scholarly journals Strain-Mediated Stability of Structures and Electronic Properties of ReS2, Janus ReSSe, and ReSe2 Monolayers

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Jia-Qi Zong ◽  
Shu-Feng Zhang ◽  
Wei-Xiao Ji ◽  
Chang-Wen Zhang ◽  
Ping Li ◽  
...  
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Electronic Materials ◽  
Bond Angle ◽  
Compressive Strain ◽  
Functional Approach ◽  
The Stability ◽  
Stability Of Structures

Monolayers of transition metal ReX2 and ReSX (X=S, Se) have been proposed as new electronic materials for nanoscale devices. In this paper, there are three structures: ReS2, Janus ReSSe, and ReSe2. Based on the first-principles theory, we analyzed the structures, electronic properties, and Fermi speed. Remarkably, we studied the stability of structures of ReS2, Janus ReSSe, and ReSe2 monolayers under biaxial tensile and compressive strain by density functional approach. It is worth noting that when the strain changes, not only the band gap changes but also the band gap properties (direct and indirect) also change. The bond gaps decrease with the increase of tensile strain and compressive strain; Moreover, when the strain is greater than 0, the bond angle decreases as the strain increases, and when the strain is less than 0, the bond angle increases as the strain increases.

STRAIN-TUNABLE BAND GAP OF BC3 SHEET: A FIRST-PRINCIPLES INVESTIGATION

2013 ◽  
Vol 27 (15) ◽  
pp. 1350110 ◽  
Author(s):  
GANG LIU ◽  
MU SHENG WU ◽  
CHU YING OUYANG ◽  
BO XU
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Tensile Strain ◽  
Compressive Strain ◽  
Valence Band Maximum ◽  
Functional Theory ◽  
Band Maximum ◽  
Tunable Band Gap

The effect of strain on the electronic properties of BC 3 sheet was studied by using first-principles density functional theory. It is found that the band gap of BC 3 sheet increases gradually when the applied tensile strain ranges from 0% to 12.5%. While the band gap decreases as the compressive strain is applied, especially resulting in the semiconductor-metal transition at some strain. Further analysis shows that the change of band gap mainly results from the variation of the energy of valence band maximum (VBM), which is related to the strength of the bonding state. The proposed mechanical control of the electronic properties will widen the application of BC 3 sheet in future nanotechnology.

Amorphous Semiconductors Studied by First-principles Simulations: Structure and Electronic Properties

2009 ◽  
Vol 1153 ◽  
Author(s):  
Karol Jarolimek ◽  
Robert A. de Groot ◽  
Gilles A. de Wijs ◽  
Miro Zeman
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Large Cell ◽  
Band Gap Energy ◽  
Amorphous Semiconductors ◽  
Structural Defects ◽  
Defect States ◽  
Wide Range

AbstractAtomistic models of amorphous solids enable us to study properties that are difficult to address with experimental methods. We present a study of two amorphous semiconductors with a great technological importance, namely a- Si:H and a-SiN:H. We use first-principles density functional theory (DFT), i.e. the interatomic forces are derived from basic quantum mechanics, as only that provides accurate interactions between the atoms for a wide range of chemical environments (e.g. brought about by composition changes). This type of precision is necessary for obtaining the correct short range order. Our amorphous samples are prepared by a cooling from liquid approach. As DFT calculations are very demanding, typically only short simulations can be carried out. Therefore most studies suffer from a substantial amount of defects, making them less useful for modeling purposes. We varied the cooling rate during the thermalization process and found it has a considerable impact on the quality of the resulting structure. A rate of 0.02 K/fs proves to be sufficient to prepare realistic samples with low defect concentrations. To our knowledge these are the first calculations that are entirely based on first-principles and at the same time are able to produce defect-free samples. Because of the high computational load also the size of the systems has to remain modest. The samples of a-Si:H and a-SiN:H contain 72 and 110 atoms, respectively. To examine the convergence with cells size, we utilize a large cell of a-Si:H with a total of 243 atoms. As we obtain essentially the same structure as with the smaller sample, we conclude that the use of smaller cells is justified. Although creating structures without any defects is important, on the other hand a small number of defects can give valuable information about the structure and electronic properties of defects in a-Si:H and a-SiN:H. In our samples we observe the presence of both the dangling bond (undercoordinated atom) and the floating bond (over-coordinated atom). We relate structural defects to electronic defect states within the band gap. In a-SiN:H the silicon-silicon bonds induce states at the valence and conduction band edges, thus decreasing the band gap energy. This finding is in agreement with measurements of the optical band gap, where increasing the nitrogen content increases the band gap.

