Electronic Properties of Hydrogenated Graphene-Like Materials Under Strains

Honeycomb Lattice ◽

Electronic Band ◽

Hydrogenated Graphene ◽

Zigzag Direction ◽

ABSTRACTThe electronic band structures of the hydrogenated graphene-like materials, graphane, silicane, and germanane, under tensile strains are calculated using first-principles calculation. The imposed tensile strain is in either the armchair or zigzag direction in the honeycomb lattice. It is found that the band gap of graphane gradually increases with the increase of the strain, whereas the band gaps of silicane and germanane decrease with the increase of the strain. There is little effect of the direction of the imposed strain on such strain dependences.

Electronic properties of monolayer molybdenum dichalcogenides under strains

MRS Proceedings ◽

10.1557/opl.2015.466 ◽

2015 ◽

Vol 1726 ◽

Author(s):

J. Sugimoto ◽

K. Shintani

Keyword(s):

First Principles ◽

Tensile Strain ◽

Compressive Strain ◽

Band Gaps ◽

Honeycomb Lattice ◽

Biaxial Strain ◽

Electronic Band ◽

Zigzag Direction ◽

ABSTRACTThe electronic band structures of monolayer molybdenum dichalcogenides, MoS2, MoSe2, and MoTe2 under either uniaxial or biaxial strain are calculated using first-principles calculation with the GW method. The imposed uniaxial strain is in the zigzag direction in the honeycomb lattice whereas the imposed biaxial strain is in the zigzag and armchair directions. It is found that the band gaps of these dichalcogenides almost linearly increase with the decrease of the magnitude of compressive strain, reach their maxima at some compressive strain, and then decrease almost linearly with the increase of tensile strain. It is also found their maximum band gaps are direct bandgaps.

First-principles calculation of influence of nitrogen substituting for oxygen on the crystal structures and electronic band structures of Sr3MgSi2O8-σNσ

Computational Materials Science ◽

10.1016/j.commatsci.2019.03.043 ◽

2019 ◽

Vol 163 ◽

pp. 256-261

Author(s):

Meng Zhang ◽

Ting Song ◽

Xinyang Zhang

Keyword(s):

Crystal Structures ◽

First Principles ◽

Band Structures ◽

Electronic Band ◽

SILICON-BASED HALF-METAL: METAL-ENCAPSULATED SILICON NANOTUBE

NANO ◽

10.1142/s179329200700043x ◽

2007 ◽

Vol 02 (02) ◽

pp. 109-114 ◽

Cited By ~ 7

Author(s):

J. BAI ◽

X. C. ZENG

Keyword(s):

First Principles ◽

Electronic Band ◽

Half Metallic ◽

Half Metal ◽

Silicon Nanostructure ◽

Metal Metal ◽

Silicon Based ◽

Electronic Band Structures ◽

Silicon Nanotube

We performed first-principles calculation to show that a host–guest silicon nanostructure can exhibit half-metallic properties, wherein the host is a single-walled hexagonal silicon nanotube while the guest is a hybrid atomic chain of Mn and Co (encapsulated in the host nanotube). The calculated electronic band structures indicate that the Fermi level intersects only in the spin-up band, whereas the spin-down band exhibits semiconducting characteristics.

Electronic Structure and Ground State Properties of A4[Ag4O4] (A=Na, K and Rb): A First-Principles Study

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.665.43 ◽

2013 ◽

Vol 665 ◽

pp. 43-48

Author(s):

Rajagopalan Umamaheswari ◽

M. Yogeswari ◽

G. Kalpana

Keyword(s):

Electronic Structure ◽

Band Gap ◽

Ground State ◽

First Principles ◽

Density Functional ◽

Electronic Band Structure ◽

Partial Density ◽

Electronic Band ◽

Ground State Properties

The first-principles calculation within density functional theory is used to study in detail the electronic structure and ground state properties of alkali-metal oxoargenates A4[Ag4O4] (A= Na, K and Rb). The total energies calculated within the atomic sphere approximation (ASA) were used to determine the ground state properties such as equilibrium lattice parameter, c/a ratio, bulk modulus and cohesive energy. The theoretically calculated equilibrium lattice constants values are in well agreement with the available experimental values. The electronic band structures, total and partial density of states are calculated. The result of electronic band structure shows that the KAgO and RbAgO are direct band gap semiconductors with their gap lying between the Γ-Γ points, whereas NaAgO is found to be an indirect band gap semiconductor with its gap lying between Z-Γ points.

