scholarly journals Theoretical study of the band structure of 2H-SiC and 4H-SiC of silicon carbide polytypes

2021 ◽  
Vol 24 (2) ◽  
pp. 23706
Author(s):  
A. V. Sinelnik ◽  
A. V. Semenov
Keyword(s):  
Silicon Carbide ◽  
Band Structure ◽  
Density Functional ◽  
Dft Method ◽  
Generalized Gradient ◽  
Gw Approximation ◽  
Electronic Band ◽  
Functional Theory ◽  
Optimum Approach ◽  
Experimental Values

We have studied the electronic band properties of 2H-SiC and 4H-SiC silicon carbide polytypes. The structures of the electronic bands and density of state (DOS) using ab initio Density Functional Theory (DFT) were calculated for the first Brillouin zone both in the generalized gradient approximation and taking into account quasiparticle effects according to the GW scheme. The calculated bandgaps obtained using the GW approximation Eg2H-SiC = 3.17 eV and Eg4H-SiC = 3.26 eV agree well with experimental values. The shape and values of total DOS are within agreement with calculations performed by other authors. The calculated total energy values for 2H-SiC and 4H-SiC were close, but they satisfy the condition E2H > E4H, which implies that the 4H-SiC structure is more stable than 2H-SiC. Our calculations of the band structure and DOS of 2H-SiC and 4H-SiC by the DFT method showed that the application of the GW approximation is an optimum approach to the study of the electronic structure of 2H-SiC and 4H-SiC polytypes.

THEORETICAL STUDY OF THE BAND GAP OF SrSe AND SrTe IN GW APPROXIMATION

2011 ◽  
Vol 25 (23) ◽  
pp. 1905-1914
Author(s):  
XIAO LING ZHU ◽  
HONG ZHANG ◽  
XIN LU CHENG
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Theoretical Study ◽  
Generalized Gradient ◽  
Gw Approximation ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Structural And Electronic Properties ◽  
Experimental Values ◽  
Interaction Approximation

Using the first-principles pseudopotential method within a generalized gradient approximation of the density functional theory, the structural and electronic properties of SrSe and SrTe have been studied. The calculated lattice parameters are in excellent agreement with experimental values, whereas the error in the minimum gap value is as high as 43.25% in SrSe . To get reliable band gap values of SrSe and SrTe , we employ the GW (G is the Green's function and W is the screened Coulomb interaction) approximation method. The result in GW approximation improves the band gap value of the SrSe greatly and agrees with the value of experimental measurement.

Ab initio calculation on the Optical Properties of AA- Stacked two dimensional Graphene, Silicene, Germanene, and Stanene

2018 ◽  
Vol 1 (1) ◽  
pp. 46-50
Author(s):  
Rita John ◽  
Benita Merlin
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Complex Refractive Index ◽  
Single Layer ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Wide Range ◽  
Optical Region

In this study, we have analyzed the electronic band structure and optical properties of AA-stacked bilayer graphene and its 2D analogues and compared the results with single layers. The calculations have been done using Density Functional Theory with Generalized Gradient Approximation as exchange correlation potential as in CASTEP. The study on electronic band structure shows the splitting of valence and conduction bands. A band gap of 0.342eV in graphene and an infinitesimally small gap in other 2D materials are generated. Similar to a single layer, AA-stacked bilayer materials also exhibit excellent optical properties throughout the optical region from infrared to ultraviolet. Optical properties are studied along both parallel (||) and perpendicular ( ) polarization directions. The complex dielectric function (ε) and the complex refractive index (N) are calculated. The calculated values of ε and N enable us to analyze optical absorption, reflectivity, conductivity, and the electron loss function. Inferences from the study of optical properties are presented. In general the optical properties are found to be enhanced compared to its corresponding single layer. The further study brings out greater inferences towards their direct application in the optical industry through a wide range of the optical spectrum.

scholarly journals Evolution of Dirac Cone in Disclinated Graphene

2018 ◽  
Vol 57 (2) ◽  
pp. 137-142 ◽  
Author(s):  
M.A. Rozhkov ◽  
A.L. Kolesnikova ◽  
I. Hussainova ◽  
M.A. Kaliteevskii ◽  
T.S. Orlova ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Band Structure ◽  
Density Functional ◽  
Md Simulation ◽  
Dirac Cone ◽  
Electronic Band ◽  
Functional Theory ◽  
Periodic Distribution ◽  
Electronic Band Structures

Abstract Graphene crystals, containing arrays of disclination defects, are modeled and their energies are calculated using molecular dynamics (MD) simulation technique. Two cases are analyzed in details: (i) pseudo-graphenes, which contain the alternating sign disclination ensembles and (ii) graphene with periodic distribution of disclination quadrupoles. Electronic band structures of disclinated graphene crystals are calculated in the framework of density functional theory (DFT) approach. The evolution of the Dirac cone and magnitude of band gap in the band structure reveal a dependence on the density of disclination quadrupoles and alternating sign disclinations. The electronic properties of graphene with disclination ensembles are discussed.

