies [1][2] aimed at determining their effect, and how to eliminate them.
In this work we performed electronic structure calculations using the RSPACE [3] code to investigate
the effect of SiC stacking on the electronic properties of the SiC/SiO2 interface, both in the presence andabsence of defects. Measures such as the energies and Local Density of States (LDOS) of thesestructures were used as a means of comparison.
The interface was modelled using 4H-SiC and β-tridymite SiO2, allowing for 4 possible variations of theclean interface, based on the SiC stacking and the relative positions of the SiC and SiO2. Previously
known defects [1][2], such as excess C or O atoms, were then introduced into the interfacial region.

[1] P. Deak et al., J. Phys. D: Appl. Phys. 40, 6242–6253 (2007)[2] A. Gavrikov et al., J. Appl. Phys. 104, 093508 (2008)[3] Hirose K, Ono T, Fujimoto Y, Tsukamoto S: First-Principles Calculations in Real-Space Formalism.
London: Imperial College Press; 2005.

P-40

The role of surface reconstruction in determining the
growth path of the {105} facet of a Ge hut
S. Arapan*, D. Bowler** and T. Miyazaki** National Institute for Materials Science, Tsukuba, Japan
E-mail: sergiu.arapan@gmail.com** University College London, UK
Self-assembled nano-islands as a result of hetero-epitaxial growth have received considerable attention
due to their potential application in modern electronic devices.[1] One assumes that a Ge hut cluster
grows on a SiGe (001) substrate by adding new facets.[2] Various kinetic models of an island growthprovide a good description of experimental observations of a hut growth, but can not describe the actual
growth of a new facet layer.[3,4] Direct STM imaging of nano-islands lacks the microscopic picture of
the facet growth process and any direct evidence for the facet nucleation sites.
In this work we have studied the growth of a new {105} facet layer by performing linear scaling DFT
calculations on a realistic model of Ge hut cluster. Earlier DFT calculations have evidenced that thereconstruction of the (105) surface with formation of U shaped structures is responsible for the stabilityof Ge huts.[5,6] Our research reveals that the structure of this reconstructed (105) surface determines thegrowth path of a new {105} facet layer. By performing energy calculations of one-, two-, and threedimer structures we provide direct evidence of a top-to-bottom facet growth. This result is further
supported by calculating the stability of partial facet layers, thus we resolve the ambiguity of the {105}facet growth morphology.
1.

J.-N. Aqua, I. Berbezier, L. Favre. T. Frisch, and A. Ronda, Phys. Rep. 522, 59, 2013.

2.

D. E. Jesson, G. Chen, K. M. Chen, and S. J. Pennycook, Phys. Rev. Lett. 80, 5156 (1998).

3.

Martin Kästner and Bert Voigtländer, Phys. Rev. Lett. 82, 2745 (1999).

4.

Michael R. McKay, J. A. Venables, and Jeff Drucker, Phys. Rev. Lett. 101, 216104 (2008).

5.

Y. Fujikawa, K. Akiyama, T. Nagao, T. Sakurai, M. G. Lagally, T. Hashimoto, Y. Morikawa,
and K. Terakura, Phys. Rev. Lett. 88, 176101 (2002).

6.

P. Raiteri, D. B. Migas, Leo Miglio, A. Rastelli, and H. von Känel, Phys. Rev. Lett. 88, 256103(2002).

P-41

First-principles study of Rashba effect in artificial
superlattice (LaAlO3)n/(SrTiO3)nMiho Nishida*, Fumiyuli Ishii**, Hiroki Kotaka** and Mineo Saito*** Graduate School of Natural Science and Technology Kanazawa University, Japan
E-mail: m-nishida@cphys.s.kanaszawa-u.ac.jp** Faculty of Mathematics and Physics Institute of Science and Engineering
Kanazawa University, Japan
Recently, artificial superlattices are extensively studied for the application to the spintronics device. In
particular, heterostructures of perovskite-type transition-metal oxides attract attention because they
exhibit a variety of physical properties[1]. For examples, high-mobility electron gas[2] and tunable
Rashba-spin-splitting[3] caused by internal electric field in LaAlO3/SrTiO3 have been reported. These
interesting new properties may originate from the interface of the artificial superlattice. However, themicroscopic origin of the phenomenon and the atomic/electronic structure of these interfaces have notbeen understood sufficiently.
In this study, we clarify the electronic structure of artificial superlattice (LaAlO3)n/(SrTiO3)n by using
first-principles electronic structure calculations. Figure 1 shows band structures of (LaAlO3)n/(SrTiO3)n(n=2,4,6). The number of layers increases, the band gap becomes smaller. Finally, the band structure of(LaAlO3)6/(SrTiO3)6 has a metallic band structure. The all calculated band structures show the Rashba
splitting around the ! point. We also estimate the Rashba coefficient. The Rashba coefficients are 12-14
meVÅ. These calculated Rashba coefficients are in same order with experimental one (18 meVÅ)[3].

Figure 1. The band structures of (LaAlO3)n/(SrTiO3)n. (a) n=2, (b) n=4, (c) n=6. (d) The extended figureof Ti d-orbitals in (LaAlO3)6/(SrTiO3)6.
1.

H.Y. Hwang, Y. Iwasa, M. Kawasaki, B. Keimer et al., Nature Mater. 11,103 (2012).

2.

A. Ohtomo and Y. Hwang, Nature 427, 423 (2004).

3.

A.D. Caviglia M. Gabay, S. Gariglio, N. Reyren et al., Phys.Rev.Lett. 104, 126803 (2010).

P-42

Surface states of Bi (001) multi-layer nano film: spin
distribution in the real space and momentum space
H. Kotaka *, F. Ishii**, and M. Saito*** Institute of Science and Engineering, Kanazawa University, Japan
E-mail: kotaka@cphys.s.kanazawa-u.ac.jp** Faculty of Mathematics and Physics, Institute of Science and Engineering,
Kanazawa University, Japan
Bismuth has strong SOI caused by heavy atomic number. Nano-structures which is constructed by Biis suitable for examining the various phenomena caused by the SOI including the Rashba effect1-2. In
addition, Bi has the added advantage of high affinity for semiconductor surface and case of use3.
Recently, 3D-orientation pattern of spins at reciprocal lattice space have been observed on Bi (001)surface by spin-resolved angle-resolved photoemission spectroscopy (SR-ARPES)4.
We perform fully-relativistic first-principles study of Bismuth (111) multi-layer film, and discuss about
the surface-localization spin states in detail. Our research is intended to contribute to the elucidation ofphysical quantity originating in surface-localizated state at Bi (111) surface. We calculate surfacelocalizated spin ratio at Fermi surface, and illustrate Rashba spin texture in the Brillouin zone, andestimate Rashba cofficient of surface-state bands which is buried in the bulk state. Our calculated results
confirm the previous experimental SR-ARPES studies4.

1. I. E. Rashba: Sov. Phys. Solid. State. 2 (1960) 1109.
2. Y. M. Koroteev, G. Bihlmayer, J. E. Gayone, E. V. Chulkov, S. Blu ̈gel, P. M. Echenique, and P.
Hofmann: Phys. Rev. Lett. 93 (2004) 046403.
3. T. Nagao, J. T. Sadowski, M. Saito, S. Yaginuma, Y. Fujikawa, T. Kogure, T. Ohno, Y. Hasegawa,
S. Hasegawa, and T. Sakurai: Phys. Rev. Lett 93 (2004) 105501.
4. A. Takayama, T. Sato, S. Souma, and T. Takahashi: Phys. Rev. Lett. 106 (2011) 166401.

P-43
Stacking-faults and anti-phase boundary energies in
Ni3X (X = Si, Ga, Ge) alloys: An ab initio study
M. Rahaman,*,** S. Watanabe** and J. Iwata***Institute for Solid State Physics, The University of Tokyo, Japan**Graduate School of Engineering, The University of Tokyo, Japan
E-mail: Rahaman@cello.t.u-tokyo.ac.jp

We present the defects formation energies in Ni3 X (X = Si, Ga, Ge) alloys obtainedby the first-principles calculations based on RSDFT code within the real-spacedensity functional theory. RSDFT code is suitable for this study in the sense that
defects in materials require the use of large supercell, and that imposing periodic
boundary condition, which is mandatory in traditional plane wave method, is notnecessary in this code. We note that the stacking-fault energies (SFE) and anti-phaseboundary energies (APBE) are important parameters to determine the plastic
properties of Ni3X (X = Si, Ga, Ge) alloys.
We have found that the SFE and APBE obtained by the RSDFT code agree
satisfactorily with those reported in literatures and obtained by projector augmented
wave (PAW) method within supercell approach.
In addition, we have examined the temperature dependence of SFE and APBE in
Ni3X (X = Si, Ga, Ge) alloys using PAW method within supercell approach. The
effect of temperature on SFE and APBE is explored by considering in three steps: 1)
the one-electron thermal excitations in the electronic structure calculations, 2)temperature dependent lattice constant, and 3) vibrational free energy in the harmonic
approximations. Within the framework of the quasi-harmonic approximation,
thermodynamic properties of Ni3X (X = Si, Ga, Ge) alloys including the temperaturedependent lattice constant are determined. The results are in agreement with available
experimental data in a wide temperature range. It is found that the effects oftemperature on SFE and APBE are substantial in Ni3X (X = Si, Ga, Ge) alloys.

P-44

Ab-initio calculation of structure and electronic propertiesof a La0.75Ca0.25MnO3 surface
S. Nakamura*, Y. Ando*, E. Minamitani*, R. Shimizu**, K. Iwaya***, T. Ohsawa*,
T. Hitosugi**,***, S. Watanabe** Department of Materials Engineering, The University of Tokyo, Japan
E-mail: nakamura@cello.t.u-tokyo.ac.jp** Advanced Institute for Materials Research (AIMR), Tohoku University, Japan*** Institute of Physical and Chemical Research, Japan**** National Institute for Materials Science***** PRESTO, Japan Science and Technology Agency, Japan
Perovskite oxides (perovskites) have attracted considerable attention owing to a wide range ofapplications such as fuel cells, solar cells, and oxidation catalysts. Although the surface effect in theirfunctional properties may be significant, our understanding on perovskite-Mn oxides surface isinsufficient at all. The main reason for this lies in the difficulty in obtaining clean flat LaMnO3 surfaces.
Recently, we have succeeded in the epitaxial growth of La0.75Ca0.25MnO3 thin film and atomic-resolution
observation of the surface of the grown film by scanning tunneling microscope (STM). In order toclarify its structure and electronic properties, we carried out theoretical studies in the present work.
To take account of the strong Coulomb interaction among 3d electrons in Mn ions, we used local spin
density approximation (LSDA) + U method with the Vienna ab-initio simulation package. We adopted
three models of La6Ca2Mn8O24 four-layered slab with different dopant sites, whose compositions are thesame as the experiments. Considering that the thin film was grown on SrTiO3 (100) substrate in theexperiment, we fixed the lattice constants and atomic positions of the undermost layer to thosedetermined by experiments.
In the further analyses, we used the most stable doping model of 3
models in which the Ca dopants were positioned farthest from surface.
The simulated STM image (See Figure) shows the same zig-zag
tendency as the experimental results. This can be understood from thereconstruction from (1×1) to (√2×√2) periodic structure. The electronic
states are ferromagnetic and metallic both in bulk and in the central partof the slab. On the other hand, the slab surface is nearly insulating withlittle density of states near the Fermi level. This is consistent with the

Figure: LDOS at 1.5 eV

observed scanning tunneling spectroscopy results showing a bandgap

below the Fermi level ofaround the Fermi level.

the most stable model.

P-45

First-principles study of strain-induced topological phasetransitions in bismuth chalcogenides
T. Kato*, H. Kotaka* and F. Ishii*** Graduate School of Natural Science and Technology, Kanazawa University,
Kanazawa 920-1192, Japan
E-mail: tkato@cphys.s.kanazawa-u.ac.jp** Faculty of Mathematics and Physics, Institute of Science and Engineering,
Kanazawa Univrsity, Kanazawa 920-1192, Japan
A topological insulator (TI) is one of the materials which is expected to be applied in novel electronic
devices. Novel properties of topological insulators are spin-polarized transport and suppression of elastic
backscattering on its metallic surface. The surface states are predicted by Z2 invariants 𝜈! ; 𝜈! , 𝜈! , 𝜈! .
The four Z2 invariants 𝜈! ; 𝜈! , 𝜈! , 𝜈! are defined for three-dimensional systems with time-reversal
symmetry. When 𝜈! = 1, the TIs are called "strong TIs (STIs)". STIs have metallic surface states forevery directions. When 𝜈! = 0, and 𝜈! = 1    (𝑖 = 1, 2, 3), the TIs are called “weak TIs (WTIs)”. WTIs
have metallic surface states for some directions. When 𝜈! = 0 and 𝜈! = 0    (𝑖 = 1, 2, 3), it is a normal
insulator. Therefore every insulator can be classified into one of these three topologically different
phases. Bi2Se3 is known for a STI with Z2 invariants 1; 0,0,0 and has spin-polarized metallic states at(1,1,1) surface [1-3]. Spin-orbit interactions and crystal structure play a crucial role of realization of the
STI phases in Bi2Se3 [4].
In this study, we systematically perfomed first-principles calculations of Bi2X3 (X=Te, Se). Based on theparity analysis [5], we evaluated the Z2 invariants from first-principles calculations [6]. Topologicalphase diagrams in the space of the lattice parameters and internal parameters were revealed. We will
discuss topological phase transitions caused by lattice strain.