Novel ultra-hard hexacarbon allotropes from first principles

10.26434/chemrxiv-2022-x4p38 ◽

2022 ◽

Author(s):

Samir F. Matar ◽

Vladimir L. Solozhenko

Keyword(s):

Elastic Constants ◽

Vickers Hardness ◽

Ground State ◽

First Principles ◽

Geometry Optimization ◽

Band Gaps ◽

Electronic Band ◽

Carbon Allotropes ◽

Ground State Structures ◽

Novel ultra-hard hexacarbon C6 allotropes are proposed based on crystal chemistry rationale and geometry optimization onto ground state structures. Similar to diamond, the orthorhombic, tetragonal and trigonal C6 are cohesive networks of C4 tetrahedra illustrated by charge density projections exhibiting sp3-like carbon hybridization. All three allotropes are identified as mechanically (elastic constants) and dynamically (phonons) stable. The electronic band structures are characteristic of insulators with large band gaps of 4 to 5 eV, like diamond. From three different models evaluating Vickers hardness HV, all new carbon allotropes are identified as ultra-hard.

Structures and Electronic Properties of Graphene with Vacancy Defects

MRS Proceedings ◽

10.1557/opl.2014.500 ◽

2014 ◽

Vol 1658 ◽

Author(s):

J. Sugimoto ◽

K. Shintani

Keyword(s):

Electronic Properties ◽

First Principles ◽

Band Structures ◽

Electronic Band ◽

Vacancy Defects ◽

Electronic Band Structures ◽

Formation Energies

ABSTRACTThe structures and electronic properties of graphene with defects consisting of one to six atomic vacancies are investigated using first-principles calculation. All of the geometrically possible initial structures of a movacancy or a multivacancy in graphene are equilibrated. The formation energies and electronic band structures for the equilibrated defective structures are calculated. It is suggested non-zero bandgaps may be induced in graphene by introducing some types of monovacancy or multivacancy although further checks regarding supercell size are necessary to ensure the present results.

Predominance of non-adiabatic effects in zero-point renormalization of the electronic band gap

npj Computational Materials ◽

10.1038/s41524-020-00434-z ◽

2020 ◽

Vol 6 (1) ◽

Author(s):

Anna Miglio ◽

Véronique Brousseau-Couture ◽

Emile Godbout ◽

Gabriel Antonius ◽

Yang-Hao Chan ◽

...

Keyword(s):

Band Gap ◽

First Principles ◽

Large Scale ◽

Zero Point ◽

Band Gaps ◽

Electronic Band ◽

Electron Phonon Interaction ◽

Point Motion ◽

Optical Properties Of Materials ◽

Global Agreement

Abstract Electronic and optical properties of materials are affected by atomic motion through the electron–phonon interaction: not only band gaps change with temperature, but even at absolute zero temperature, zero-point motion causes band-gap renormalization. We present a large-scale first-principles evaluation of the zero-point renormalization of band edges beyond the adiabatic approximation. For materials with light elements, the band gap renormalization is often larger than 0.3 eV, and up to 0.7 eV. This effect cannot be ignored if accurate band gaps are sought. For infrared-active materials, global agreement with available experimental data is obtained only when non-adiabatic effects are taken into account. They even dominate zero-point renormalization for many materials, as shown by a generalized Fröhlich model that includes multiple phonon branches, anisotropic and degenerate electronic extrema, whose range of validity is established by comparison with first-principles results.

