Search query: Electronic structures and theoretical modelling of two-dimensional

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abstract: Atomically thin group VIB transition metal dichalcogenides (TMDs) have recently emerged as a new class of two dimensional (2D) semiconductors with extraordinary properties including the direct band gap in the visible frequency range, the pronounced spin orbit coupling, the ultra strong Coulomb interaction, and the rich physics associated with the valley degree of freedom. These 2D TMDs exhibit great potential for device applications and have attracted vast interest for the exploration of new physics. 2D TMDs have complex electronic structures which underlie their physical properties. Here we review the bulk electronic structures of these new 2D materials as well as the theoretical models developed at different levels, along which we sort out the understanding of the origins of a variety of properties observed or predicted.
author_names: Gui-Bin Liu

Di Xiao

Yugui Yao

Xiaodong Xu

Wang Yao
title: Electronic structures and theoretical modelling of two dimensional group VIB transition metal dichalcogenides.
venue: Chemical Society reviews
year: 2015

author_names: Gui-Bin Liu

Di Xiao

Yugui Yao

Xiaodong Xu

Wang Yao
title: Electronic Structures and Theoretical Modelling of Two Dimensional Group VIB Transition Metal Dichalcogenides
year: 2015

abstract: The electronic properties of phosphorus delta doped structures in silicon, and germanium, are studied using a variety of theoretical approaches. The importance of such phosphorus systems cannot be understated. They can be structurally confined in one, two
author_names: J A C Smith
title: Modelling the electronic properties of zero one and two dimensional phosphorus systems in semiconductors
year: 2016

abstract: Abstract Charged impurities influence functional properties of two dimensional materials and a detailed theoretical understanding of charged defects is required to enable a rational design of defect engineered nanomaterials for applications in ultrathin devices. To achieve this goal, we have developed multiscale approaches that combine atomistic first principles theories, such as density functional theory, with coarse grained continuum models, such as effective mass models. This allows us to model large supercells which are required to accurately describe the slow decay of the screened defect potential and the defect induced changes in the electronic properties of the two dimensional host material. I will describe the results of our multiscale calculations for charged defects in doped graphene and in transition metal dichalcogenide monolayers which have revealed novel mechanisms for controlling and tuning the electronic structure of two dimensional materials.
author_names: Johannes Lischner
title: Multiscale modelling of charged impurities in two dimensional materials
venue: Computational Materials Science
year: 2019

abstract: Thiophene/benzene fused p conjugated systems are normally employed as the core units of two and three dimensionally expanded small molecule hole transporting materials (HTMs) to improve their electronic and charge transport properties, whereas comparison studies between two dimensional and three dimensional core conformations are less reported. To further find useful clues for the design of highly efficient small molecule HTMs and to find new core units, in this work, four HTM molecules are designed by employing triphenylene, benzotrithiophene, triptycene, and thiophenetriptycene as the core units, and simulated with density functional theory combined with the Marcus hopping model. Our results show that all the considered HTMs display appropriate molecular energy levels, less optical absorption in the visible light region and large Stokes shifts, and high hole mobilities (9.80 x 10 2 cm2 V 1 s 1) Compared with the two dimensional core structures, the three dimensional cores exhibit evident superiorities with the same chemical components. Meanwhile, we also find that the quasi degenerate HOMO energy levels will be helpful to enlarge the transfer integrals between adjacent molecules, and further to promote the hole transport in HTMs. By considering the various elements simultaneously, these investigated HTMs (S 1 S 4) with thiophene and benzene fused cores can be expected as potential promising candidates to help create more efficient solar cells.
author_names: Zhu-Zhu Sun

Shuai Feng

Chuantao Gu

Nian Cheng

Jiangfeng Liu
title: Probing effects of molecular conformation on the electronic and charge transport properties in two and three dimensional small molecule hole transporting materials: a theoretical investigation.
venue: Physical chemistry chemical physics PCCP
year: 2019

abstract: Combining the bond order length strength (BOLS) and atomic bonding and electronic model (BB model) with density functional theory (DFT) calculations, we studied the atomic bonding and electronic binding energy behavior of Bi atoms adsorbed on the Li(110) surface. We found that the Bi atoms adsorbed on the Li(110) surface form two dimensional (2D) geometric structures, including letter hexagon galaxy crown field and cobweb shaped structures. Thus, we obtained the following quantitative information: (i) the field shaped structure can be considered the bulk structure; (ii) the field shaped structure of Bi atom formation has a 5d energy level of 22.727 eV, and in the letter shape structure, this energy is shifted to values greater than 0.342 eV; and (iii) the Bi/Li(110) heterojunction transfers charge from the inner Li atomic layer to the outermost Bi atomic layer. In addition, we analyzed the bonding and electronic dynamics involved in the formation of the Bi/Li(110) heterojunctions using residual density of states. This work provides a theoretical reference for the fine tuning of binding energies and chemical bonding at the interfaces of 2D metallic materials.
author_names: Maolin Bo