Moreover, to find the non-trivial

topological phases, we will propose the hypothetical materials Bi2S3 and Bi2O3.
1. H. Zhang, C.-X. Liu, X.-L. Qi, X. Dai, Z. Fang and S.-C. Zhang, Nat. Phys. 5, 438 (2009).
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. Hassan, Natture Phys. 5, 398 (2009).
3. T. Kato, H. Kotaka, F. Ishii, Proc. of the 3rd International Conf. on Molecular Simulation (2014).
4. J. Liu, Y. Xu, J. Wu, B.-L. Gu, S. B. Zhang and W. Duan, Acta Cryst. C70, 118 (2014).
5. L. Fu and C. L. Kane, Phys. Rev. B 76, 045302 (2007).
6. W. Feng, J. Wen, J. Zhou, D. Xiao and Y. Yao, Comput. Phys. Commun. 183, 1849 (2012).

P-46

Surface magnetism induced by interstitial impurities in
α-PbO
E.F. Arguelles1, S. Amino1, S. Aspera1, H. Nakanishi1 and H. Kasai1,2,3
1
Department of Applied Physics, Graduate School of Engineering, Osaka University,
Japan
2
Center for Atomic and Molecular Technologies, Osaka University, Japan
3
Center for Continuing Professional Development, Osaka University, Japan
E-mail: kasai@dyn.ap.eng.osaka-u.ac.jp
The eﬀects of transition metal (TM) atoms, Fe and Mn, and host atom, Pb introduced as interstitial
impurities on the structural and electronic properties of the layered α-PbO (001) surface have been
explored in this work using the ab-initio calculations, based on the density functional theory for possible
applications in spintronics. Since it has been proven that ferromagnetic signals in experiments are often
detected in thin films, grain boundaries and interfaces1),2), a 2x2, 3-layered surface slab model with 20 Åof vacuum space is used in this study, with impurity atoms placed in between surface layer and thesecond layer of the crystal.
The impurities are found to induce magnetism in the host crystal with magnetic moment values of 2.25
µB, 3.11 µB and 0.94 µB for Fe, Mn and Pb interstitials defects, respectively and highly localised for thecase of transition metals and dispersed for the case of host interstitial.
In the bonding process, the TM’s lower energy lying d states form overlaps with nearest neighbour
oxygen atoms with non-bonding d states situated near or at the Fermi level and are spin split. These spin
split orbitals induce spin polarisation of p impurity states of oxygen atoms in the subsurface whichshows the potential of α-PbO as a possible material for spin-injection devices that make use of spin
dependent transport. Furthermore, even in the absence of electrons, the Pb interstitial induces long range
magnetic effects in the crystal. On the other hand, following Hund’s rule, the remaining non-bonding p
states of the impurity atoms harbour unpaired electrons with parallel spins. This shows that introducing
even non-magnetic elements atom into α-PbO surface as interstitial defects can be sources of unpaired
electrons that ultimately leads to induced magnetisation of the system.
1.

M. Khalid, et. al., Phys. Rev. B, 81, 214414 (2010)2.

T. Dietl, et. al., Phys. Rev. B, 55, R3347 (1997)

P-47

Rotational Effects on the Dissociative Adsorption and
Abstraction Dynamics of O2/Al(111)
K. Shimizu*, W.A. Diño* and H. Kasai** Department of Applied Physics, Osaka University, Japan
E-mail: kasai@dyn.ap.eng.osaka-u.ac.jp
Oxidation is one of the most common chemical reaction. When it involves oxygen, the reaction
generally depends on the amount of oxygen in the air and the nature of the material which
undergoes oxidation. From a microscopic point of view, the dissociative adsorption of O2 on thesurface is considered as a first step to oxidation. Aluminum is often taken as a benchmark material
to study oxidation, due to its simple electronic structure and wide range of applications. For thecorresponding surface, however, the first step to oxidation is still a subject of active investigation.
Experiments [1–3] reported low, vibrationally assisted, no surface temperature dependent, initial
sticking of O2/Al(111) (indicative of direct, activated dissociation) and widely separated O
adsorbates (ca. 80 Å) at low coverages. On the other hand, theoretical studies employing density
functional theory (DFT) [4,5] found an absence of absolute energy barriers in almost all of theconfigurations considered, suggesting that some other process may be required to explain theexperimental findings [6,7], and that dynamical aspects and orientational dependence are
significantly lacking [8].
In this study, we have performed quantum dynamical calculations by solving the time-independent
Schrödinger equation for O2 dissociative adsorption on Al(111) based on the corresponding spinpolarized potential energy surface (PES) results. Our calculation results show that O2 has a strong
orientation dependence, and the molecular rotational motion plays a significant role on the
dissociative adsorption [8]. At the conference, we will present a more detailed discussion of themechanism behind the results.
1. H. Brune et al., Phys. Rev. Lett. 68 624 (1992).
2. L. Österlund et al., Phys. Rev. B 55 15452 (1997).
3. M. Kurahashi et al., Phys. Rev. Lett. 110 246102 (2013).
4. K. Honkala et al., Phys. Rev. Lett. 84 705 (2000).
5. Y. Yourdshahyan et al., Phys. Rev. B 65 075416 (2002).
6. J. Behler et al., Phys. Rev. B 77 115421 (2008).
7. F. Libisch et al., Phys. Rev. Lett. 109 198303 (2012).
8. K. Shimizu et al., J. Phys. Soc. Jpn. 82 113602 (2013).

P-48

Spin-orbit coupling on wurtzite ZnO (1010) surface: firstprinciples density functional study
Moh Adhib Ulil Absor*, Fumiyuki Ishii**, Hiroki Kotaka*, and Mineo Saito*** Graduate School of Natural Science and Technology, Kanazawa University, Japan
E-mail: adhib@cphys.s.kanazawa-u.ac.jp** Faculty of mathematics and Physics. Institute of science and engineering,
Kanazawa University, Japan
Recently, ZnO attracted much scientific interest because of its potential application to electronic devices.
One of the possible applications is spintronics devices because the spin polarization[1] and the long spinlife time[2] of the two dimensional electron gas have been observed. The strong circular photo galvanic
effect on ZnO epitaxial films has been observed, which indicates a strong spin-orbit splitting[3]. In ourprevious study, we confirmed the tunable Rashba effect on ZnO by introducing strain[4]. In this paper,
we study the spin-orbit coupling on the wurtzite ZnO (1010) surface by performing first-principles
density functional calculations within the generalized gradient approximation. We use the openMXcode[5]. We calculate spin texture whose energy is slightly lower than that of the valence band
maximum. We find the quasi-one dimensional orientaion of the spin textures. Thus, it is expected thatthe strongly enhanched of the spin relaxation time can be achieved through a persistent spin helix (PSH)
mechanism[6]. This findings open the new possibility in the study of wurtzite-based PSH systems.
1.

K. Han et. al., Appl. Phys. Lett. 100, 192105 (2012).

2.

Y. Kozuka et. al., Phys. Rev. B 87, 205411 (2013).

3.

Q. Zhang et. al., Appl. Phys. Lett. 97, 041907 (2010).

4.

M. A. U. Absor, H. Kotaka, F. Ishii, and M. Saito, Appl. Phys. Express 7, 053002 (2014).

5.

T. Ozaki, H. Kino, J. Yu, M. J. Han, N. Kobayashi, M. Ohfuti, F. Ishii, T. Ohwaki, H. Weng, M.
Toyoda, and K. Terakura: http://www.openmx-square.org/.

6.

B. A. Bernevig, J. Orenstein, and S. C. Zhang, Phys. Rev. Lett. 97, 236601 (2006).

P-49

Two-dimensional Valley Electrons and Excitons in 3R
MoS2 Multilayers
R. Akashi*, M. Ochi**, S. Bordács***, R. Suzuki****, R. Arita**, Y. Tokura**, andY. Iwasa***** Department of Physics, The University of Tokyo, Japan
E-mail: akashi@cms.phys.s.u-tokyo.ac.jp** RIKEN Center for Emergent Matter Science (CEMS), Japan*** Department of Physics, Budapest University of Technology and Economics,
Hungary**** Department of Applied Physics, The University of Tokyo, Japan
Atomically thin slabs of group-VI transition-metal dichalcogenides MX2 are attracting considerable
interest as a promising building block of nano electronics/optoelectronics devices. In particular, theirvalley-dependent spin/orbital polarization is a subject of extensive research for possible valleytronics. In
the monolayer systems, a direct band gap emerges at K (K’) points in the hexagonal Brillouin zone andthe valence top states exhibit large spin splitting due to spin-orbit coupling and broken inversion
symmetry. The electrons having valley-contrasted polarization have been proposed to be controllable
with spin- or orbital-sensitive probes [1,2].
More recently, there have been various studies on the stacking variety of multilayered MX2. Although
the majority of them are on centrosymmetric 2H stacking, some of the present authors have seeked fornovel physics in noncentrosymmetric 3R stacking and found that the net valley polarization is present
even in bulk [3]. In the present study, we further examine the stacking dependence of the valley
electronic states. We find unique two-dimensional (2D) confinement for valley electrons and excitons inmolybdenum disulfide MoS2 with 3R stacking [4]. We show that the valley states have no interlayer
hopping due to the symmetry of their Bloch functions. From measurements of reflectivity spectra withanalyses based on an anisotropic hydrogen atomic model, we derive that the hopping suppression resultsin 2D hydrogen-like exciton spectral series and in-plane confinement of exciton wavefunction. Our
results indicate that dimensional properties of the valley carriers can be controlled only by the stacking
geometry, which can be utilized in future valleytronics.
1, D. Xiao et al., Phys. Rev. Lett. 108, 196802 (2012)
2, Q. H. Wang et al., Nat. Nanotechnol. 7, 699 (2012), for a review.
3, R. Suzuki, M. Sakano, Y. Zhang, R. Akashi, et al., Nat. Nanotechnol. 9, 611 (2014)
4. R. Akashi, M. Ochi, S. Bordács, R. Suzuki, R. Arita, Y. Tokura, and Y. Iwasa, in preparation.

P-50

Hopping Selection Rule of Electrons in Stacked
Multilayers and Emergent Flat Band Dispersion
R. Akashi* and R. Arita*** Department of Physics, The University of Tokyo, Japan
E-mail: akashi@cms.phys.s.u-tokyo.ac.jp** RIKEN Center for Emergent Matter Science (CEMS), Japan
Symmetry of the system constrains possible transitions between quantum states. Such constraints arerobust against experimental complexities and so useful to predict various physical properties of thesystem. For example, optical selection rules predict which transitions are possible/impossible dependingon the orientation and polarization of incoming light. These predictions are confirmed byappearance/absense of peaks in observed spectra. In the present study, we address a selection rule for
hopping processes of electrons between layers in multilayered compounds [1], which governs generalelectronic properties.
In a separate presentation [2], we discuss the interlayer hopping in molybdenum disulfide with 3R
stacking. There, we prove that the 3R stacking geometry causes quantum interference and the interlayer
hopping processes of valence-top and conduction-bottom states at K and K’ points in the hexagonal
Brillouin zone are perfectly suppressed. In the present study, we generalize this hopping-suppressing
mechanism. We establish a theorem for any interlayer intraband hopping in any multilayered systems;
when two identical layers having a certain in-plane rotation/reflection symmetry are stacked with
nonzero in-plane shift, there are always k points in the Brillouin-zone boundary where interlayer
intraband hopping processes for nondegenerate Bloch states are exactly prohibited.
The above theorem is useful for searching for unique electronic properties of layered bulk materials due
to anomalously large effective mass with respect to certain directions or even flat band dispersion. We
reexamine some prototypical materials such as stacked boron nitrides and interpret their band structuresin view of the present hopping selection rule.

1, R. Akashi and R. Arita, in preparation.
2, R. Akashi, M. Ochi, S. Bordacs, R. Suzuki, R. Arita, Y. Tokura, and Y. Iwasa, “Two-dimensional
Valley Electrons and Excitons in 3R MoS2 Multilayers”, to be presented in ISC-QSD2014.

P-51

Electronic Structures and Stabilities of Defects and
Impurities in Hexagonal Boron-Nitride Atomistic Layers
Yoshitaka Fujimoto* and Susumu Saito*,**,**** Department of Physics, Tokyo Institute of Technology, Japan
E-mail: fujimoto@stat.phys.titech.ac.jp** International Research Center for Nanoscience and Quantum Physics,
Tokyo Institute of Technology, Japan*** Materials Research Center for Element Strategy, Tokyo Institute of Technology,
Japan
Since discovery of graphene, a two-dimensional monolayer sheet of hexagonal boron nitride (h-BN) has
attracted much attention from the viewpoints of fundamental nanophsyics and relevant applications in
nanoelectronics. Although graphene and h-BN sheet have similar geometrical properties, they exhibit
different electronic properties; graphene is a semimetal, whereas h-BN monolayer is a wide-gap
semiconductor. Therefore, the h-BN monolayers with the semiconducting properties are the promising
candidates for future nanoelectronics materials. Substitutional doping with foreign atoms often provides afirm route to modify the electronic properties such as band gap and electrical conductivity. Actually, thedoping with carbon into h-BN monolayer has been performed [1], and the electronic properties of h-BNmonolayers change from insulating property into metallic one [2]. However, our knowledge as to theelectronic properties and the stabilities of carbon defects in h-BN sheets is still limited at present.
In the present work, we perform thorough first-principles investigations that reveal effects ofcarbon doping on the electronic structures and the energetics of the monolayer [3,4] and the bilayer of theh-BN sheets. We show that the donor and acceptor-type states can be induced by the C atoms placed at B
and N sites, respectively. These impurity states are found to be relatively deep, and we therefore discuss
the possible methods to manipulate the ionization energies of the C-impurity induced states. It is also
revealed that the manipulation of the ionization energies could open the new conduction channels.
In addition, we will also discuss the energetics and the electronic properties of B and B3N vacancies
which have been already produced and observed experimentally.

1.

