ELECTRONIC BAND STRUCTURE, OPTICAL, THERMAL AND BONDING PROPERTIES OF XMg2O4(X = Si, Ge) SPINEL COMPOUNDS

2013 ◽  
Vol 27 (18) ◽  
pp. 1350082 ◽  
Author(s):  
F. SEMARI ◽  
T. OUAHRANI ◽  
H. KHACHAI ◽  
R. KHENATA ◽  
M. RABAH ◽  
...  
Keyword(s):  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Theoretical Data ◽  
Debye Model ◽  
Ionic Character ◽  
Full Potential ◽  
Electronic Band ◽  
Spinel Compounds ◽  
Bonding Properties

Bonding nature as well as structural, optoelectronic and thermal properties of the cubic X Mg 2 O 4(X = Si , Ge ) spinel compounds have been calculated using a full-potential augmented plane-wave plus local orbitals (FP-APW+lo) method within the density functional theory. The exchange-correlation potential was treated with the PBE-GGA approximation to calculate the total energy. Moreover, the modified Becke–Johnson potential (TB-mBJ) was also applied to improve the electronic band structure calculations. The computed ground-state parameters (a, B, B′ and u) are in excellent agreements with the available theoretical data. Calculations of the electronic band structure and bonding properties show that these compounds have a direct energy band gap (Γ-Γ) with a dominated ionic character and the TB-mBJ approximation yields larger fundamental band gaps compared to those obtained using the PBE-GGA. Optical properties such as the complex dielectric function ε(ω), reflectivity R(ω) and energy loss function L(ω), for incident photon energy up to 40 eV, have been predicted. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the effects of pressure P and temperature T on the thermal expansion coefficient, Debye temperature and heat capacity for the considered compounds are investigated for the first time.

BAND STRUCTURE, HARDNESS, THERMODYNAMIC AND OPTICAL PROPERTIES OF SUPERCONDUCTING Nb2AsC, Nb2InC AND Mo2GaC

2013 ◽  
Vol 02 (02) ◽  
pp. 1350007 ◽  
Author(s):  
M. A. HADI ◽  
M. S. ALI ◽  
S. H. NAQIB ◽  
A. K. M. A. ISLAM
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Vickers Hardness ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Population Analysis ◽  
Debye Model ◽  
Electronic Band ◽  
Specific Heats ◽  
First Time

First-principles investigation of the geometry, electronic band structure, Vickers hardness, thermodynamic and optical properties of three superconducting MAX compounds Nb 2 AsC , Nb 2 InC and Mo 2 GaC have been carried out by the plane-wave pseudopotential method based on density functional theory (DFT) implemented in the CASTEP code. The theoretical Vickers hardness has been studied by means of Mulliken bond population analysis and electronic densities of states. The thermodynamic properties such as the temperature and pressure dependent bulk modulus, Debye temperature, specific heats and thermal expansion coefficient of the three 211 MAX phases are derived from the quasi-harmonic Debye model with phononic effect for the first time. Furthermore, all the optical properties are determined and analyzed for the first time for two different polarization directions. The theoretical findings are compared with relevant experiments (where available) and the various implications are discussed in details.

The Structural, Electronic, Optical and Thermo-Electric Properties of Oxynitride Perovskite CaTaO2N

SPIN ◽  
2020 ◽  
Vol 10 (01) ◽  
pp. 2050007
Author(s):  
K. Hocine ◽  
O. Cheref ◽  
K. Bettine ◽  
D. Rached ◽  
S. Benalia ◽  
...  
Keyword(s):  
Band Structure ◽  
Figure Of Merit ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Structural Parameters ◽  
Electric Properties ◽  
Partial Density ◽  
Full Potential ◽  
Thermo Electric ◽  
Electronic Band

In this study, we carried out ab-initio calculations of structural, electronic, optical and thermo-electric properties of CaTaO2N compound in Pnma orthorhombic structure, using the full-potential linearized augmented plane wave method (FP-LAPW), within the framework of density functional theory (DFT). The calculated structural parameters are found to be in good agreement with the experimental results. Moreover, we have studied the electronic band structure, total and partial density of states in order to explain the origin of band gaps and the nitrogen anion contribution in the valence and the conduction bands. The CaTaO2N band structure has shown a direct band gap in the direction [Formula: see text] (with the value 2.32[Formula: see text]eV). The optical properties represented by the dielectric functions for CaTaO2N compound have revealed that the Pnma structure absorbs the light at a large window in the edge UV-Vis regions. In order to explain the thermo-electric properties, we have calculated Seebeck coefficient, electrical conductivity, thermal conductivity and the factor figure of merit in this temperature range 100–1000 K. The factor figure of mérit (ZT) of CaTaO2N takes a maximum value of 0.775 at [Formula: see text][Formula: see text]K.

