Electronic, Thermal, and Superconducting Properties of Metal Nitrides (MN) and Metal Carbides (MC) (M=V, Nb, Ta) Compounds by First Principles Studies

2015 ◽  
Vol 70 (9) ◽  
pp. 721-728
Author(s):  
G. Subhashree ◽  
S. Sankar ◽  
R. Krithiga
Keyword(s):  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Orbital Method ◽  
Superconducting Transition ◽  
Superconducting Properties ◽  
Transition Elements ◽  
Electronic Density ◽  
Electronic Band

AbstractStructural, electronic, and superconducting properties of carbides and nitrides of vanadium (V), niobium (Nb), and tantalum (Ta) (group V transition elements) have been studied by computing their electronic band structure characteristics. The electronic band structure calculations have been carried out based on the density functional theory (DFT) within the local density approximation (LDA) by using the tight binding linear muffin tin orbital method. The NaCl-type cubic structures of MN and MC (M=V, Nb, Ta) compounds have been confirmed from the electronic total energy minimum of these compounds. The ground state properties, such as equilibrium lattice constant (a0), bulk modulus (B), and Wigner–Seitz radius (S0) are determined and compared with available data. The electronic density of states reveals the metallic nature of the chosen materials. The electronic specific heat coefficient, Debye temperature, and superconducting transition temperature obtained from the band structure results are found to agree well with the earlier reported literature.

Superconducting properties of Mo3Os, Mo3Pt, Mo3Ir from first principle calculations

2014 ◽  
Vol 28 (30) ◽  
pp. 1450233 ◽  
Author(s):  
G. Subhashree ◽  
S. Sankar ◽  
R. Krithiga
Keyword(s):  
Band Structure ◽  
Electronic Band Structure ◽  
Tight Binding ◽  
Lattice Parameter ◽  
Orbital Method ◽  
First Principle ◽  
Superconducting Transition ◽  
Superconducting Properties ◽  
Electronic Band ◽  
First Principle Calculations

Self-consistent first principle calculations were carried out to investigate the structural, electronic, thermal and superconducting properties of Mo 3 X ( X = Os , Ir , Pt ) compounds of A15 phase that are studied by using the tight-binding linear muffin-tin orbital method. The E and k convergence have been checked to analyze the ground state properties. The band structure and DOS histograms are plotted from the calculated equilibrium lattice parameter. The bulk modulus (B B ), Debye temperature (θ D ), density of states (N(E F )), electron–phonon coupling constant (λ), superconducting transition temperature (Tc) and electronic specific heat coefficient (γ) have been calculated from the electronic band structure results. The calculated values have been compared with the available experimental results of literature.

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.

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.

scholarly journals Computational Investigation of the Electronic and Optical Properties of Planar Ga-Doped Graphene

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Nicole Creange ◽  
Costel Constantin ◽  
Jian-Xin Zhu ◽  
Alexander V. Balatsky ◽  
Jason T. Haraldsen
Keyword(s):  
Band Structure ◽  
Electron Density ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Impurity Scattering ◽  
Hole Doping ◽  
Electronic Band ◽  
Doped Graphene ◽  
Impurity Doping

We simulate the optical and electrical responses in gallium-doped graphene. Using density functional theory with a local density approximation, we simulate the electronic band structure and show the effects of impurity doping (0–3.91%) in graphene on the electron density, refractive index, optical conductivity, and extinction coefficient for each doping percentage. Here, gallium atoms are placed randomly (using a 5-point average) throughout a 128-atom sheet of graphene. These calculations demonstrate the effects of hole doping due to direct atomic substitution, where it is found that a disruption in the electronic structure and electron density for small doping levels is due to impurity scattering of the electrons. However, the system continues to produce metallic or semimetallic behavior with increasing doping levels. These calculations are compared to a purely theoretical 100% Ga sheet for comparison of conductivity. Furthermore, we examine the change in the electronic band structure, where the introduction of gallium electronic bands produces a shift in the electron bands and dissolves the characteristic Dirac cone within graphene, which leads to better electron mobility.

scholarly journals DFT COMPUTATION OF THE BAND STRUCTURE AND DENSITY OF STATE FOR ZnO HALITE STRUCTURE USING FHI-aims CODE.

2020 ◽  
Vol 4 (2) ◽  
pp. 490-498
Author(s):  
M. A. Adamu ◽  
K. Lawal ◽  
K. Lawal ◽  
A. Saminu
Keyword(s):  
Band Structure ◽  
Band Gap ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Research Work ◽  
Basis Sets ◽  
Band Structure Calculation ◽  
Density Of State ◽  
Electronic Band

This research work is on Density Functional Theory (DFT) within Local Density Approximation as parameterised by Perdew and Wang (pw-lda).The calculation was performed using Fritz Haber Institute Ab-initio Molecular Simulations (FHI-aims) code based on numerical atomic-centered orbital basis sets. The electronic band structure, density of state (DOS) and band gap energy were calculated for ZnO compound. The band structure and Density of States (DOS) diagrams are plotted from the calculated equilibrium lattice parameters. The experimentally lattice constant values were used to calculate the minimum total energy. The calculated electronic band structure results show that ZnO (Halite) is an indirect semiconductor with energy band gap of 0.89 eV. Hence, the HOMO is -0.863382 eV at L_symmetry point and LUMO is 0.0239417 eV at ᴦ- point. The DOS energy level within the compound shows considerable high state of electron occupation and the DOS observed around the Fermi level at zero level indicate that it has conducting properties. In general, FHI-aims code has shown better accuracy and prediction of band structure calculation within reasonable computational methods.