O. L. Krivnek, M. F. Chisholm, V. Nicolosi, T. J. Penycook et al., Nature 464, 571 (2010).

2.

X. Wei, M. S. Wang, Y. Bando, and D. Golberg, ACS Nano 5, 2916 (2011).

3.

Y. Fujimoto, T. Koretsune, and S. Saito, J. Ceram. Soc. Jpn. 122, 346 (2014).

4.

Y. Fujimoto, T. Koretsune, and S. Saito, JPS Conf. Proc. 1, 012066 (2014).

P-52

First-principles Calculation of the Free Energy of Silicon
Monovacancy
Sholihun and Mineo Saito
Graduate School of Natural Science and Technology, Kanazawa University, Japan
E-mail: sholihun@cphys.s.kanazawa-u.ac.jp
Defects in semiconductor have attracted wide attention because of their crucial eﬀects on various
properties of materials. Vacancies in silicon have been extensively studied theoretically andexperimentally [1-6]. We perform density-functional-theory large-scale-supercell calculations whichcontain up to 2744 atomic sites. We calculate formation energies which are tabulated in Table I andconfirm the convergence. The difference between the formation energies calculated from 2744 and 1728
atomic sites is very small (0.02 eV), thus, our calculated result is well converged. Our estimated value isin agreement with those of experimental values, 3.1 – 4.1 eV [3-6]. We find that the most stablegeometry has the D2d symmetry. We next calculate the vacancy concentration by considering vibrational
effect. We use the 216 site supercell in this calculation. The estimated value is 2.9 x 1015 cm-3 at 1500 K,
which is very close to the experimental values, 1014 – 1016 cm-3 [4,7].
Table I. The calculated formation energies of various supercell sizes consisting of N atomic sites.
N
k-point
Symmetry
Ef (eV)
64
8
D2d
3.48
216
8
D2d
3.52
512
8
D2d
3.50
1000
8
D2d
3.49
1728
1
D2d
3.47
2744
1
D2d
3.49
[1] F. Corsetti and A. A. Mostofi, Phys. Rev. B 84, 035209 (2011)[2] A. F. Wright, Phys. Rev. B 74, 165116 (2006)[3] G. Watkins and J. Corbett, Phys. Rev. 134, A1389 (1964).
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[5] Y. Shimizu, M. Uematsu, and K. M. Itoh, Phys. Rev. Lett. 98, 095901 (2007).
[6] N. Fukata, A. Kasuya, and M. Suezawa, Physica B 308-310, 11251128 (2001).
[7] P. M. Fahey, P.B. Griffin, and J.D. Plummer, Rev. Mod. Phys. 61, 289 (1989).

P-53

Relaxation effect of X-ray photoelectron spectroscopy
for defects in semiconductors: a first-principles study
J. Yamauchi and N. Matsushima
Faculty of Science and Technology, Keio University, Japan
E-mail: jy@rk.phys.keio.ac.jp
One of the principal difficulties to obtain the information on defects in a bluk is the weak experimental
signals due to their low concentration. Recently, X-ray photoelectron spectroscopy (XPS) measurements
for dopant defects in silicon (Si) using powerful synchrotron radiation facilities to compensate the low
concentration.[1] On the other hand, one of the theoretical difficulties to calculate the XPS binding
energies for the defects is the evaluation of the boundary condition, which should be the same for all thedefect models. We carefully evaluated the boundary condition and calculated the XPS binding energies
for some dopant defects in Si and SiC [2-4].
In terms of the analysis for the XPS, there is the picture that the XPS level reflects the local
potential around the atom. In contrast, there is the contrary picture that the relaxation effect takes a largerole in the XPS. To examine which picture is valid, we investigated the correlation between the local
potential and the XPS level. In Fig. 1, we show the result for the boron (B) defects in Si. If thecorrelation between the XPS level and the local potential is complete, the points are on the line. In thiscase , the correlation seems to be weak. In the presentation, other data will be discussed.
This work is supported by a Grant-in-Aid for Scientific Research (No. 22104006) from MEXT.
1. K. Tsutsui, et al., J. Appl. Phys. 104, 093709 (2008).
2. J. Yamauchi, Y. Yoshimoto, and Y. Suwa, Appl. Phys. Lett. 99, 191901 (2011).
3. N. Matsushima and J. Yamauchi, JPS Conf. Proc 1 012027 (2014).
4. H. Kishi, M. Miyazawa, N. Matsushima, and J. Yamauchi, AIP Conf. 1583 226 (2014).
Figure 1. B 1s XPS levels of B defects in Si as a1function of the averaged local potential.

XPS LEVEL (eV)The averaged local potential of the B atom issubstituted by the eigenvalue of B 1s. The energy

0

origins for the XPS level and the averaged local
potentials are those for the substitutional B. The-1straight line is an eye guide.
-1

0

1

AVERAGED LOCAL POTENTIAL (eV)P-54

Charge states of impurity hydrogen in rutile oxide
semiconductors MO2 (M=Si, Ge, Sn, Pb, Ti, Zr, Hf)
Kanako Yoshizawa1, Yoshiki Iwazaki2, Yoshihiro Gohda3, and Shinji Tsuneyuki1, 4
1
Institute for Solid State Physics, The University of Tokyo, Japan
E-mail: yoshiz-k@cms.phys.s.u-tokyo.ac.jp
2
Taiyo Yuden Co., Ltd., Japan
3
Dept. Mater. Sci. Eng., Tokyo Institute of Technology, Japan
4
Department of Physics, The University of Tokyo, Japan
Impurity hydrogen (H) with three charge states (H0, H+, H−) influences the electronic properties of host
semiconductors. Controlling the electrical conductivity is important for the electronic device
applications. We study H states in rutile oxide semiconductors MO2 (M=Si, Ge, Sn, Pb, Ti, Zr, Hf) byusing DFT-GGA. We examine the charge states with the use of Bader analysis [1] after the optimization.
The calculation results show different H states for each oxide semiconductor. SiO2 and HfO2 take threecharge states (H0, H+, H−), ZrO2 takes H+ and H−, and the others take H+ only. There is an impurity bandwithin the band gap in SiO2, ZrO2, and HfO2 with H0 or H−. We discuss the cause of the H states in thisposter by calculating the band gap, the effective Bohr radius, and the binding energy as shown in the
Figure. H− can be stable with a deep impurity level, when the band gap is wide such as SiO2, ZrO2, and
HfO2. As the binding becomes stronger, the effective Bohr radius becomes smaller accordingly
stabilizing also H0 in SiO2 and HfO2.

Table : Electron-proton binding energy versus (a) band gap and (b) effective Bohr radius in rutile oxide
semiconductors MO2 (M=Si, Ge, Sn, Pb, Ti, Zr, Hf) within DFT-GGA. The sphere size indicates thepossible charge states (small : H+, medium : H+, H−, large : H0, H+, H−).
1. R. F. W. Bader, Atoms in Molecules - A Quantum Theory (Oxford University Press, Oxford, 1990).

P-55

A DFT+U study on oxygen ion migration in strained Smdoped ceria
M. Alaydrus*, M. Sakaue* and H. Kasai*,**,**** Department of Precision Science and Technology and Applied Physics, Graduate
School of Engineering, Osaka University, Japan
E-mail: kasai@dyn.ap.eng.osaka-u.ac.jp** Center for Atomic and Molecular Technologies, Osaka University, Japan*** Center for Continuing Professional Development, Osaka University, Japan
Recent experiments on thin films and hetero-structures of ionically conducting oxides have indicatedenhancement of oxygen ion conduction typically ascribed to strain-related effects. We performed
density functional theory (DFT) calculations with Hubbard U correction to investigate the effects ofbiaxial lattice strain on the oxygen anion diffusivity in Sm-doped ceria (SDC). Here we found that the
migration barriers are strongly affected by the applied strain. The changes in the migration barriers canalmost be linearly correlated with cation-anion bond-lengths between the migrating oxygen and its
nearest neighbor cations (left figure). In this work, we reported various possible dopant configurations
for oxygen ion migrations at the vicinity of the oxygen vacancy. Our results indicate that the ionicmigration barriers can be lowered by both compressive (fixed volume) and tensile strains (relaxedvolume/adjusted c-lattice) as shown in the right figure. The insight gained from this study may enable us
to engineer and to improve oxygen ion migration in ceria-based solid electrolyte materials bycompression or tension of the lattice parameters.[1]Fig.1. (Left) lot of migration energy versus cation-Omig bond-length for various strain values. (Right)
Migration energies of strained SDC under two different circumtances, fixed volume and relaxed volume.
1. M. Alaydrus, M. Sakaue, S. M. Aspera, T. D. K. Wungu, N. H. Linh, T. P. T. Linh, H. Kasai, T.
Ishihara, and T. Mohri, J. Phys. Soc. Jpn., 83, 094707 (2014).

P-56

First-principles study of hydrogen-bonded molecular
conductor, κ-H3(Cat-EDT-TTF/ST)2
T. Tsumuraya1,2, H. Seo1,3, R. Kato1 and T. Miyazaki2
1
RIKEN, Japan
2
Computational Materials Science Unit, National Institute for Materials Science,Japan
3
CEMS, RIKEN , Japan
E-mail: tsumu@riken.jp
Proton dynamics in relatively short intermolecular hydrogen bonds play an essential role in various
functional molecular materials such as organic ferroelectrics and biochemical reactions. Recently, a newclass of hydrogen bonded molecular conductors has been synthesized; the compounds are based on
catechol with ethylenedithiote-tetrathiafulvalene, Cat-EDT-TTF and its diselena analog Cat-EDT-ST.
Among them, κ-type H3(Cat-EDT-TTF)2 is considered to be a dimer-type Mott insulator at ambientpressure and emerges as a candidate of realizing quantum spin liquid down to lowest temperature [1]. In
this crystal, two H(Cat-EDT-TTF) units share a hydrogen (H) atom with relatively short O-H-O hydrogenbonds, and its face-to-face dimers are formed in an anisotropic triangular lattice.
We study κ-H3(Cat-EDT-TTF/ST)2 by first-principles density functional theory (DFT) calculations [2].
To discuss a possibility of spin-frustration, inter-dimer hopping integrals are obtained by fitting to the
DFT bands. We find a quasi-one-dimensional anisotropy in the effective dimer-dimer interactions withfrustrated inter-chain couplings. Furthermore, the inter-layer hopping integrals are non-negligible
compared to the intra-layer couplings indicating their three-dimensionality of the electronic structure,owing to the absence of insulating layers. Furthermore, to understand role of the H atom in the hydrogenbonds, we calculate the potential energy surface for the shared H atom, and find a stable structure where
shared H atom is close to one of the O atoms; Charge disproportionation exists between the two H(CatEDT-TTF) units. This structure is energetically competitive to the experimental structure where the Hatom is located at the center of two O atoms. It is experimentally reported that a deuterium (D)substitution induces a charge disproportionation with the D localization [3]. We also discuss the structuraland electronic difference between our obtained structure and the experimental D-localized structure.
1.

T. Isono, H. Kamo, A. Ueda, K. Takahashi, M. Kimata, H. Tajima, S. Tsuchiya, T. Terashima, S.
Uji, and H. Mori, Phys. Rev. Lett. 112, 177201 (2014), and references therein.

2.

T. Tsumuraya, H. Seo, R. Kato, and T. Miyazaki, preprint arXiv; 1408:3162.

3.

A. Ueda, S. Yamada, T. Isono, H. Kamo, A. Nakao, R. Kumai, H. Nakao, Y. Murakami, K.
Yamamoto, Y. Nishio, and H. Mori, J. Am. Chem. Soc. 136 12184 (2014).

P-57

Ab-initio calculation for AC transport properties of single
molecule bridging between metallic electrodes
Y. Kawashiri * , D. Hirai * * , K. Sasaoka * * * , A. Tawara * , and S Watanabe **Graduate school of Engineering, The University of Tokyo, Tokyo, Japan
Email: kawasiri@cello.t.u-tokyo.ac.jp*****

Graduate school of Science, The University of Tokyo, Tokyo, Japan

Organization of Advanced Science and Technology, Kobe University, Kobe, Japan

Toward the realization of molecular electronics, it is necessary to understand theelectronic transport properties of single molecules. While stationary electronic transport
properties have been investigated by many scientists, non-stationary ones remain unclear.
They, however, are important when we design and control the dynamical operations ofmolecular electronics devices. In this study, we have carried out ab-initio calculation of
the AC transport properties of a molecular junction between metal electrodes.
We have used the method combining the density functional theory and thenonequilibrium Green’s function method with the linear response and wide-band limit
approximations [1]. One of our target systems is 1, 4-Benzenedithiol sand wiched
between semi-infinite one-dimensional gold electrodes (See inset in figure.). Based on
the fact that in low-frequency regime, admittance Y is expressed as 𝑌 ≃ 𝐺𝐷𝐷 + 𝑖𝑖ℏ𝜔,

where G D C , E, ℏ, and 𝜔 are DC conductance, emittance, Dirac constant, and frequencyof voltage, respectively. We have investigated correlations between emittance and otherphysical properties of the system.
Figure sho ws calculation results of emittanceand density of states (DOS) in scattering region
consisting of a bridging molecule and parts ofelectrodes. Our results revealed that there were
two types of correlations between emittance and
DOS depending on the Fermi level of system.
Furthermore, we found that these correlations
related to the magnitude of DC conductance. In

Figure: Calculated emittance and
DOS in the scattering region. Inset
is the calculation model.

the presentation, we will also sho w the results other systems (e.g. the same moleculewith graphene ribbon electrodes) to gain more insight of molecular bridging systems.
1. D. Hirai et al., J. Appl. Phys. 115, 174321 (2014).