DFT-BASEDAB INITIOSTUDY OF THE ELECTRONIC AND OPTICAL PROPERTIES OF CESIUM BASED FLUORO-PEROVSKITECsMF3(M = CaANDSr)

2012 ◽  
Vol 26 (32) ◽  
pp. 1250199 ◽  
Author(s):  
M. HARMEL ◽  
H. KHACHAI ◽  
M. AMERI ◽  
R. KHENATA ◽  
N. BAKI ◽  
...  
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Theoretical Data ◽  
Full Potential ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Electronic And Optical Properties ◽  
Structure Density

Density functional theory (DFT) is performed to study the structural, electronic and optical properties of cubic fluoroperovskite AMF3( A = Cs ; M = Ca and Sr ) compounds. The calculations are based on the total-energy calculations within the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential is treated by local density approximation (LDA) and generalized gradient approximation (GGA). The structural properties, including lattice constants, bulk modulus and their pressure derivatives are in very good agreement with the available experimental and theoretical data. The calculations of the electronic band structure, density of states and charge density reveal that compounds are both ionic insulators. The optical properties (namely: the real and the imaginary parts of the dielectric function ε(ω), the refractive index n(ω) and the extinction coefficient k(ω)) were calculated for radiation up to 40.0 eV.

Ab-Initio Prediction of Intrinsic Half-Metallicity in Binary Alkali–Metal Chalcogenides: KX (X=S, Se and Te)

SPIN ◽  
2018 ◽  
Vol 08 (04) ◽  
pp. 1850020 ◽  
Author(s):  
N. Abbouni ◽  
S. Amari ◽  
H. Sadouki ◽  
A. Belkadi ◽  
Y. Zaoui ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Density Functional ◽  
Correlation Energy ◽  
Electronic Band Structure ◽  
Theoretical Data ◽  
Stable Phase ◽  
Full Potential ◽  
Metal Chalcogenides ◽  
Half Metallicity ◽  
Electronic Band

First-principles full-potential linearized augmented plane-wave method based on density functional theory is used to investigate the structural, electronic and magnetic properties of KX ([Formula: see text], Se and Te) binary alkali–metal chalcogenides compounds. These compounds in different crystalline phases, NaCl (B1), CsCl (B2), ZB (B3), NiAs (B8[Formula: see text], WZ (B4) and Pnma, were calculated within the generalized gradient approximation (GGA-PBE) and the modified Becke–Johnson approach (mBJ-GGA-PBE) for the exchange–correlation energy and potential. We found that the most stable phase for the KX binary compounds is the nonmagnetic Pnma phase. The calculated lattice parameters, bulk moduli, their first-pressure derivatives and internal parameters are in good agreement with the other theoretical data. The electronic band structure and density of states show that half-metallic and magnetic character arises, which can be attributed to the presence of spin-polarized [Formula: see text] orbitals in the group VI elements. KX ([Formula: see text], Se and Te) compounds, except for KSe and KTe in the CsCl and NiAs phases, show HM character in all phases, with an integer magnetic moment of 1[Formula: see text][Formula: see text] per formula unit and HM gaps.

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.

First principles calculation of structural, electronic and optical properties of (001) and (110) growth axis (InN)/(GaN)n superlattices

2021 ◽  
Vol 67 (1 Jan-Feb) ◽  
pp. 7
Author(s):  
B. Bachir Bouiadjra ◽  
N. Mehnane ◽  
N. Oukli
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Scale Up ◽  
Energy Scale ◽  
First Principles Calculation ◽  
Full Potential ◽  
Electronic Band ◽  
Electronic And Optical Properties ◽  
Growth Axis

Based on the full potential linear muffin-tin orbitals (FPLMTO) calculation within density functional theory, we systematically investigate the electronic and optical properties of (100) and (110)-oriented (InN)/(GaN)n zinc-blende superlattice with one InN monolayer and with different numbers of GaN monolayers. Specifically, the electronic band structure calculations and their related features, like the absorption coefficient and refractive index of these systems are computed over a wide photon energy scale up to 20 eV. The effect of periodicity layer numbers n on the band gaps and the optical activity of (InN)/(GaN)n SLs in the both  growth axis (001) and (110) are examined and compared. Because of prospective optical aspects of (InN)/(GaN)n such as light-emitting applications, this theoretical study can help the experimental measurements.