First-principles study of the stability of silicane and germanane under strain

2014 ◽  
Vol 28 (17) ◽  
pp. 1450138 ◽  
Author(s):  
T. Y. Du ◽  
J. Zhao ◽  
G. Liu ◽  
J. X. Le ◽  
B. Xu
Keyword(s):  
First Principles ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Tensile Strain ◽  
Helmholtz Free Energy ◽  
Compressive Strain ◽  
Specific Capacity ◽  
Biaxial Strain ◽  
Functional Theory ◽  
The Stability

In this paper, we investigate the structural stability of silicane and germanane under biaxial strain by employing the lattice dynamics calculations within the frame of density functional theory. Our results show that silicane and germanane become unstable even under 1% compressive strain, while maintaining stable under tensile strain. Further calculations about the thermodynamical properties of silicane and germanane show that the phonon contribution to Helmholtz free energy, entropy and specific capacity are insensitive to the tensile strain.

scholarly journals A first-principle study on the electronic properties of substitutionally Cu (I, II)-doped LiNbO3

2018 ◽  
Vol 08 (01) ◽  
pp. 1820002 ◽  
Author(s):  
Xiaobin Liu ◽  
Wenxiu Que ◽  
Yucheng He ◽  
Huanfu Zhou
Keyword(s):  
Band Structure ◽  
Band Gap ◽  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
First Principles Calculations ◽  
Density Of State ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Small Band

The electronic properties of Cu-doped lithium niobate (LiNbO3) systems are investigated by first-principles calculations. In this work, we focus on substitutionally Cu[Formula: see text]Li-doped LiNbO3 system with cuprous and cupric doping, which corresponds to the Li[Formula: see text]Cu[Formula: see text]NbO3 and Li[Formula: see text]Cu[Formula: see text]NbO3 [abbreviated as (Li, Cu I)NbO3 and (Li, Cu II)NbO3]. The density functional theory (DFT) calculations show that the electronic property of LiNbO3 is completely different from (Li, Cu I)NbO3 and (Li, Cu II)NbO3. The calculated band structure and density of state (DOS) of (Li, Cu I)NbO3 show a small band gap of 1.34[Formula: see text]eV and the top of valance band (VB) is completely composed of a doping energy level originating from Cu 3d filled orbital. However, the calculated band structure and DOS of (Li, Cu II)NbO3 show a relatively large band gap of 2.22[Formula: see text]eV and the top of VB is mainly composed of Cu 3d unfilled orbital and O 2p orbital.

scholarly journals Strain Induced Tunability of the Electronic Properties of SrTiO3 Interfaces

2019 ◽  
Author(s):  
Zhenyun Lan ◽  
Tejs Vegge ◽  
Ivano E. Castelli
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Density Functional ◽  
Axial Strain ◽  
Compressive Strain ◽  
Conduction Band Edge ◽  
Biaxial Strain ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
New Perspective

SrTiO 3 (STO) films are widely used as substrates in oxide devices. Although STO is one of the most studied materials, both experimentally and computationally, the effect of strain at the interface is almost completely ignored. In this work, we perform Density Functional Theory (DFT) calculations using the SCAN meta-GGA exchange-correlation functional to study the effect of uniaxial- and biaxial-strain on structural and electronic properties of STO interfaces. We find that under tensile uniaxial-strain, the band gap increases significantly, as a consequence of a large tilting in the octahedra. On the other side, under compression, the band gap is almost constant. Similar effects are seen for tensile biaxial strain, while for compressive strain, the gap first increases and then decreases, due to the temporary appearance of a polar distortion. In addition, we observe an orbital inversion at the conduction-band edge under different uni/bi-axial-strain conditions. This work provides a new perspective of the use of strain to modulate the structural and electronic properties of perovskite film materials for multiple applications.

scholarly journals Strain Induced Tunability of the Electronic Properties of SrTiO3 Interfaces

2019 ◽  
Author(s):  
Zhenyun Lan ◽  
Tejs Vegge ◽  
Ivano E. Castelli
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Density Functional ◽  
Axial Strain ◽  
Compressive Strain ◽  
Conduction Band Edge ◽  
Biaxial Strain ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
New Perspective