P-58

Thermoelectric Property of Carbon Nanotube Buckypaper
Teppei Kato*, Shinji Usui** and Takahiro Yamamoto** Deptertment of Electrical Engineering, Tokyo Univ. of ScienceE-mail: 4313620@ed.tus.ac.jp** QuantumWise Japan*** Deptertment of Liberal Arts, Tokyo Univ. of Science
Enhancement of thermoelectric performance of materials is one of important tasks for solving thepresent energy and environment problems. Since Hicks and Dresselhaus proposed in 1993 that thethermoelectric performance of materials can be significantly increased by preparing them in the form of
one-dimensional nanowires [1]. A single-walled carbon nanotubes (SWNT) is a one-dimensional
material and expected to be a ubiquitous thermoelectric material with large thermoelectric power [1,2]. In
particular, a semiconducting SWNT buckypaper, which is a thin film consisting of semiconducting
SWNTs, is a potential candidate for new types of thermoelectric material. Recent experiments reported
that the temperature effects and doping dependence of Seebeck coefficient (thermoelectric power) of an
SWNT buckypaper is essentially different from those of an individual SWNT [3,4]. However, such
unusual behaviors of Seebeck coefficient of an SWNT buckypaper have not been understood yet.
We speculate that the above-mentioned unusual behavior
originates from the contacts between SWNTs. To clarify
the validity of this idea, we set a simulation modelFig 1. The laterally-contacted (8,0)
consisting of the laterally contacted SWNTs as shown in
Fig 1. As a typical example, the (8,0) semiconducting SWNTs are used in our simulations. The Seebeckcoefficient of the laterally contacted (8,0) SWNTs was calculated using the density functional theory
combined with Landauer theory [5,6]. We found that the laterally contacted SWNT has a large value ofthe order of 100 μV/K at room temperature [7]. This value is ten times larger than typical value ofSeebeck coefficient of individual SWNTs and is in agreement with experimental results. Anotherinteresting finding is that temperature dependence of Seebeck coefficient is sensitive to small change ofthe chemical potential. In the presentation, we will explain our simulation results based on Mott’s
formula of Seebeck coefficient and will show that these unusual behaviors originate from the resonant
tunneling at the contact between the SWNTs. We also show experimental measurements of Seebeckcoefficients of SWNT thin film, which is in excellent agreement with the simulation results. In addition,
we demonstrate the SWNT thermoelectric devices [7].
References[1] L. D. Hicks and M. S. Dresselhaus, Phys. Rev. B 47, 16631 (1993).
[2] Hone, et al., Phys. Rev. Lett. 80, 1042 (1998).
[3] Bradley, et al., Phys. Rev. Lett. 85, 4361 (2000).
[4] Baxendale, et al., Phys. Rev. B 61, 12705 (2000).
[5] See, for example, T. Kato, et al. Jpn. J. Appl. Phys. 52, 06GD05 (2013).
[6] http://quantumwise.co.jp/[7] Y. Nakai, et al., Appl., Phys. Express 7, 025103 (2014) .

P-59

Quantum Transport Simulation of Edge-Disordered
Graphene Nanoribbons
K.Takashima*, T,Yamamoto*** Department of Electrical Engineering, Tokyo University of Science, Japan** Department of Liberal Arts, Tokyo University of Science, Japan
E-mail:takahiro@rs.tus.ac.jp
Graphene is expected to be a channel material of field effect transistors (FETs) because of its highcarrier 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 to process it in the form of a nanometer width
ribbon, referred as graphene nanoribbons (GNRs). They have been successfully applied to FETs withhigh on-off ratio. A recent experiment reported that the resistance of GNRs increases exponentially with
their length even at the room temperature [1]. This non-Ohmic behavior is due to the edge-vacancy of
GNRs. The effects of edge-vacancy become more remarkable when the ribbon width becomes narrower
in the future. However the electronic transport properties of such narrow GNRs have not been clarified
yet.
In this study, we have computationally investigated the coherent electronic transport in edge-disorderedarmchair GNRs (ED-AGNRs) using the nonequilibrium Green’s function method combined with a tightbinding model. In our model, the edge-vacancy is modeled by removing pairs of carbon atoms at thearmchair-type edges. We calculated the conductance with various edge-disorder configurations withchanging the amount of edge carbon-pair vacancies from 4% to 50% and the ribbon-width from 0.74nm
to 2.95nm.
We confirmed that the averaged conductance of ED-AGNRs decreased exponentially with their lengths,
which is consistent with a previous experimental report [2]. We also examined (i) a relation between thelocalization length ξ and the edge-vacancy concentration, and (ii) the ribbon-width dependence of ξ. As
is expected, ξ increases with decreasing the edge-vacancy concentration and with increasing the ribbon
width. Furthermore, we found ξ for holes is longer than that for electrons, i.e., the electrons tend to be
more localized than holes. The electron-hole symmetry breaking on the localization will be discussed indetail.
References:[1] Xu et al., Nano Lett. 11, 1082 (2011).
[2] K. Takashima and T. Yamamoto., APL, 104, 093105 (2014).

P-60

Exciton many-body physics in carbon nanotubes
S. Konabe* and S. Okada** Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba,
Ibaraki 305-8571, Japanand Japan Science and Technology Agency, CREST, 5 Sanbancho, Chiyoda, Tokyo
102-0075, Japan
E-mail: konabe@comas.frsc.tsukuba.ac.jp
Interaction between light and matter in carbon nanotubes induces highly nonlinear excited-state
dynamics due to strong Coulomb interaction between electrons in the conduction and valence bands. It
has shown that strong excitonic effects prefoundly affect the optical properties in carbon nanotubes [1].
In addition to the single exciton problem, the exciton many-body problem plays a crucial role in opticalphysics of carbon nanotubes. In this presentation, we show our theoretical studies regarding the manybody physics (1) among excitons [2, 3] and (2) between excitons and doped carriers [4].
(1) Multiple-exciton generation (MEG) has attracted much attention as it drastically boosts thephotoelectric conversion efficiency since in a MEG process, light energy is converted to many (insteadof one) excitons. However, a detailed understanding of the microscopic mechanism for MEG has
remained unresolved. To investigate the origin of MEG, we developed a general theory of MEG using
quantum field theoretical methods that correctly include interaction effects between excitons andproposed a microscopic mechanism underlying MEG in carbon nanotubes [2]. Furthermore, ournumerical simulations suggest an extremely high photoelectric conversion efficiency in nanocarbon
materials [3].
(2) The optical properties of doped semiconductors are strongly influenced by elastic scattering
between excitons and charge carriers, determining the optically excited-state dynamics, and hence, e.g.,
the linewidths in the optical spectrum. In low dimensional materials such as carbon nanotubes, one
generally expects that this process is further enhanced due to strong Coulomb interaction. However, wefound that the scattering process is strongly suppressed, in contrast to conventional expectations. Further
investigation showed that this anomalous suppression arises from a novel excitonic property that is
specific to one-dimensional materials [4].
[1] V. Perebeinos et al. Phys. Rev. Lett. 92, 257402 (2004), C. D. Spataru et al. Phys. Rev. Lett. 92,
077402 (2004).
[2] S. Konabe and S. Okada, Phys. Rev. Lett. 108, 227401 (2012).
[3] S. Konabe and S. Okada, Appl. Phys. Lett. 104, 113110 (2013).
[4] S. Konabe, K. Matsuda, and S. Okada, Phys. Rev. Lett. 109,187403 (2012).

P-61

Electronic Properties of Graphene under an Electric Field
A. Yamanaka* and S. Okada*, *** Graduate School of Pure and Applied Sciences, University of Tsukuba, Japan
E-mail: ayamanaka@comas.frsc.tsukuba.ac.jp** JST CREST, Chiyoda-ku, Tokyo, Japan
In recent years, graphene is attracting much attention due to its possible application for semiconductor
electronic devices. In particular, graphene is regarded as the one of promising emerging materials for the
next generation semiconductor technology. Therefore it is urging us to unravel fundamental propertiesof graphene under an electric field for designing and fabricating graphene-based electronic devices. In
this work, we study the electronic properties of graphene under a parallel electric field to simulate theeffect of the electric field by source-drain electrodes in FET structure.
All calculations are performed by using the density
functional theory. To express the exchange correlation
potential among interacting electrons, we apply the local
density

approximation.

We

use

an

ultrasoft

pseudopotential to describe the interaction between
valence electrons and ions. The effective screening
medium (ESM) method is applied to investigate

Fig. 1. A structural model of nanoribbons
under the electric field.

behaviors of graphene under the electric field in theframework of the first-principles calculations.
We applied the electric field on the graphene
nanoribbons whose edges are terminated by H atoms inparallel direction as shown in Fig. 1. Under the external
electric field, we investigate the electrostatic potentialon each C atomic site to uncover how the electric field
affects on the electronic properties of graphene. In thecase of graphene nanoribbon with armchair edges, we

Fig. 2. Electrostatic potential at each C
atomic site of nanoribbons.

find that the potential modulation strongly depends on the atomic site. The fact indicates that the electricfield inside the nanoribbon is nonuniformly screened by the electrons on C atoms on the nanoribbons(Fig. 2). The structural analyses unravel that this unusual screening is ascribed to the bond alternation ingraphene nanoribbons[1]. Furthermore, we find unusual potential oscillation around the edge atomic
sites of graphene nanoribbons with zigzag edges due to the overscreening by the edge state.
1. A. Yamanaka and S. Okada, Jpn. J. Appl. Phys. 53 06JD05 (2014).

P-62

Electronic Structures of Two-dimensional sp2 Carbon
Networks of Fused Pentagon Trimers
M. Maruyama and S. Okada
Graduate School of Pure and Applied Sciences, University of Tsukuba, Japan
E-mail: mmaruyama@comas.frsc.tsukuba.ac.jp
Imperfections embedded into graphene networks occasionally lead to unsual electronic states near the
Fermi level. For example, graphene nanoribbons with zigzag edge show magnetic ordering at edge
atomic sites owing to the flat dispersion bands at the Fermi level arising from the delicate balanceamong the π electrons near the edges. In addition to the line defects (edges), topological defects, such aspentagons and heptagons in hexagonal network, also induces peculiar electronic structures; carbon
nanotubes with topological line defects show magnetic ordering along the line defects as in the case of
the graphene nanoribbon with zigzag edges. Therefore, sp2 carbon networks with topological defects are
expected to exhibits unusual physical properteis. In this work, we study the geometric and electronic
2

structures of sp carbon sheets which consist of fused of pentagon trimers (acepentalene structure) basedon the density functional theory with the local spin density approximation and the ultrasoft
pseudopotential.
Figure 1 shows optimized structures of sp2 carbon networks consisting of fused pentagon
networks trimers. We find that all sheets are metals. Furthermore, two of three sheets [Figs.1(a) and
1(b)] have flat dispersion
band in a part of Burilluinzone at the Fermi level
leading

to

the

spin

polarization on the sheet.
The

polarized

electron

spins

are

ferromagnetically aligned
and extended through the
sheet

with

the

spin

moment of 0.62 and 0.20

Fig.1 Geometric structures of fuesed pentagons netowrks.

µB/nm2 for the sheet (a) and (b), repsectively.
M. Maruyama and S. Okada: Applid. Phys. Express 6, 095101 (2013).
M. Maruyama and S. Okada: Jpn. J. Appl. Phys. 53, 06JD02 (2014).

P-63

Atomic and Electronic Structure Calculations for
Twisted Bilayer of h-BN sheets
K. Uchida, J.-I. Iwata and A. Oshiyama
Department of Applied Physics, The University of Tokyo, Japan
E-mail: kuchida@ap.t.u-tokyo.ac.jp

Atomic and electronic strucures of twisted bilayer h-BN sheets have been explored by our firstprinciples total-energy electronic-structure calculations for a series of twist angles θ. We have found that
the Moiré patterns in the atomic arrangements induce corrugations in the layers, and also a substantialchanges in the band structures and wave functions.
The results show that properties of h-BN sheets are not symmetric with respect θ = 30° [see Fig. (a)(c)], which is in contrast with the symmetric behavior of the corresponding properties in twisted bilayer
graphenes [1] with respect θ = 30°. The non-symmetric behavior is ascribed to a qualitative difference inthe stacking pattern between the structures with θ ~ 0° and those with θ ~ 60° in the twisted bilayer hBN sheets: For θ ~ 0°, the Moiré patterns in twisted bilayer h-BN sheets are composed of two local
patterns named AB and AA [Fig. (a)]; while for θ ~ 60°, the Moiré patterns are composed of three local
patterns named ABb, AA’, and ABn [Fig. (b)]. This qualitative difference does not exist in twisted
bilayer graphene because the A-site and B-site atoms are the same in graphene, showing that the nonsymmetric properties of the Moiré in twisted bilayer h-BN sheets are ascibed to the different A-site atom(B) and B-site atom (N).

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K. Uchida, S. Furuya, J.-I. Iwata, and A. Oshiyama, Phys. Rev. B (in press).