ELECTRONIC STRUCTURE, DIELECTRIC AND DYNAMICAL PROPERTIES OF ZINC-BLENDE AlN FROM FIRST PRINCIPLES CALCULATION

2007 ◽  
Vol 21 (26) ◽  
pp. 1775-1784
Author(s):  
HUAN-YOU WANG ◽  
HUI XU ◽  
JIAN-RONG XIAO ◽  
MINGJUN LI
Keyword(s):  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Lattice Parameter ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Plane Wave Method ◽  
Zinc Blende

We have performed density-functional perturbation calculation for zinc-blende AlN using the pseudopotential plane-wave method. The results obtained using both the local-density approximate (LDA) and the generalized-gradient approximate (GGA) for exchange-correlation functional are compared. The ground state properties and response function properties for zinc-blende AlN , including the electronic band structure, charge density, Born effective charge, dielectric constant and vibrational properties are reported. Our results are basically in agreement with experimental data and theoretical values available, but the bandgap is underestimated and the first optical mode in the phonon band structure is overestimated. This can be attributed to the underestimation of the lattice parameter and selection of the pseudopotential.

Effects of Morphology on the Electronic Properties of Hydrogenated Silicon Carbide Nanowires

2009 ◽  
Vol 5 ◽  
pp. 161-167 ◽  
Author(s):  
A. Miranda ◽  
J.L. Cuevas ◽  
A.E. Ramos ◽  
Miguel Cruz-Irisson
Keyword(s):  
Silicon Carbide ◽  
Band Structure ◽  
Band Gap ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Thickness Variation ◽  
Hydrogen Atoms ◽  
Electronic Density ◽  
Electronic Band ◽  
Sic Nanowires

The effects on the electronic band structure of hydrogenated cubic silicon carbide (-SiC) nanowires of changes in the diameter and morphology are studied using a semiempirical sp3s* tight-binding approach applied to a supercell model. The results of the calculation of the electronic band structure and electronic density of states obtained are compared with those calculated by density functional theory within local density approximation only for the bulk of -SiC. As boundary conditions, we passivated all the Si and C dangling bonds with hydrogen atoms. The results show that although surface morphology modifies the band gap, the change is more systematic with the thickness variation. The energy band gap increases with decreasing diameter in all cases because of quantum confinement, but the scaling is dependent on the morphology (cross-section) of the -SiC nanowires. Finally, the calculations show a consistent asymptotical behavior to the crystalline limit when the width of the wires enlarges.

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 An ab-initio study on structural, elastic, electronic, bonding, thermal, and optical properties of topological Weyl semimetal TaX (X = P, As)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. I. Naher ◽  
S. H. Naqib
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Fermi Level ◽  
Density Of States ◽  
Electronic Band Structure ◽  
Optical Parameters ◽  
Electronic Density ◽  
Electronic Band ◽  
Wide Range ◽  
Weyl Semimetals

AbstractIn recent days, study of topological Weyl semimetals have become an active branch of physics and materials science because they led to realization of the Weyl fermions and exhibited protected Fermi arc surface states. Therefore, topological Weyl semimetals TaX (X = P, As) are important electronic systems to investigate both from the point of view of fundamental physics and potential applications. In this work, we have studied the structural, elastic, mechanical, electronic, bonding, acoustic, thermal and optical properties of TaX (X = P, As) in detail via first-principles method using the density functional theory. A comprehensive study of elastic constants and moduli shows that both TaP and TaAs possesses low to medium level of elastic anisotropy (depending on the measure), reasonably good machinability, mixed bonding characteristics with ionic and covalent contributions, brittle nature and relatively high Vickers hardness with a low Debye temperature and melting temperature. The minimum thermal conductivities and anisotropies of TaX (X = P, As) are calculated. Bond population analysis supports the bonding nature as predicted by the elastic parameters. The bulk electronic band structure calculations reveal clear semi-metallic features with quasi-linear energy dispersions in certain sections of the Brillouin zone near the Fermi level. A pseudogap in the electronic energy density of states at the Fermi level separating the bonding and the antibonding states indicates significant electronic stability of tetragonal TaX (X = P, As).The reflectivity spectra show almost non-selective behavior over a wide range of photon energy encompassing visible to mid-ultraviolet regions. High reflectivity over wide spectral range makes TaX suitable as reflecting coating. TaX (X = P, As) are very efficient absorber of ultraviolet radiation. Both the compounds are moderately optically anisotropic owing to the anisotropic nature of the electronic band structure. The refractive indices are very high in the infrared to visible range. All the energy dependent optical parameters show metallic features and are in complete accord with the underlying bulk electronic density of states calculations.

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