SrTiO 3 (STO) films are widely used as substrates in oxide devices. Although STO is one of the most studied materials, both experimentally and computationally, the effect of strain at the interface is almost completely ignored. In this work, we perform Density Functional Theory (DFT) calculations using the SCAN meta-GGA exchange-correlation functional to study the effect of uniaxial- and biaxial-strain on structural and electronic properties of STO interfaces. We find that under tensile uniaxial-strain, the band gap increases significantly, as a consequence of a large tilting in the octahedra. On the other side, under compression, the band gap is almost constant. Similar effects are seen for tensile biaxial strain, while for compressive strain, the gap first increases and then decreases, due to the temporary appearance of a polar distortion. In addition, we observe an orbital inversion at the conduction-band edge under different uni/bi-axial-strain conditions. This work provides a new perspective of the use of strain to modulate the structural and electronic properties of perovskite film materials for multiple applications.

The effect of impurities in ultra-thin hydrogenated silicene and germanene: a first principles study

2015 ◽  
Vol 17 (34) ◽  
pp. 22210-22216 ◽  
Author(s):  
Caroline J. Rupp ◽  
Sudip Chakraborty ◽  
Rajeev Ahuja ◽  
Rogério J. Baierle
Keyword(s):  
Density Functional Theory ◽  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Spin Polarized ◽  
Effect Of Impurities ◽  
The Stability ◽  
Correlation Term

Spin polarized density functional theory within the GGA–PBE and HSE06 approach for the exchange correlation term has been used to investigate the stability and electronic properties of nitrogen and boron impurities in single layers of silicane and germanane.

scholarly journals AB INITIO STUDY OF SIZE AND STRAIN EFFECTS ON THE ELECTRONIC PROPERTIES OF Si NANOWIRES

2009 ◽  
Vol 01 (03) ◽  
pp. 483-499 ◽  
Author(s):  
X.-H. PENG ◽  
A. ALIZADEH ◽  
S. K. KUMAR ◽  
S. K. NAYAK
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Effective Mass ◽  
Density Functional ◽  
Compressive Strain ◽  
Si Nanowires ◽  
Functional Theory ◽  
Strain Effects ◽  
Size Dependent ◽  
Effective Masses

We have applied density-functional theory (DFT) based calculations to investigate the size and strain effects on the electronic properties, such as band structures, energy gaps and effective masses of the electron and the hole, in Si nanowires along the 〈110〉 direction with diameters up to 5 nm. Under uniaxial strain, we find that the band gap varies with strain and this variation is size dependent. For the 1–2 nm wire, the band gap is a linear function of strain, while for the 2–4 nm wire the gap variation with strain shows nearly parabolic behaviour. This size dependence of the gap variation with strain is explained on the basis of orbital characters of the band edges. In addition we find that the expansive strain increases the effective mass of the hole, while compressive strain increases the effective mass of the electron. The study of size and strain effects on effective masses shows that effective masses of the electron and the hole can be reduced by tuning the diameter of the wire and applying appropriate strain.

scholarly journals Stability, Elastic and Electronic Properties of Ta2N by First-Principles Calculations

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 445
Author(s):  
Longpeng Zhu ◽  
Jiong Wang ◽  
Chenchen Dong ◽  
Yong Du ◽  
Shun-Li Shang ◽  
...  
Keyword(s):  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Partial Density ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Charge Density Difference ◽  
Resistance To Deformation ◽  
The Stability ◽  
The Enthalpy Of Formation

Owing to exploring the influence of the N atoms ordering in Ta2N compounds on their properties, the stability, elastic, and electronic properties of Ta2N compounds (Ta2N-I: P3¯ml and Ta2N-II: P3¯1m) were investigated using first-principles calculations based on density functional theory. Ta2N-II is energetically favorable according to the enthalpy of formation. Elastic constants were employed to reveal the stronger resistance to deformation, but weaker anisotropy, in Ta2N-II. A ductile-brittle transition was found between Ta2N-I (ductile) and Ta2N-II (brittle). The partial density of states showed a stronger orbital hybridization of Ta-d and N-p in Ta2N-II, resulting in stronger covalent bonding. The charge density difference illustrated the interaction of the Ta-N bond and electron distribution of Ta2N.

Sign in / Sign up

Export Citation Format

Share Document