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P-64

Electronic properties and stacking geometries ofbilayer silicene
Y. Sakai and A. Oshiyama
Department of Applied Physics, The University of Tokyo, Japan
E-mail: y-sakai@comas.t.u-tokyo.ac.jp
Two-dimensional monolayer materials have attracted much interest ever since the first demonstration of
the experimental synthesis of graphene.[1] Monolayer of silicon (silicene) has been also experimentally
fabricated on Ag(111), ZrB2(0001), and Ir(111) surfaces recently.[2-5] The interlayer interaction of twomonolayer graphene (i. e. bilayer graphene) is of interest since it exhibits various interesting physicalproperties.[6-7] Therefore, the interlayer interaction of two silicene layers should be also of importance.
In this work, we systematically study the structural and electronic properties of freestanding bilayer
silicene within the framework of the density functional theory. Freestanding bilayer silicene is found tohave a number of local minima of the total energy with respect to the in-plane lattice constant. The local
minima correspond to various stacking geometries, but we find six thermodynamically stable stacking
geometries of freestanding bilayer silicene based on phonon dispersion relations obtained with thedensity functional perturbation theory. The interlayer bond lengths of these structures are shorter than
2.5 Å, indicating the covalent-like bonding between two silicene layers. Four of the six structures aredescribed by the 1×1 unit cell (4 silicon atoms in the cell) whereas the other two structures are describedby a 2×2 supercell. We also find an order of the total energies of these six structures, and the structureswith a 2×2 supercell have relatively lower total energies than the 1×1 structures. These low-energy
structures are found to have silicon-silicon bond lengths closer to the sp3 bond length of the bulk silicon.
The six structures exhibit semimetallic or semiconducting electronic properties depending on theirstacking geometries.
1. K. S. Novoselov et al., Science 306, 666 (2004).
2. P. Vogt et al., Phys. Rev. Lett. 108, 155501 (2012).
3. P. Vogt et al., Appl. Phys. Lett. 104, 021602 (2014).
4. A. Fleurence et al., Phys. Rev. Lett. 108, 245501 (2012).
5. L. Meng et al., Nano Lett. 13, 685 (2013).
6. T. Ohta et al., Science 313, 951 (2006).
7. A. Lucian et al., Phys. Rev. Lett. 106, 126802 (2011).

P-65

First-principles calculation of high-temperature phonon:
Applications to cubic SrTiO3
T. Tadano and S. Tsuneyuki
Department of Physics, The University of Tokyo, Japan
E-mail: tadano@cms.phys.s.u-tokyo.ac.jp
Phonon calculations are essential to evaluate thermodynamic functions, thermal expansion, electronphonon coupling strength, lattice thermal conductivity, and so forth. However, calculating phonons athigh temperatures or severe anharmonic systems such as ferroelectric materials are currently limited dueto the absence of anharmonic effects in the standard methods (DFPT and frozen-phonon). For example,
standard phonon calculations of cubic perovskites yield imaginary modes, which is a long-standing issue
that prohibits us to obtain thermodynamic functions and other vibrational quantities of paraelectricphases. To overcome the issue, anharmonic effects should be considered beyond the quasiharmonic
approximation.
In this study, we develop two different methods to calculate high-temperature phonons of severe
anharmonic crystals. One is based on the self-consistent harmonic approximation (SCHA) [1, 2] and theother is the molecular dynamics (MD) method [3, 4]. In the SCHA method, phonon frequencies are
renormalized by the quartic anharmonicity. Here, not only harmonic force constants (FCs) but also
quartic FCs are necessary, for which we employ thesupercell method [4]. In the MD method, harmonic FCs
are optimized along the trajectory of a first-principles
MD at high temperature. We applied these methods to
cubic SrTiO3, a high-temperature phase, and observedthat both methods can describe the hardening of softmodes (Fig. 1). As clearly seen in the figure, thecalculated phonon dispersion at 300 K is free fromimaginary modes, and agreements with experimental
results are quite satisfactory. In addition, phonon
linewidths and the lattice thermal conductivity of theparaelectric phase can be estimated by our approach.

Figure 1: Harmonic (dotted) and anharmonic(solid) phonon dispersion of cubic SrTiO3.
Anharmonic phonon frequencies are obtainedby the MD method at 300 K. Open symbols aremeasured values at room temperature (Ref. 5).

1. T. R. Koehler, Phys. Rev. Lett. 17, 89 (1966).
2. I. Errea, B. Rousseau, and A. Bergara, Phys. Rev. Lett. 106, 165501 (2011).
3. O. Hellman, I. A. Abrikosov, and S. I. Simak, Phys. Rev. B 84, 180301 (2011).
4. T. Tadano, Y. Gohda, and S. Tsuneyuki, J. Phys.: Condens. Matter 26, 225402 (2014).
5. W. G. Stirling, Journal of Physics C: Solid State Physics 5, 2711 (1972).

P-66

First-principles calculation of elastic constantsfor metallic hydrides under high-pressure
M. Geshi
Institute for NanoScienc, Design, Osaka University, Japan
E-mail: geshi@insd.osaka-u.ac.jp
In general, it is difficult to identify positions of hydrogen and its quantity in a unit cell fromexperiments except for neutron diffraction measurement. In high pressure experiments, we are interested
in a relation between positions of hydrogen or its quantity and physical properties. First-principles
calculations can determine atomic positions of hydrogen in crystal by performing relaxation of atomic
positions. To compare with the experimental observable quantity except for neutron diffraction
measuremen, we perform the calculation of elastic constants. We can compare the calculated elastic
constants with an experimentally determined ones using the Brillouin scattering measurement.
In this study, we have calculated elastic constants for several metallic hydrides assuming the CaF2
structure (Fm-3m) which is one of the typical structure of metallic hydrides. Systematically being
calculated the elastic constants as a function of the hydrogen concentration, we can show the possible
concentration of hydrogen for the CaF2 structure for each pressure.
We have used the Quantum-Espresso code[1] to perform calculation of elastic constants, relaxation ofcells and atomic positions, and phonon calculation with urtrasoft pseudopotentials and a GGA exchangecorrelation potential. In order to analyze the electronic structure more accurately, we have used WIEN2k
code[2]. The method to calculate the elastic constants is followed by our previous work.[3]For AH2+δ, (A=Y, La, Ti, Zr, V, Nb, and Ta), we have performed the calculation of elastic constants inthe pressure range from 0 to 50 GPa with adding δ from -1 to 1. When we increase δ, we add hydrogenat 4b site(1/2, 1/2, 1/2) one by one. When we decrease δ, we remove it from 8c site(1/4, 1/4, 1/4; 3/4, 3/4,
3/4) one by one. In these materials, the elastic constant C11-C12 is an important quantity to consider themechanical stability of the CaF2 structure. This is related to the electronic structure of AH2+δ.We willshow the typical results and give discussion about the physical origin.
1.S.Baroni,A.D.Corso,S.deGironcoli,P.Giannozzi,C.Cavazzoni,G.Ballabio,S.Scandolo,G.Chiarotti,P.Foc
her,A.Pasquarello,et al., http://www.pwscf. org/.
2. P. Blaha, K. Schwarz, G.K.H. Madsen, D. Kvasnicka, J. Luitz, WIEN2k, An Augmented
PlaneWave+Local Orbitals Program for Calculating Crystal Properties, Karlheinz Schwarz, Techn.
Universit ¨at Wien, Austria, 2001, ISBN 3-9501031-1-2.
3. M. Geshi, Physica B405, 517(2010).

P-67

Development of a first-principles model with long-range
interactions for ferroelectrics
T. Nishimoto1, T. Tadano1, Y. Gohda2, and S. Tsuneyuki1,3
1
Department of Physics, The University of Tokyo, Japan
E-mail: nishimoto@cms.phys.s.u-tokyo.ac.jp
2
Department of Materials Science and Engineering, Tokyo Institute of Technology,
Japan
3Institute for Solid State Physics, The University of Tokyo, JapanThe computational estimation of ferroelectric transition temperature (TC) is desired for finding
efficient ferroelectric materials. Since a typical first-principles molecular dynamics (MD) simulation
method is not computationally feasible when applied to the ferroelectric transition, a first-principles
model potential has been developed [1]. In this model, the potential energy is expressed as a function of
normal coordinates and strain selected for describing ferroelectric transition in perovskite oxides. Monte
Carlo [1] and MD [2] simulations based on this model succeeded in observing successive phasetransitions of BaTiO3. However, this approach cannot be applied to newly found organic ferroelectrics,
diisopropylammonium bromide (DIPAB) [3] since this model is specialized for the perovskite structure.
In this study, we develop a more general model for ferroelectrics. Our model is based on a firstprinciples anharmonic lattice model [4], which succeeds in20

calculating the thermal conductivity, and can be applied to aof atoms. We also explicitly consider Coulomb interaction due

Frequency (THz)16variety of materials by explicitly dealing with all coordinates

128

to site ionicity expressed by the dielectric tensor and the Born

4

effective charge tensors. The short-range interatomic force0

Experiment [5]Previous work
This workΓ

constants are estimated from first principles avoiding the
double counting of Coulombic contributions. We observed
dispersion of ionic crystals (Fig. 1). In addition, our model
showed that the Coulomb interaction causes structural
instability in the potential energy surface of ferroelectrics (Fig.
2). We expect that the MD simulation based on our model

X

Γ

L

X

W

L

First-principle
Harmonic
Quartic
Coulomb
Total (model)

10Energy per unit cell (meV)that our model can describe the LO-TO splitting in the phonon

K

Fig. 1: Phonon dispersion of MgO.

5

0

-5

-10
-0.06

enables us to estimate TC of a variety of ferroelectrics.

-0.04

-0.02
0
0.02
Amplitude of an eigen-vector

0.04

0.06

Fig. 2: Potential energy surface of BaTiO3.

[1] W. Zhong et al., Phys. Rev. Lett. 73, 1861 (1994), [2] T. Nishimatsu et al., Phys. Rev. B 78, 104104(2008), [3] D. Fu et al., Science 339, 425 (2013), [4] T. Tadano et al., J. Phys.: Condens. Matter 26,
225402 (2014), [5] M. J. L. Sangster et al., J. Phys.: C 3, 1026 (1970)

P-68

Ferroelectric tuning of spin-orbit fieldin ATiO3(A=Sr,Ba, and Pb)
F. Ishii*, and H. Kotaka**, T. Ohnishi**, M. Nishida**, M. Saito** Faculty of Mathematics and Physics, Institute of Science and Engineering,
Kanazawa University, Japan
E-mail: ishii@cphys.s.kanazawa-u.ac.jp** Graduate School of Natural Science and Engineering, Kanazawa University, Japan
Ferroelectrics are materials which possess spontaneous electric polarization associatedwith structural phase transition. The electric polarization in ferroelectrics can be controlled byexternal electric field and pressure. This electrical feature is applicable to several kind ofelectronic device such as nonvolatile ferroelectric memory. The ferroelectrics are also potential
candidate for spintronics application such as spin field-effect-transistor (spin-FET) made ofmetal-oxide-semiconductor [1]. In conventional spin-FET, the spin is controlled by the Rashba
effect caused by the external electric field [2]. By using the ferroelectrics for spin-FET, thespin can be controlled by electric polarization.
In this study, we have investigated spin state of ferroelectric bulk, film, and suplerlatticeof ATiO3(A=Sr, Ba, Pb). We have performed the fully-relativistic first-principles calculations
based on the non-collinear spin density functional theory implemented in OpenMX code[3].
By tuning the magnitude and direction of the electric polarization, spin-orbit coupling constantand the spin textures in the Bloch-wave vector space (momentum space) drastically changed,i.e., spin-orbit field is controlled by electric polarization. Based on the group theory, we
discuss the relation between the symmetry of crystal structures and spin textures. In contrast to
two-dimensional electron gas (2DEG) in the III-V semiconductor quantum well, the spin-orbit
coupling coefficients is large and thus the short spin wavelength of spin helix less than 100 nm
can be achieved.
1. S. Datta and B. Das, Appl. Phys. Lett. 56, 665 (1990).
2. E. I. Rashba, Sov. Phys. - Solid State 2, 1109 (1960).
3. T. Ozaki, et al., http://www.openmx-square.org/

P-69

Theoretical Analysis of Magnetic Properties of ε-Fe2O3
D. Hirai1, S. Tsuneyuki1,2, and Y. Gohda1,3
1
Department of Physics, The University of Tokyo, Japan
E-mail: hirai@cms.phys.s.u-tokyo.ac.jp
2
Institute for Solid State Physics, The University of Tokyo, Japan3
Department of Materials Science and Engineering, Tokyo Tech, Japan
Recent developments of chemical synthesis have enabled us to make ε-Fe2O3 in the form of ananoparticle, showing the largest coercivity among all the metallic oxides [1,2]. Therefore, it is expectedthat a superparamagnetic limit can be overcome using this material. However, the origin of highcoercivity remains unclear. To understand this mechanism is crucial not only for basic sicence, but also
for designing novel hard magnetic materials.
In this study, we performed first-principles simulations to understand the magnetic properties of εFe2O3, on the basis of density functional theory. We used the OpenMX code [3] to calculate theelectronic structure. First, we found that zero magnetization appears in pristine ε-Fe2O3. This is incontrat to finite magnetization observed in several experiments, where the values of magnetization are 36 emu/g [1,2]. We also caluculated the magnetocrystalline anisotropy energy (MAE) based on secondorder perturbation theory for spin-orbit interaction [4]. The calculated MAE is 71.5 kJ/m3, which issmaller than experimental values of 200-500 kJ/m3 [5].
Next, we examined the effect of an oxygen vacancy on the magnetic properties. It is shown that the
introduction of a specific vacancy site among six nonequivalent oxygen sites leads to finite
magnetization with the value of 2 emu/g when a single oxygen vacancy is introduced per unit cell. This
structure is the most stable among six possible structures and the formation energy are 3.26 eV. The
MAE is 352 kJ/m3, which is about 5 times larger that that of the pristine case. To clarify this MAE
enhancement, we decomposed the MAE into each Fe site and orbital. As a result, we found a large
contribution from the nearest Fe site from the vacancy site, which is absent in the pristine case. We also
elucidated that the spin-orbit interaction between occupied dx2-y2↓ and unoccupied dxy↓ significantly
increases the MAE due to the introduction of the oxygen vacancy. We will give more details in thepresentation.
1. S. Sakurai et al., J. Am. Chem. Soc. 131, 18299 (2009).
2. S.-I. Ohkoshi et al., Bull. Chem. Soc. Jpn. 86, 897 (2013).
3. www.openmx-square.org
4. Z. Torbatian et al., Appl. Phys. Lett. 104, 242403 (2014).
5. J. Tucek et al., Chem. Mater. 22, 6491 (2010).