Ab-Initio Investigation of Strain Effects on the Physical Properties of PdVTe Alloy

2021 ◽  
Author(s):  
Khodja Djamila ◽  
Djaafri Tayeb ◽  
Djaafri Abdelkader ◽  
Bendjedid Aicha ◽  
Hamada Khelifa ◽  
...  
Keyword(s):  
Optical Properties ◽  
Density Of States ◽  
Phonon Dispersion ◽  
Electronic Band Structure ◽  
Debye Model ◽  
Full Potential ◽  
Electronic Band ◽  
Metallic Behavior ◽  
Strain Effects ◽  
Half Metallic

The investigations of the strain effects on magnetism, elasticity, electronic, optical and thermodynamic properties of PdVTe half-Heusler alloy are carried out using the most accurate methods to electronic band structure, i.e. the full-potential linearized augmented plane wave plus a local orbital (FP-LAPW + lo) approach. The analysis of the band structures and the density of states reveals the Half-metallic behavior with a small indirect band gap Eg of 0.51 eV around the Fermi level for the minority spin channels. The study of magnetic properties led to the predicted value of total magnetic moment µtot = 3µB, which nicely follows the Slater–Pauling rule µtot = Zt -18. Several optical properties are calculated for the first time and the predicted values are in line with the Penn model. It is shown from the imaginary part of the complex dielectric function that the investigated alloy is optically metallic. The variations of thermodynamic parameters calculated using the quasi-harmonic Debye model, accord well with the results predicted by the Debye theory. Moreover, the dynamical stability of the investigated alloy is computed by means of the phonon dispersion curves, the density of states, and the formation energies. Finally, the analysis of the strain effects reveals that PdVTe alloy preserves its ferromagnetic half metallic behavior, it remains mechanically stable, the ionic nature dominates the atomic bonding, and the thermodynamic and the optical properties keep the same features in a large interval of pressure.

DFT study of electronic and thermodynamic properties of gold-rich intermetallic compounds, Ce2Au2Cd and CeAu4Cd2

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jyoti Sagar ◽  
Reetu Singh ◽  
Vijay Kumar ◽  
Sanjay Kumar ◽  
Manish P. Singh ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Mechanical Strength ◽  
Intermetallic Compounds ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Debye Model ◽  
Effect Of Temperature ◽  
Mechanical Resistance ◽  
Electronic Band ◽  
High Mechanical Strength

Abstract Gold-rich rare earth intermetallic compounds (viz. Ce2Au2Cd and CeAu4Cd2) show unusual magnetic and physical properties, and they have extensive applications in electronic and mechanical industries due to their good electronic and thermal behavior with high mechanical strength. In the present research article, to take full advantage of technological importance of these materials, we have investigated the structural, electronic and thermodynamic properties of Ce2Au2Cd and CeAu4Cd2 ternary intermetallic compounds using density functional theory (DFT). The electronic band structure and density of state calculations show that Ce-f orbital electrons provide metallic character to both the compounds with strong hybridization of Au-p and Cd-p orbitals at the Fermi level. The effect of temperature has been studied on the various thermodynamic parameters using the quasi-harmonic Debye model. Thermodynamic properties show that CeAu4Cd2 compound has larger mechanical resistance (or high mechanical strength or hardness) and smaller randomness compared to Ce2Au2Cd with respect to temperature.

FIRST PRINCIPLE CALCULATION OF ELECTRONIC BAND STRUCTURE AND OPTICAL PROPERTIES OF KIO3

2009 ◽  
Vol 23 (10) ◽  
pp. 2405-2412
Author(s):  
HARUN AKKUS ◽  
BAHATTIN ERDINC
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Electronic Band ◽  
Principle Calculation ◽  
First Principle Calculation ◽  
Functional Methods ◽  
A Value ◽  
Direct Band

The electronic band structure and optical properties of the ferroelectric single crystal KIO 3 have been investigated using the density functional methods. The calculated band structure for KIO 3 evidences that the crystal has a direct band gap with a value of 2.83 eV. The structural optimization has been performed. The real and imaginary parts of dielectric function, energy-loss function for volume and surface, and refractive index are calculated along the crystallographic axes.

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