FIRST-PRINCIPLES STUDIES ON THE ELECTRONIC STRUCTURE OF LuPd2Si2

2009 ◽  
Vol 23 (32) ◽  
pp. 5929-5934 ◽  
Author(s):  
T. JEONG
Keyword(s):  
Band Structure ◽  
First Principles ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Spin Orbit Coupling ◽  
Electronic Band ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Structure Scheme

The electronic band structure of LuPd 2 Si 2 was studied based on the density functional theory within local density approximation and fully relativistic schemes. The Lu 4f states are completely filled and have flat bands around -5.0 eV. The fully relativistic band structure scheme shows that spin–orbit coupling splits the 4f states into two manifolds, the 4f7/2 and the 4f5/2 multiplet.

scholarly journals Ab-initio study of the orthorhombic ndmno3 perovskite

2014 ◽  
Vol 70 (a1) ◽  
pp. C1806-C1806
Author(s):  
Samir Bentata ◽  
Bouabdellah Bouadjemi ◽  
Tayeb Lantri ◽  
Wissem Benstaali
Keyword(s):  
Density Functional ◽  
Electronic Band Structure ◽  
Total Density ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Functional Theory ◽  
Half Metallic ◽  
Generalized Gradient Approximation ◽  
Ferromagnetic Ground State ◽  
Total Density Of States

We investigate the structural, electronic and magnetic properties of the orthorhombic Perovskite oxyde NdMnO3 through density-functional-theory (DFT) calculations using both generalized gradient approximation GGA+U, where U is on-site Coulomb interaction correction. The electronic band structure, the partial and total density of states (DOS) and the magnetic moment are determined. The results show a half-metallic ferromagnetic ground state for the orthorhombic NdMnO3.

Density Functional Calculations on Electronic and Magnetic Properties of Fe-Pt Systems

2005 ◽  
Vol 475-479 ◽  
pp. 3103-3106 ◽  
Author(s):  
You Song Gu ◽  
Jian He ◽  
Zhen Ji ◽  
Xiao Yan Zhan ◽  
Yue Zhang ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Moment ◽  
Electronic Structures ◽  
Density Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
Experimental Values ◽  
Pseudo Potential

The electronic structures and magnetic properties of Fe-Pt systems were calculated by CASTEP codes, which employed density functional theory, generalized gradient approximation (GGA), Perdew Burke Ernzerh exchange correlation, Pulay density-mixing scheme and Ultra Soft pseudo potential. The band structures and density of states (DOS) were calculated, together with band populations and magnetic properties. The calculated results of α-Fe show the validatiy of this method in predication magnetic properties. It is found that as the Pt concentration increases, Fe 4s and 3d electrons decrease while 4p electrons increase, and the magnetic moment of Fe atom increases. Pt atoms also contribute to the magnetic moment due to polarization. The calculated magnetization agrees with experimental values quite well.

Electronic Band Structure of Cubic Silicon Carbide Nanowires

2008 ◽  
Vol 600-603 ◽  
pp. 575-578 ◽  
Author(s):  
A. Miranda ◽  
A. Estrella Ramos ◽  
M. Cruz Irisson
Keyword(s):  
Silicon Carbide ◽  
Band Structure ◽  
Band Gap ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Thickness Variation ◽  
Hydrogen Atoms ◽  
Electronic Band ◽  
Cubic Silicon Carbide

In this work, the effects of the diameter and morphology on the electronic band structure of hydrogenated cubic silicon carbide (b-SiC) nanowires is studied by using a semiempirical sp3s* tight-binding (TB) approach applied to the supercell model, where the Si- and C-dangling bonds on the surface are passivated by hydrogen atoms. Moreover, TB results (for the bulk) are compared with density functional calculations in the local density approximation. The results show that though surface morphology modifies the band gap, the change is more systematic with the thickness variation. As expected, hydrogen saturation induces a broadening of the band gap energy because of the quantum confinement effect.

Atomic and Electronic Structure of LaAlO3 and LaAlO3:Mg from First-Principles Calculations

2009 ◽  
Vol 79-82 ◽  
pp. 1257-1260
Author(s):  
Li Guan ◽  
Li Tao Jin ◽  
Wei Zhang ◽  
Qiang Li ◽  
Jian Xin Guo ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Band Gap ◽  
Density Functional ◽  
Lattice Structure ◽  
Cell Structure ◽  
Functional Theory ◽  
Super Cell ◽  
Direct Band ◽  
Experimental Values

In the present paper, the lattice structure, band structure and density of state of LaAlO3 and LaAlO3:Mg are calculated by first-principle method based on density functional theory. Firstly, we select the different cutoff energy and k-point grid in the calculations, and obtain the most stable geometry structure of single crystal LaAlO3. The calculated lattice parameters are a=b=5.441 Å, c=13.266 Å, which matches with experimental values. To deeply understand the electronic structure of LaAlO3, a 2×1×1 super-cell structure is established and the doping concentration of Mg at Al sites is 25%. From the band structure and density of states, it can be seen that LaAlO3 has a direct band gap Eg=3.6 eV. However, LaAlO3:Mg has a larger band gap Eg=3.89 eV and the Fermi level enters into the valence band, which indicates the holes are introduced. The calculated results show that the conductivity of LaAlO3:Mg is better than pure LaAlO3, which is in good agreement with experimental results.

scholarly journals Intriguing electronic, optical and photocatalytic performance of BSe, M2CO2 monolayers and BSe–M2CO2 (M = Ti, Zr, Hf) van der Waals heterostructures

RSC Advances ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 42-52
Author(s):  
M. Munawar ◽  
M. Idrees ◽  
Iftikhar Ahmad ◽  
H. U. Din ◽  
B. Amin
Keyword(s):  
Density Functional Theory ◽  
Band Structure ◽  
Density Functional ◽  
Photocatalytic Performance ◽  
Electronic Band Structure ◽  
Van Der Waals ◽  
Density Functional Theory Calculations ◽  
Van Der Waals Heterostructures ◽  
Electronic Band ◽  
Functional Theory

Using density functional theory calculations, we have investigated the electronic band structure, optical and photocatalytic response of BSe, M2CO2 (M = Ti, Zr, Hf) monolayers and their corresponding BSe–M2CO2 (M = Ti, Zr, Hf) van der Waals heterostructures.

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