P-70

Magnetic hardening induced bynonmagnetic organic molecules
M. Callsen*,**, V. Caciuc**, N. Atodiresei**, N. Kiselev** and S. Blügel*** Global Research Center for Environment and Energy based on Nanomaterials
Science (GREEN), National Institute for Materials Science,
1-1 Namiki, Tsukuba 305-0044, Japan
E-mail: CALLSEN.Martin@nims.go.jp** Peter Grünberg Institut (PGI-1) and Institute for Advanced Simulation (IAS-1),
Forschungszentrum Jülich, 52425 Jülich, Germany
To design new, molecule based magnetic materials with predefined magnetic and electronic properties is
one of the targets of single-molecule spintronics. By means of ab initio calculations in the framework ofdensity functional theory, we have revealed that the adsorption of a nonmagnetic π-conjugated organic
molecule on a ferromagnetic surface locally increases the strength of the magnetic exchange interaction
between the magnetic atoms binding directly to the molecule [1]. In particular, we investigated theprototypical, biplanar [2,2]paracyclophane molecule adsorbed on the Fe/W(110) surface. The observed
magnetic hardening effect leads to the creation of a local molecule mediated magnetic unit with a stable
magnetization direction and an enhanced barrier for the magnetization switching. In addition, this hybridorganic-ferromagnetic system exhibits a spin-filter functionality with sharp spin-split molecular-likeelectronic features at the molecular site.
1. M. Callsen, V. Caciuc, N. Kiselev, N. Atodiresei, and S. Blügel, Phys. Rev. Lett. 111, 106805 (2013).

P-71

Circular polarization in Eu, Mg, and O codoped GaN
A. Masago*, T. Fukushima*, K. Sato** and H. Katayama-Yoshida** Graduate School of Engineering Science, Osaka University, Japan
E-mail: masago@aquarius.mp.es.osaka-u.ac.jp** Graduate School of Engineering, Osaka University, Japan
We study electronic structures of a luminescent center that we proposed in our previous works toward
the high efficiency using VASP, a Vienna ab-initio simulation package. [1] The luminescent center isgenerated by the spontaneous spinodal nano-decomposition of impurities that are Eu, Mg, and O. The
electronic structure provides us with expectations of the circularly polarized luminescence.
The circularly polarized luminescence has much attention, because it is used in not only scientificobservations but also entertainment and medical tools such as three-dimensional display. Moreover, it isexpected to be applications in quantum computing, spintronics, and biological probe. However, thecurrent sources of the circularly polarized light need large, complex, or extra constructions like crystal
retarder, the spin-injection method, and inorganic LEDs. If we replace them with inorganic LEDs, we
can build such instruments with simpler constructions. Herein, Eu-doped GaN that is one of the
inorganic LEDs is a promising material for normal LEDs. The Eu-doped GaN has been synthesize as
red LEDs toward development of monolithic full-color LEDs, which work under seamless operating
conditions, because blue and green LEDs have been already synthesized by rare-earth-doped GaN. [2]
In order to enhance the luminescent efficiency of the Eu-doped GaN, we proposed an efficientluminescent center from a standpoint of the computational nano-material design. [3, 4] In the papers,
we described that the luminescent center was generated by codoping Eu along with a self-compensatedpair of the Mg acceptor and the O donor into GaN. These impurities simultaneously formed chain-likenano-structures such as Eu-O-Mg-N-Eu in the host due to the spinodal nano-decomposition.
In the present study, we show that an exchange interaction between the f-states of Eu and the p-statesof N and O occurs around these chain structures. Since it is similar to Zener's p-d exchange interaction,
we call it Zener's p-f exchange interaction.

The electronic states generated by the p-f exchangeinteraction are suitable for the circular polarization and finite total magnetic moments. Based upon thesefactors, we guess that the electronic and magnetic properties may be useful to prolong or control the
lifetime, color and intensity of the LEDs.
1. G. Kresse and D. Joubert, Phys. Rev. B 59 (1999) 1758.
2. D. Lee, A. Nishikawa, Y. Terai, and Y. Fujiwara, Appl. Phys. Lett. 100 (2012) 171904.
3. A. Masago, T. Fukushima, K. Sato, and H. Katayama-Yoshida, Jpn. J. Appl. Phys. 53 (2014) 061001.
4. A. Masago, T. Fukushima, K. Sato, and H. Katayama-Yoshida, Appl. Phys. Express 7 (2014) 071005.

P-72

Interaction between different kinds of transition-metalelements in quaternary magnetic semiconductors
T. Domon, Y. Sugimura, K. Kanazawa, R. Akiyama, S. Kuroda
Institute of Materials Science, University of Tsukuba, Tsukuba, Japan
E-mail: kuroda@ims.tsukuba.ac.jp
In the search for high-temperature ferromagnetic semiconductors, diluted magnetic semiconductors(DMSs) containing various kinds of magnetic elements have been studied. So far, ternary compounds
containing only one kind of magnetic element have been mainly studied, while quaternary compounds
containing two kinds of magnetic element have rarely been investigated. In quaternary DMSs, however,a robust magnetic ordering might possibly be realized due to the interaction between different kinds ofmagnetic element. In particular, in a special combination of transition-metal (TM) elements, such as Cr
and Fe in II-VI compounds, it was theoretically predicted[1] that the two kinds of TM elements arecoupled antiferromagnetically and a half-metallic electronic state is realized. In the present study, we
have investigated magnetic properties of a quaternary DMS in which Cr and Fe are incorporated in ZnTe.
We grew thin films of (Zn,Cr,Fe)Te on a GaAs substrate by molecular beam expitaxy (MBE). We
prepared a series of films with a fixed Cr composition around 6% and varied Fe composition ranging
from 0 to 2%. The measurement of magnetization for the series of grown films using superconducting
quantum interference device (SQUID) reveals that the coercive force increases with the increase of Fe
composition while the saturation magnetization decreases. These observations are seemingly consistent
with the theoretical prediction that the magnetic moments of Cr and Fe are coupled in an
antiferromagnetic way.
1. H. Akai, M. Ogura, PRL 97, 026401 (2006).

P-73

First-principles study of multipole ordered states
M.-T. Suzuki** RIKEN, Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198,
Japan
E-mail: michito.suzuki@riken.jp
Recently, f electron materials have drawn considerable interest, stimulated by observations of
intriguingly ordered ground states forming at low temperatures. A striking example is the formation of themultipole order (MPO), in which the order parameter is consist of the coupled spin-orbit. While recent
findings of MPO in the f -electron compounds promise to exotic materials with unprecedented functions,the complex constitution of the microscopic quantum states makes it difficult to identify the orderedstates experimentally. We have developed the first-principles method for the MPO states based on the
LDA+U formalism for the purpose of revealing the electronic property hidden behind the complex orbital
order.
First, we applied the method to the 3q-highrank magnetic multipolar state of NpO2, which is acharacteristic magnetic states without inducing magnetic dipole moments,[1] and find that, while the mostcommon non-dipolar degrees of freedom (e.g., electric quadrupoles and magnetic octupoles) are active in the orderedphase, both the usually neglected higher-order multipoles (electric hexadecapoles and magnetic triakontadipoles)
have at least an equally significant effect in the ground states of NpO2. The method is further applied to thestudy of hidden order (HO) problem of URu2Si2,[2, 3] in which the genuin order parameter in the lowtemperature phase has been a mystery for many years. The first-principles approach combined with thegroup theoretical analysis brought rich harvest for understanding the electric/magnetic character of the
MPO states as promising ordered states of the HO phase. We found the antiferroic magnetic MPO states
are especially advantageous for concealing the order parameter, and the itinerant character of f electronsof URu2Si2 induce only tiny magnetic moments even though the symmetry allows the presence.[3]1.

M.-T. Suzuki, N. Magnani, and P. M. Oppeneer, Phys. Rev. B 88, 195146 (2013); ibid. 82,
241103(R) (2010).

2.

H. Ikeda, M.-T. Suzuki, R. Arita, T. Takimoto, T. Shibauchi, Y. Matsuda, Nat. Phys. 8, 528 (2012).

3.

M.-T. Suzuki and H. Ikeda, arXiv:1409.5602 (2014).

P-74

Crystal orientation dependence of the carrier type in IrO2:
A first-principles study
W. Sano1,2, T. Koretsune2, and R. Arita2
1
Department of Applied Physics, The University of Tokyo, Japan
E-mail: sano@moegi.t.u-tokyo.ac.jp
2
CEMS, RIKEN, Japan
In simple metals and semiconductors, the type of carriers determines the transport properties of thesystem. Thus, if it changes depending on the crystal orientation, we have an intriguing chance to control
the electric transport just by rotating the sample. While the band dispersion usually takes its
maximum/minimum at Γ point in the Brillouin zone (BZ), such anisotropic states often emerge aroundthe BZ boundary. To design materials having anisotropic low-energy states near the edge of the BZ, one
can consider exploiting band degeneracies in the electronic structure. In fact, it has been well known that
if the system has screw and glide symmetries and does not experience any phase transitions due toelectron correlations, a characteristic band degeneracy appears and can form Fermi pockets at the BZ
boundary [1,2]. Such materials can indeed provide a unique playground to explore the possibility tocontrol the type of carriers.
Prototypical systems having screw and glide symmetries are compounds with rutile structure. Amongthem, IrO2 is promising in that it has no long range order (which usually opens a gap at the BZ
boundary) and stays metallic even at low temperatures. Recently, it has been observed that the Hall
coefficient of IrO2 thin films changes its sign depending on the orientation of the crystal growth [3].
Motivated by this experiment, we calculate the Hall coefficient based on density functional theory and
Boltzmann transport theory, and obtain results, which quantitatively agree well with the experiment. In
the presentation, we also discuss the relation between the anisotropy of carriers and the sticking-together
band using a simplified toy model.
1.

V. Heine, Group Theory in Quantum Mechanics (Pergamon Press, New York, 1960)

2.

S. A. Parameswaran, A. M. Turner, D. P. Arovas, and A. Vishwanath, Nature Physics 9, 299 (2013).

3.

M. Uchida et al, in prep.

P-75

First-principles calculation of Hubbard U parameter forgap states in dilute magnetic semiconductors
T. Fukushima*, H. Katayama-Yoshida*, K. Sato**, G. Bihlmayer***, P.
Mavropoulos***, D. S. G. Bauer***, R. Zeller*** and P. H. Dederichs**** Graduate School of Engineering Science, Osaka University, Japan
E-mail: fuku@mp.es.osaka-u.ac.jp** Graduate School of Engineering, Osaka University, Japan*** Peter Gruenberg Institut and Institute for Advanced Simulation,
Forschungszentrum Juelich and JARA, Germany
Since the discovery of carrier induced ferromagnetism in dilute magnetic semiconductors (DMS), i. e.,semiconductors doped with magnetic impurities, many experimental and theoretical efforts have been
devoted to the creation, characterization and understanding of these materials, with the aim of realizing asemiconductor spintronics. On the theoretical side, the electronic structures and magnetic properties ofmany DMS materials such as (Ga,Mn)N, (Ga,Mn)As or (Zn,Cr)Te have been investigated using the
local density approximation (LDA) of density functional theory. However, since the magnetic impurities
used in DMS are usually 3d transition atoms, correlation effects are important in these materials, which
can be described only poorly by LDA. An important parameter describing correlation effects is the U
parameter of the Hubbard model, which is an essential input in LDA+U calculations and dynamicalmean field theory.
In this work, on the basis of constrained density functional theory, we present ab initio calculations for
the Hubbard U parameter of transition metal impurities in DMS, choosing Mn in GaN as an example.
The calculations are performed by two methods: (i) the Korringa–Kohn–Rostoker (KKR) Greenfunction method for a single Mn impurity in GaN and (ii) the full-potential linearized augmented planewave (FLAPW) method for a large supercell of GaN with a single Mn impurity in each cell. Bychanging the occupancy of the majority t2 gap state of Mn, we determine the U parameter either fromthe total energy differences E(N+1) and E(N−1) of the (N±1)-electron excited states with respect to theground state energy E(N), or by using the single-particle energies for n0±1 occupancies around thecharge-neutral occupancy n0 (Janak’s transition state model). The two methods give nearly identicalresults. Moreover the values calculated by the supercell method agree quite well with the Green function
values. We point out an important difference between the ``global'' U parameter calculated using Janak’s
theorem and the ``local'' U of the Hubbard model.
1. T. Fukushima, H. Katayama-Yoshida, K. Sato, G. Bihlmayer, P. Mavropoulos, D. S. G. Bauer, R.
Zeller and P. H. Dederichs, J. Phys.: Condens. Matter, 26 274202 (2014)

P-76

Ab initio derivation of low-energy effective model basedon constrained many-body perturbation theory
Kazuma Nakamura1, Shiro Sakai2, Yoshiro Nohara3, Yoshihide Yoshimoto4
E-mail: kazuma@mns.kyutech.ac.jp
1

Quantum Physics Section, Kyushu Institute of Technology, Japan
2

3

Center for Emergent Matter Science, RIKEN, Japan

Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
4

Department of Information Science, University of Tokyo, Japan

Aiming at ab initio understanding of real materials with strong electronic correlations, we develop a
downfolding scheme based on constrained many-body perturbation theory [1,2]. The main idea of thedownfolding scheme is to utilize the energy hierarchy of the system [2]: While the electronic degrees of
freedom near the Fermi level require an accurate treatment, the high-energy degrees of freedom can betreated approximately. We construct an effective model with only low-energy degrees of freedom, whichis to be solved with some many-body technique, by taking into account the effect of high-energy electrons
through a renormalization of the model parameters. We employ the constrained GW scheme for the
one-body part of the low-energy model and the constrained RPA for the two-body part, where constraints
for the self energy and polarization relevant to the low-energy propagator are introduced [1,2]. The
renormalized transfer integrals and screened Coulomb/exchange interactions are defined on the basis of
the maximally localized Wannier orbitals [3]. Thus, the low-energy frequency-dependent effective model
is derived from the whole high- plus low-energy system with an ab initio calculation.
In this work, we apply the constrained GW and RPA methods to the derivation of the extended
Hubbard-type model of alkali-cluster-loaded-in-zeolite system [4]. To check the quantitative accuracy ofthe calculated model parameters, we derive the Heisenberg model as a low-energy model of the extended
Hubbard model via the second-order perturbation. We find that the estimated antiferromagnetic couplings
are consistent with the experimental temperature dependence of the spin susceptibility. An effect of thestarting wavefunction, i.e., that based on either the local-density or Hartree-Fock approximation, on thederived parameters will also be discussed.
[1] F. Aryasetiawan, et al, Phys. Rev. B 70, 195104 (2004); I. V. Solovyev and M. Imada, Phys. Rev. B 71,
045103 (2005).
[2] M. Imada and T. Miyake, J. Phys. Soc. Jpn. 79, 112001 (2010).
[3] I. Souza, N. Marzari, and D. Vanderbilt, Phys. Rev. 65, 035109 (2001).
[4] K. Nakamura, T. Koretsune, R. Arita, Phys. Rev. B 80, 174420 (2009).