Liangjin Ge

Jibiao Li

Lei Li

Chuang Yao

Zhongkai Huang
title: Atomic Bonding and Electronic Binding Energy of Two Dimensional Bi/Li(110) Heterojunctions via BOLS BB Model
venue: ACS omega
year: 2021

abstract: This review provides a perspective on recent developments and their implications for our understanding of novel quantum phenomena in the physics of two dimensional organic solids. We concentrate on the phase transitions and collective response in the charge sector, the importance of coupling of electronic and lattice degrees of freedom and stress an intriguing role of disorder. After a brief introduction to low dimensional organic solids and their crystallographic structures, we focus on the dimensionality and interactions and emergent quantum phenomena. Important topics of current research in organic matter with sizeable electronic correlations are Mott metal insulator phase transitions, charge order and ferroelectricity. Highly frustrated two dimensional systems are established model compounds for studying the quantum spin liquid state and the competition with magnetic long range order. There are also unique examples of quantum disordered state of magnetic and electric dipoles. Representative experimental results are complemented by current theoretical approaches.
author_names: Martin Dressel

Silvia Tomi'c
title: Molecular quantum materials: electronic phases and charge dynamics in two dimensional organic solids
year: 2020

abstract: Two dimensional (2D) palladium diselenide (PdSe2 has strong interlayer coupling and a puckered pentagonal structure, leading to remarkable layer dependent electronic structures and highly anisotropic in plane optical and electronic properties. However, the lack of high quality, 2D PdSe2 crystals grown by bottom up approaches limits the study of their exotic properties and practical applications. In this work, chemical vapor deposition growth of highly crystalline few layer =2 layers) PdSe2 crystals on various substrates is reported. The high quality of the PdSe2 crystals is confirmed by low frequency Raman spectroscopy, scanning transmission electron microscopy, and electrical characterization. In addition, strong in plane optical anisotropy is demonstrated via polarized Raman spectroscopy and second harmonic generation maps of the PdSe2 flakes. A theoretical model based on kinetic Wulff construction theory and density functional theory calculations is developed and described the observed evolution of "square like" shaped PdSe2 crystals into rhombus due to the higher nucleation barriers for stable attachment on the (1,1) and (1, 1) edges, which results in their slower growth rates. Few layer PdSe2 field effect transistors reveal tunable ambipolar charge carrier conduction with an electron mobility up to 294 cm2 V 1 s 1 which is comparable to that of exfoliated PdSe2 indicating the promise of this anisotropic 2D material for electronics.
author_names: Yiyi Gu

Hui Cai

Jichen Dong

Yiling Yu

Anna N Hoffman

Chenze Liu

Akinola D Oyedele

Yu-Chuan Lin

Zhuozhi Ge

Alexander A Puretzky

Gerd Duscher

Matthew F Chisholm

Philip D Rack

Christopher M Rouleau

Zheng Gai

Xiangmin Meng

Feng Ding

David B Geohegan

Kai Xiao
title: Two Dimensional Palladium Diselenide with Strong In Plane Optical Anisotropy and High Mobility Grown by Chemical Vapor Deposition.
venue: Advanced materials
year: 2020

abstract: Gold nanomaterials, including one dimensional (1D) gold nanorods (AuNRs) and nanowires (AuNWs) and two dimensional (2D) gold nanoprisms with a large surface area and stability, have attracted widespread research interest. A large number of experimental and theoretical studies have shown that the properties of low dimensional gold nanomaterials depend on their anisotropic shape. In this work, we theoretically conceived a new type of gold nanomaterial, namely, thiolate (SR) monolayer passivated quasi 1D and quasi 2D gold nanocrystals and infinite superstructures, which were formed by the fusion of seed clusters Au28(SR)20, Au36(SR)24, Au44(SR)28 and Au52(SR)32 or the layer by layer growth of gold atoms along the [100] and/or [010] directions. By means of DFT and TD DFT calculations, the structure and properties of these model gold nanocrystals and superstructures are studied in depth. It is found that the passivation of the monolayer of thiolate leads to significantly improved near infrared absorption properties in comparison with the ligand free gold nanocrystals. Upon passivating the thiolate monolayer, the ultrathin 1D gold nanowire and 2D gold nanosheet demonstrate a metal to semiconductor transition. The novel electronic structures, optical absorption and semiconductor to metal transition found in these thiolate protected low dimensional gold nanocrystals suggest that the passivation of the SR ligand is a promising way to tailor the properties of gold nanomaterials.
author_names: Liang Yang

Pu Wang

Zhenhua Yang

Yong Pei
title: Effect of thiolate ligand passivation on the electronic structure and optical absorption properties of ultrathin one and two dimensional gold nanocrystals.
venue: Nanoscale
year: 2020

abstract: Abstract The third order nonlinear optical response of protein molecules to a sequence of infrared (IR) pulses reflects abundant information on the conformational dynamics of these macromolecules. In this chapter, we review the theoretical methods for simulating the protein two dimensional infrared spectroscopy based on molecular dynamic simulations. The chapter starts by constructing the effective fluctuating Frenkel exciton (FE) Hamiltonian based on the classical molecular dynamics simulation and density functional theory electrostatic map. The parameters required are generated from the electronic structure calculations. As a generalization of this Stark model, vibrational solvatochromism is further discussed. Nonlinear response function calculation protocols, such as the sum over states model, cumulant expansion of Gaussian fluctuation, and numerical propagation equations such as the stochastic Liouville equation and numerical integration of the Schrodinger equation are then described in detail. We also demonstrate that the simulation result can be improved by introducing the statistical mechanics techniques such as the integrated tempering sampling method and the Markov state models, which achieve a more comprehensive sampling of the thermodynamics and kinetics.
author_names: Zhijun Pan

Wei Zhuang
title: Theoretical simulation of protein two dimensional infrared spectroscopy
year: 2020