UNFOLDING BAND AND ABSORPTION ENERGY SHIFT OF Si-Ge NANO CRYSTALS FROM FIRST-PRINCIPLES CALCULATIONS

Communications in Physics ◽

10.15625/0868-3166/14942 ◽

2020 ◽

Vol 31 ◽

Author(s):

Van Quang Tran

Keyword(s):

Band Gap ◽

Brillouin Zone ◽

First Principles ◽

Density Functional ◽

Energy Shift ◽

Valence Band Maximum ◽

Band Structures ◽

Electronic Band ◽

Absorption Energy ◽

Physical properties of the Si1-xGex alloys (x being the composition of Ge) can be understood and predicted from their electronic band structures. In this paper, electronic band structures of the Si1-xGex alloys are calculated using the first-principles density functional theory. The supper cell approach employed in our calculations leads to the folding of electronic bands into the smaller Brillouin zone of the supercell, especially at the Γ point. This often leads to the misinterpretation that the materials have direct band gap. The problem can be resolved by the band unfolding technique which allows one to recover the primitive cell picture of band structure of Si1-xGex. As a result, unfolded electronic bands correctly show an indirect band gap with the valence band maximum (VBM) at the Γ point and the conduction band minimum (CBM) shifted away from Γ. The CBM is gradually shifted from a point along ΓX path (associated with Si) to the L point (associated with Ge) with the increased Ge composition x and the switching occurs at x in the range of 0.6~0.8 which is in accordance with the calculation using kp method. Moreover, the additional electron pockets appear and develop at Γ and L. This provides more comprehensive understanding for our recent experimental observations on the shift of the absorption energy assigned to E1 direct transitions within L and Γ points in the Brillouin zone of Si1-xGex alloy nanocrystals.

Strain-induced semimetal-to-semiconductor transition and indirect-to-direct band gap transition in monolayer 1T-TiS2

RSC Advances ◽

10.1039/c5ra16877e ◽

2015 ◽

Vol 5 (102) ◽

pp. 83876-83879 ◽

Cited By ~ 23

Author(s):

Chengyong Xu ◽

Paul A. Brown ◽

Kevin L. Shuford

Keyword(s):

Band Gap ◽

Electronic Properties ◽

Plane Strain ◽

Material Properties ◽

First Principles ◽

Tensile Strain ◽

First Principles Calculations ◽

Direct Band Gap ◽

Direct Band ◽

Uniform Plane

We have investigated the effect of uniform plane strain on the electronic properties of monolayer 1T-TiS2using first-principles calculations. With the appropriate tensile strain, the material properties can be transformed from a semimetal to a direct band gap semiconductor.

First-principles investigation of the electronic band structures and optical properties of quaternary ABaMQ4 (A = Rb, Cs; M = P, V; and Q = S) metal chalcogenides

International Journal of Modern Physics B ◽

10.1142/s021797921850337x ◽

2018 ◽

Vol 32 (30) ◽

pp. 1850337

Author(s):

Shahid Ullah ◽

Hayat Ullah ◽

Abdullah Yar ◽

Sikander Azam ◽

A. Laref

Keyword(s):

Optical Properties ◽

First Principles ◽

Density Functional ◽

Correlation Energy ◽

Electronic Charge ◽

Electromagnetic Spectrum ◽

Metal Chalcogenides ◽

Electronic Band ◽

Charge Densities ◽

In this paper, we study the optoelectronic properties of quaternary metal chalcogenide semiconductor ABaMQ4 (A = Rb, Cs; M = P, V; and Q = S) compounds using state-of-the-art density functional theory (DFT) with TB-mBJ approximation for the treatment of exchange-correlation energy. In particular, the electronic and optical properties of the relaxed geometries of these compounds are investigated. Our first-principles ab-initio calculations show that the CsBaPS4 and RbBaPS4 compounds have direct bandgaps whereas the CsBaVS4 compound exhibits indirect bandgap nature. Importantly, the theoretically calculated values of the bandgaps of the compounds are consistent with experiment. Furthermore, our analysis of the electronic charge densities of these compounds indicates that the above quaternary chalcogenides have mixed covalent and ionic bonding characters. The effective masses of these compounds are also calculated which provide very useful information about the band structure and transport characteristics of the investigated compounds. Similarly, high absorptivity in the visible and ultraviolet regions of the electromagnetic spectrum possibly predicts and indicates the importance of these materials for potential optoelectronic applications in this range.