P-77

Material designs of plasmonic nanomaterials on oxides
Hiroaki Matsui* and Hitsohi Tabata** Graduate School of Engineering, The University of Tokyo, Japan
E-mail: hiroaki@ee.t.u-tokyo.ac.jp“Plasmonics” have recived much attention because surface plasmons (SPs) excited on metalnanostructures produce high electric fields, which have widely contributed for enahnced optoelectonic
properties. Thus far, studies concerning plasmonic nanomaterials have progressed with an focus on
metal materials (e.g. Ag and Au). Recenlty, non-metal materials, such as oxides, nitrides and carbons,
have been gathered attention for infrared (IR) optics. It is expected that tranparent oxide semicodncutors(TOSs) are candidates for low-loss plasmonic materials in the near-IR. Above all, TOSs with conduction
bands of s-orbitals ususlly show small effective masses (me*), high mobilities ( e) and high electron
density (ne), which provides low ohmic losses (small imaginary part) and absence of interband
transitions like those exhibited by Ag and Au metals. The electronic band strcutures of TOSs exhibits
the low condcution loss in the near-IR, leading to high performance of SPs.
In this presentation, we initially report theoretcial viewpoints of SPs on TOSs, clearing difference inplasmonic mechanism between metals and TOSs. It will be experimentally evidenced plasmonic
response in TOSs. In particular, plasmonic resonance can be tuned by electron density in a manner thatis not as readily available in metals, which provides infomration for the physcial interpretation inplasmonic resonances of TOSs. Finally, we introduce a case study for near-IR applications fromtheoretical and experimental appraches. Three-dimensinally stacked nanoparticle sheets give selective
high reflectance in the near-IR, contributing for thermal sheidings of solar energy in order to realize
energy and power-saved society. This work deomnstrate the useful potential as altarnative plasmonic
materials based on TOSs.
1. W. Badalawa, H. Matsui, et al. Appl. Phys. Lett. 99, 011913 (2011).
2. H. Matsui, W. Badalawa, et al. Advanced Optical Materials 1, 397 (2013).
3. H. Matsui, S. Furuta et al. Appl. Phys. Lett. 104, 211903 (2014).
4. H. Matsui, W. Badalawa, et al. Appl. Phys. Lett. 105, 041903 (2014).

P-78

Quantum interference between the dynamics of molecular
exciton and interface plasmons in scanning tunnelingmicroscope-induced light emission
K. Miwa*, H. Imada*, M. Sakaue**, H. Kasai** and Y. Kim*
* Surface and Interface Science Laboratory, RIKEN, Japan
E-mail: kuniyuki.miwa@riken.jp** Graduate School of Engineering, Osaka University, Japan
Recently, many attempts have been made to enhance luminescence intensities of molecules and toobserve new fascinating phenomena by utilizing interface plasmons of metal nanostructures. In lightemission induced by the tunneling current of scanning tunneling microscope (STM) from molecules on
metal substrates, interface plasmons localized near the tip-substrate gap region play important roles inelectronic/vibrational excitations and radiative decays of the molecule [1]. Recent experimental results
have also suggested that the dynamics of molecules (e.g., energy emission and absorption) can affect the
optical properties mediated by interface plasmons [2]. Since the dynamics of molecules and interface
plasmons have influence on each other, quantum many-body effects originating from interplay between
these dynamics are expected to occur. To unveil these effects from a microscopic point of view, it isneeded to investigate the dynamics of the molecule and interface plasmons within the framework ofquantum many-body theory. In this study, we construct an effective model of the system and investigate
the effects of coupling between a molecular exciton and an interface plasmon (exciton-plasmon
coupling) on the luminescence properties using the nonequilibrium Green’s function method [3-6].
The results show that the enhancement by the molecular modes and the energy absorption by themolecule lead to peak and dip structures in the luminescence spectra of interface plasmons. Moreover, it
is found that the re-absorption of energy by interface plasmons leads to suppression of luminescenceintensity in the energy range near the plasmon mode. The additional peak structure near the energy ofmolecular excitonic mode arises owing to interference between energy absorption processes of themolecule and interface plasmons. The developed theory can explain mechanisms for occurrence ofprominent peak and dip structure observed in recent experiments. The details of variation in theseluminescence spectral profiles will be discussed in our presentation.
1. Z. C. Dong et al., Nat. Photonics 4, 50 (2010).
2. N. L. Schneider and R. Berndt, Phys. Rev. B 86, 035445 (2012).
3. K. Miwa, M. Sakaue, and H. Kasai, J. Phys. Soc. Jpn. 82, 063715 (2013).
4. K. Miwa, M. Sakaue, and H. Kasai, J. Phys. Soc. Jpn. 82, 124707 (2013).
5. K. Miwa, M. Sakaue, and H. Kasai, Nano. Res. Lett. 8, 204 (2013).
6. K. Miwa, M. Sakaue, B. Gumhalter and H. Kasai, J. Phys.: Condens. Matter 26, 222001 (2014).

P-79

Interaction between L-alanine and plasma generated inhydrogen peroxide water

M. Shinohara, Y. Yoshida, N. Maruno, Y. Taniguchi, Y. Yoshida, K. Ito, Y. Nakano,Y. Matsuda, H, Fujiyama
Graduate School of Engineering, Nagasaki University, Japan
E-mail: sinohara@nagasaki.ac.jp
Plasma bioapplication is a promising application. To realize the plasma bioapplication, the interaction ofplasma with biomolecules should be clarified. In genral, biomolecules have complicated structures. The

the simple structures are required to understand basic phenomena. Then, we chose L-alanine, because it

is a amino acid, which is a component of protein. The chemical structure is well-known, then we caneasily identify the changes in chemical states of L-alanine exposed to plasma. In this study, we alsochose the plasma generated in solution, because the bio-molecules in living system is usually covered
with water. We investigated the interaction between L-alanine and plasma generated in hydrogen

peroxide water. Here, we used hydrogen peroxide water, because it is difficult to generate plasma inpure water, but it is easy to generate it in hydrogen peroxide water. We in-situ and real-time measured

the chemical states of L-alanine exposed to the plasma, with infrared absorption spectroscopy inmultiple internal reflection geometry (MIR-IRAS). The IR absorption spectra indicate that the amount of

C=O bonds decreased with the plasma exposure. The chemical structure of L-alanine is destroyed from

C=O bonds in the molecule. We also observed the shape of residues after evaporation of the L-alanine-dissolved hydrogen peroxide water with microscope. Approximately-linear shapes were observed i in
the residues acquired from the water without plasma generation, while many branched linear shapes

were obsereved in the residues from the water with plasma generation. The linear shape would be due topolar molecules bonding to each other, while many branched shapes would be due to destruction ofpolar molecular strucures. We also discuss the chemical changes in glycine exposed to plasma generated
in hydrogen peroxide water in the presentation.

P-80

Topological surface state in
topological crystalline insulator SnTe thin films*

R. Akiyama, *K. Fujisawa, *T. Yamaguch, **M. Nakatake, ***A. Kimura, *S. Kuroda* Institute of Materials Science, University of Tsukuba, Japan
E-mail: akiyama@ims.tsukuba.ac.jp** Hiroshima Synchrotron Radiation Center, Hiroshima University, Japan*** Graduate School of Science, Hiroshima University, Japan

SnTe is known as a new type of topological insulator(TI), namely, topological crystalline insulator(TCI),
in which the metallic surface state(SS) is protected by the mirror symmetry of the crystal, instead of thetime-reversal symmetry in TI. There have so far been several reports on the electronic properties of TCI
such as the Shubnikov-de Haas(SdH) oscillation in SnTe thin films grown on Bi2Te3[2], the AB effectand AAS oscillations in a SnTe nanowire[3], and weak antilocalization(WAL)[4][5]. However, thedetailed quantum transport by the SS of a SnTe thin film has not yet been understood well. In thetransport measurement of SnTe, it is regarded as difficult to distinguish a component of the surface
transport from a large contribution of the bulk transport because Sn vacancies are easily formed in ahigh density, which results in a high concentration of bulk holes. In this study, we have successfully
observed a characteristic feature of the 2D transport in the high-quality SnTe thin films. We have grown
SnTe thin films on a BaF2 (111) substrate by MBE. By optimizing the growth conditions, we could
obtain (111)-oriented single-crystal films without inclusions grown in any other orientations or those ofdifferent phases. In the longitudinal magnetoresistance at 4 K we have observed the weak localization
effect of 2D electrons. Furthermore, we measured angle-resolved photoemission spectroscopy toobserve the band structure of the surface state. We
will discuss the surface state based on the analysis of
those results.
1. Y. Tanaka et al., Nat. Phys. 8, 800 (2012).
2. A. A. Taskin et al., Phys. Rev. B 89, 121302(R)(2014).
3. M. Safdar et al., Nano Lett. 13, 5344 (2013).
4. B. A. Assaf et al., Appl. Phys. Lett. 105, 102108(2014).
5. R. Akiyama et al., Jour. of Phys. Conf. Ser. in print[ArXiv 1408.4226]

Fig1: The angular dependence of themagneto-conductance at 4K. The components
which are different depending on the field
angle are attributed to 2D WAL.

P-81

End-cap geometry dependence of power conversion
efficiency of solar cells based on capped-carbon nanotubes
Shota Ono*, Kousei Tanikawa**, Riichi Kuwahara***, and Kaoru Ohno** Dept. of Physics, Graduate School of Engineering, Yokohama National Univ., Japan
E-mail: shota-o@ynu.ac.jp** School of Engineering Science, Yokohama National Univ., Japan*** Accelrys K. K., Kasumigaseki Tokyu Building 17F, Japan
We theoretically propose a new type of organic photovoltaic cells based on “capped”-carbon nanotubes(CNTs). The power conversion efficiency of the solar cell is estimated to be 25% [1], which approaches
the upper limit of single-junction inorganic photovoltaic cells of the Schockley-Queisser limit [2].
The full solar cell design can be found in Ref. [1]. We consider here a heterojunction between acapped-CNT and zinc-phthalocyanine (ZnPc), as shown in the inset of Fig. 1. The principle of power
generation is decomposed into three elements: (i) when a photon is absorbed by ZnPc, an electron is
excited into ZnPc-LUMO, leaving a hole behind, (ii) the excited electron moves to a lower empty state
localized near the cap of CNT, and (iii) the electron moves freely along the CNT axis and recombinewith the hole at ZnPc, which generate an electric current. The efficiency of our solar cells is computed
for CNTs with different end-cap geometry, using a formula given in Ref. [3]. The eigenenergies in ourcomplex system are obtained within the density functional theory implemented in the DMol 3 code [4].
Figure 1 shows the efficiency for sorlar cells based on capped-(n,n)CNT and ZnPc: as n decreases,
the efficiency increases. This may be attributed toa quantum size effect on the orbital localized at
the cap. This result opens the way toward adevelopment of solar cells with high efficiency.
Fig. 1: n-dependence of the power conversion
efficiency. As a reference, the efficiency of the solar
cell based on C60/ZnPc is shown (13.8%). Inset: aheterojunction between capped-(n,n)CNT and ZnPc.

1. S. Ono, R. Kuwahara, and K. Ohno, J. Appl. Phys. 116, 054305 (2014).
2. W. Shockley and H. J. Queisser, J. Appl. Phys. 32, 510 (1961).
3. K. Seki, A. Furube, and Y. Yoshida, Appl. Phys. Lett. 103, 253904 (2013).
4. B. Delley, J. Chem. Phys. 92, 508 (1990); J. Chem. Phys. 133, 7756 (2000).

P-82

Computational design of chalcogenide- and pnictogenidebased photovoltaic solar cell materials
K. Sato*1, 2, D. Deguchi1, T. Kotani3, T. Kakeshita1 and H. Katayama-Yoshida4
1
Graduate School of Engineering, Osaka University, Japan
2
PRESTO, Japan Science and Technology Agency (JST), Japan3
Department of Applied Mathematics and Physics, Tottori University, Japan
4
Graduate School of Engineering Science, Osaka Universityj, Japan*E-mail: ksato@mat.eng.osaka-u.ac.jp
The fabrication of sustainable and high-efficiency photovoltaic solar cell (PVSC) materials is one of themost important social issues to be solved for next generation. In this presentation, we present ab initio
calculations concerning to the design of such PVSC materials based on chalcogenides and pnictogenides.
Firstly, for sustainable PVSC we explore about 15 calcogenides and pnictogenides in addition to thechalcopyrite-type compounds. For these compounds, we estimate conversion efficiency based on the
Shockley-Queisser (SQ) theory [1] with the ab initio optical absorption coefficient calculated by thehybrid functional (HSE06) [2] implemented in the VASP [3]. For more accurate calculation of opticalproperties, for typical cases we also employ Quasi-Particle GW method [4]. The effect of non-radiative
recombination to the efficiency is included by the model proposed by Yu et al. [5]. The efficiency of
FeS2, Zn3P2, Sb2S3, CuSbS2, ZnSnP2, ZnSnN2 are calculated to be higher than 20%. It is also found that
FeS2, Sb2S3 and CuSbS2 are suitable for thin-film PVSC due to their large photo-absorptivity.
Next, we propose that the self-organization enhances the efficiency of Cd(Te, S). We perform cluster
expansion of total energy of the system and simulated self-organization of nano-structures in Cd(Te, S)
by using Monte Carlo method. It is found that layered structure becomes stable by applying strain during
the crystal growth. The optical absorption coefficient and the SQ limit are calculated for the selforganized layered structure. It is shown that the efficiency limit does not change so much due to thenano-structure formation. However, our calculation shows spatial separation between photo-generated
electrons and holes. This might enhance the efficiency due to the suppression of recombination [6].
1. W. Shockley, H. J. Queisser, J. Appl. Phys. 32, 510 (1961).
2. J. Heyd et al., J. Chem.Phys.118, 8207 (2003), 124, 219906 (2006).
3. G. Kresse and J. Furthmueller, Phys. Rev. B 54, 11169 (1996).
4. T. Kotani, M. van Schilfgaarde and S. V. Faleev, Phys. Rev. B 76, 165106 (2007).
5. L. Yu and A. Zunger, Phys. Rev. Lett. 108, 068701 (2012).
6. M. Oshitani et al., Appl. Phys. Express 4, 022302 (2011).

P-83

Survey of high Tc materials in hard semiconducting
boron crystals
K. Shirai, K. Sakuma, and N. Uemura
The Institute of Scicentific and Industrial Reseasrch, Osaka University, Japan
E-mail: koun@sanken.osaka-u.ac.jp
Since this century opened, many important discoveries on superconductivity of born and relatedmaterials have taken place; superconductivity of β-boron at high pressure, B-doped diamond, and MgB2.
Boron is light element and its compounds are commonly hard materials, impying strong electron-phonon
interaction. These features may be favourable for high-Tc superconductivity. Although icosahedral boron
crystals are semiconductor, high Tc could be obtained if sufficient amounts of doping are made. The
present project is aimed at achieving metallization of boron and related compounds. The following threebasic strategies have been employed for this purpose.
(1) High pressure technique
Elemental boron crysatls are the last cyrstals whose phase diagram were not known. After discoveryof the superconductivity of β-boron at 160 GPa, we have, for the first time, predicted the phase diagramof boron [pps b244 303]. This phase diagram shows that α-boron is the most stable phase in highpressure, and accordingly α-boron is a suitable one for examining superconductivity. On this line of thisthought, experimentalists discovered the superconductivity of α-boron at high pressure. We havedisclosed the mechanism for the metallization of α-boron [JSPS 78 08714; 80 084601].
(2) Heavy doping
For practical applications, metallization at normal pressure is indispensible. Doing method is themost suitable one. Li-doping on α-boron was proposed by others. Contrary to this prediction, it was
experimetally difficult to dope Li to α-boron. Our study explains why it is difficult, and estimated theupper limit of dopoing amount [PRB84 094117]. Later, experimentalists succeeded to dope Li to αboron, leading to superconductivity. The amount of Li was approximately in agreement with our
prediction. This upper limit could be raised by using high-pressure doping, which is our proposal.
(3) Use of compounds (borron carbide)
A boron carbide of specific composition, B13C2, is expected to have a high Tc of about 40 K.
However, experimentally, even metallic behaviour are not observed. We have clarified the reason of thisdiscrepancy [PRB90 064109]. The essential problem of this material is that the electron defficiency andthe strong covalent character yield intrincid defect states associated with off-stoichiometry, withsatisfying the valence requirement. In the last year of this project, study for overcoming this difficulty isin progress.

P-84

Density Functional Theory for Plasmon-Assisted
Superconductivity
R. Akashi* and R. Arita*** Department of Physics, The University of Tokyo, Japan
E-mail: akashi@cms.phys.s.u-tokyo.ac.jp** RIKEN Center for Emergent Matter Science (CEMS), JapanOne of the most fascinating goals in the studies of superconductivity is the predictive calculation ofsuperconducting transition temperatures (Tc) based on a unified theoretical framework. Since theelectron-lattice and electron-electron interactions which cause superconducting transition strongly
depend on the electronic and lattice structures, a proper description of the superconducting mechanisms
with an accurate treatment of the structures is crucial. For a conventional phonon-induced
superconducting mechanism, such a unified framework is established by the recent progress in thedensity functional theory for superconductors [1] (SCDFT); the current SCDFT-based calculation
scheme systematically reproduces Tc observed by experiments in the conventional systems such as
niobium and MgB2, with discrepancies no more than a few kelvin. However, further extensions
including other mechanisms are essential to treat more general materials.
Recently, we extended the SCDFT-based scheme to include a plasmon mechanism of superconductivity[2]. In dilute uniform electron gas, it has been proposed that plasmon-induced screened dynamical
Coulomb interaction induces superconducivity [3]. This mechanism is also expected to become relevant
in a wider range of systems because it can cooperate with the conventional phonon mechanism. Our
extended scheme enables us to evaluate the effects on Tc of the plasmon and phonon mechanisms onequal footing. In the presentation, we introduce the formulation and the recent application to several swave superconductors.
1. M. Luders, et al., Phys. Rev. B 72, 024545 (2005); M. A. L. Marques et al., ibid, 024546 (2005).
2. R. Akashi and R. Arita, Phys. Rev. Lett. 111, 057006 (2013); J. Phys. Soc. Jpn. 83, 061016 (2014).
3. Y. Takada, J. Phys. Soc. Jpn. 45, 786 (1978).

P-85

Superconductivity in Pseudoferroelectric Crystals:
Case of n-doped SrTiO3Masahiro Sakurai and Yasutami Takada
The Institute for Solid State Physics, The University of Tokyo, Japan
E-mail: sakurai@issp.u-tokyo.ac.jp
Superconductivity near the ferroelectric quantum critical point is an intriguing issue of research andfrom this perspective, strontium titanate (STO: SrTiO3) and its derivatives such as CaxSr1-xTiO3 attract
attention in recent years. STO, a widely used perovskite oxide with a band gap of 3.2 eV, is close to adisplacive-type ferroelectric transition. When doped with substituting Nb for Ti or removing oxygen, thesample shows metallic behavior. Below 0.5 K, it exhibits superconductivity where the carrier density
dependence of the critical temperature Tc(n) has a dome shape, as is the case in high-Tc cuprates. In 2013,
Lin et al. found that, in oxygen-deficient samples, superconductivity survives even at n = 5.5×1017 cm-3[1]. They also discovered another Tc dome in the doping range lower than previously achieved in Nbdoped sample [2]. In this work, we elucidate superconductivity in n-doped STO in the ferroelectric
displacive soft phonon mechanism by the calculation of Tc in the framework of using the single-band
pairing interaction in the Kirzhnits-Maksimov-Kohmskii scheme [3] and determining the Coulomb
pseudopotential from first principles [4]. Based on the microscopic Hamiltonian H of the system, we
include the soft-phonon exchange effect in the pairing interaction in the long-range dielectric formalism,
which is valid in low-density systems. In considering H, the one-electron dispersion is assumed to beparabolic with an effective mass m*. For the computation of the pairing-interaction kernel in the BCStype gap equation which involves multi-dimensional summation, the code is parallelized with MPI. The
power method is used to obtain Tc by solving the gap equation. With the values of parameters in H takenfrom experiments, the Tc dome observed in Nb-doped samples (i.e., in higher doping range) isreproduced well. The calculated Tc near the optimal doping is found to be a few percent larger than thatof previous calculation [4] where an approximate formula was adopted to solve the gap equation. We
also find that a trend in Tc for oxygen-deficient samples (i.e., lower dopings) is captured by using asmaller m*, which agrees with mesurements, and a smaller phonon frequency, indicating the approach toa ferroelectric transition.
1. X. Lin et al., Phys. Rev. X 3, 021002 (2013).
2. X. Lin et al., Phys. Rev. Lett. 112, 207002 (2014).
3. D. A. Kirzhnits, E. G. Maksimov, and D. I. Kohmskii, J. Low Temp. Phys. 10, 79 (1973).
4. Y. Takada, J. Phys. Soc. Jpn. 49, 1267 (1980).

P-86

Possible superconductivity in naphthalene-based organic
molecular crystal
T. Koretsune1, R. Akashi2, S. Sato3,4, H. Isobe3,4 and R. Arita1,4
1
RIKEN CEMS, Japan
E-mail: takashi.koretsune@riken.jp
2
Graduate School of Science, University of Tokyo, Japan
3
Graduate School of Science, Tohoku University, Japan
4
JST ERATO Isobe Degenerate π-Integration Project, AIMR, Japan
In organic molecular crystals, the energy scale of phonon frequencies is relatively high and the densityof states can also be large due to the narrow band width. Thus, it should be promising to design
superconducting materials using organic molecular crystals. However, as far as we know, only fullerenecompounds are known to have high transition temperatures. This is probably because it is difficult todope carriers in organic crystals with keeping the cristallinity.
Here, we consider [6]cyclo-2,7-naphthylenes([6]CNAP), where six naphthalenes form a cyclic arraythrough single-bond linkages[1]. In this material, due to its cyclic structure, it is expected that alkali
atoms can be doped inside the naphthalene rings without disturbing crystallinity. In fact, we confirmedthat there are Raman peaks specific to this cyclic structure by comparing theoretical calculations andexperiment. For this material, we compute the electronic structure, phonon dispersion, and electronphonon couplings, and estimate the superconducting transition temperature from first-principles
calculations. By assuming that alkali-atom doping only shifts the chemical potential, it is found that theestimated transition temperature is as high as that of fullerene compounds. We will also discuss thepossibility of superconductivity in [n]cyclo-meta-phenylenes[2].
1.

W. Nakanishi et al., Angew. Chem. Int. Ed. 50 (2011), 5323.

2.

J. Y. Xue et al., J. Org. Chem. (2014) in press.

P-87

DMFT+FLEX approach tounconventional superconductivity
Motoharu Kitatani, Naoto Tsuji, and Hideo Aoki
Department of Physics, University of Tokyo, Hongo, Japan
E-mail: kitatani@cms.phys.s.u-tokyo.ac.jp
Computational methods for strongly correlated systems are still challenging, especially forsuperconductors.

Primary reason for this is one has to simultaneously deal with Mott physics and theanisotropic d-wave pairing.

Here we propose a new algorithm to combine the dynamical mean field

theory (DMFT) for the former and the fluctuation exchange approximation (FLEX) for the latter tocapture strongly correlated systems especially to obtain a phase diagram for d-wave superconductivity
and its “Tc dome”[1]. The DMFT+FLEX method (Fig. below), which can also be viewed as a proposal
for a new Luttinger-Ward functional, describes the momentum-dependent pairing interaction for
describing anisotropic pairing along with the local correlation effect that is important in Mott physics.
We have applied the new formalism to the two-dimensional repulsive Hubbard model to obtainsuperconducting transition temperature. The result does indeed exhibit a Tc-dome structure. We havetraced back the origin of the dome to the local vertex correction from DMFT that gives a filling
dependent effect on the FLEX self-energy.

[1] M. Kitatani, N. Tsuji and H. Aoki, in prep.

P-88

A density functional design of an interaction-driven
topological insulator in cold atoms on an optical lattice
S. Kitamura, N. Tsuji and H. Aoki
Department of Physics, The University of Tokyo, Hongo, Tokyo, Japan
E-mail: kitamura@cms.phys.s.u-tokyo.ac.jp
One of the most remarkable consequences of many-body effects on topological systems is a possibilityof interaction-induced spontaneous symmetry breaking towards topological insulators, which is called
the “topological Mott insulator” [1]. While the topological Mott insulating phases are proposed in
hypothetical tight-binding models with long-range interactions [1,2], condensed-matter realization of the
topological Mott insulator has yet to be achieved. On the other hand, realization and detection of usual
topological phases have been extensively examined in cold-atom systems. Motivated by this, we
propose here a design for realizing an interaction-driven topological Mott insulator in cold atoms on
optical lattices [3].
While one key ingredient, inter-site interactions, required for topological Mott insulators is too small in
cold-atom systems with short-range interactions, we overcome the difficulty by employing spindependent optical lattices. The idea is then confirmed by quantitatively demonstrating, with a densityfunctional theory for cold-atom systems [4], here extended to accommodate non-collinear spin density
functionals, that the proposed system does indeed exhibit a phase transition from a semimetal to a Chern
insulator as the repulsive interaction is increased (Figs.1,2).

Fig.1: Topological gap in the proposed system

Fig.2: Berry’s curvature in the topological Mott

against the s-wave scattering length as.

insulating phase.

1. S. Raghu, X.-L. Qi, C. Honerkamp, and S.-C. Zhang, Phys. Rev. Lett. 100, 156401 (2008).
2. K. Sun, H. Yao, E. Fradkin, and S. Kivelson, Phys. Rev. Lett. 103, 046811 (2009).
3. S. Kitamura, N. Tsuji, and H. Aoki, in prep.
4. P. N. Ma, S. Pilati, M. Troyer, and X. Dai, Nat. Phys. 8, 601 (2012).