Structural, Optoelectronic and Thermoelectric Properties of Ternary CaBe2X2 (X = N, P, As, Sb, Bi) Compounds

2018 ◽  
Vol 73 (10) ◽  
pp. 965-973 ◽  
Author(s):  
Abdul Ahad Khan ◽  
Aziz Ur Rehman ◽  
A. Laref ◽  
Masood Yousaf ◽  
G. Murtaza
Keyword(s):  
Band Gap ◽  
Thermoelectric Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Structural Parameters ◽  
Infrared Region ◽  
Ultraviolet Region ◽  
Thermo Electric ◽  
Electronic Band ◽  
Electron Charge Density

AbstractThe structural, electronic, optical and thermoelectric properties of ternary CaBe2X2 (X = N, P, As, Sb and Bi) have been investigated comprehensively for the first time using density functional theory. All the compounds are optimized to obtain their ground states. Computed structural parameters agree to the available experimental results. Electronic band structure calculations reveal the semiconducting nature of the compounds, while bang gap decreases by changing the anion X from N to Bi the band gap decreases. In the valence band, major contribution is due to X-p state, while in conduction band (CB) the major contribution is mainly due to the Ca-d state. Furthermore, electron charge density plots reveal ionic bonding character with small covalent bonding. Optical properties are calculated in detail. Static value of refractive index shows inverse variation with band gap. The refractive indices of these compounds are high in the infrared region and gradually decreased in the visible and ultraviolet region. The thermoelectric properties are studied using Boltzmann statistics through BoltzTraP code. High optical conductivity peaks and figure of merits (ZT) for compounds reveal that they are good candidates for the optoelectronics and thermo-electric devices.

First-principles study of electronic, optical and thermoelectric properties in cubic perovskite materials AgMO3 (M = V, Nb, Ta)

2014 ◽  
Vol 28 (10) ◽  
pp. 1450077 ◽  
Author(s):  
Asif Mahmood ◽  
Shahid M. Ramay ◽  
Hafiz Muhammad Rafique ◽  
Yousef Al-Zaghayer ◽  
Salah Ud-Din Khan
Keyword(s):  
Thermoelectric Properties ◽  
First Principles ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Structural Parameters ◽  
Full Potential ◽  
Electronic Band ◽  
Functional Theory ◽  
Perovskite Materials ◽  
Linearized Augmented Plane Wave

In this paper, first-principles calculations of structural, electronic, optical and thermoelectric properties of AgMO 3 ( M = V , Nb and Ta ) have been carried out using full potential linearized augmented plane wave plus local orbitals method ( FP - LAPW + lo ) and BoltzTraP code within the framework of density functional theory (DFT). The calculated structural parameters are found to agree well with the experimental data, while the electronic band structure indicates that AgNbO 3 and AgTaO 3 are semiconductors with indirect bandgaps of 1.60 eV and 1.64 eV, respectively, between the occupied O 2p and unoccupied d states of Nb and Ta . On the other hand, AgVO 3 is found metallic due to the overlapping behavior of states across the Fermi level. Furthermore, optical properties, such as dielectric function, absorption coefficient, optical reflectivity, refractive index and extinction coefficient of AgNbO 3 and AgTaO 3, are calculated for incident photon energy up to 50 eV. Finally, we calculate thermo power for AgNbO 3 and AgTaO 3 at fixed doping 1019 cm-3. Electron doped thermo power of AgNbO 3 shows significant increase over AgTaO 3 with temperature.

scholarly journals An ab-initio Investigation: The physical properties of ScIr-=SUB=-2-=/SUB=- Superconductor -=SUP=-*-=/SUP=-

2019 ◽  
Vol 61 (4) ◽  
pp. 659
Author(s):  
Uttam Kumar Chowdhury ◽  
Tapas Chandra Saha
Keyword(s):  
Physical Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Structural Parameters ◽  
Ultraviolet Region ◽  
Electronic Band ◽  
Cauchy Pressure ◽  
Pseudopotential Approach ◽  
First Time

AbstractUsing ab initio technique the physical properties of ScIr_2 superconductor have been investigated with T _c 1.03 K with a MgCu_2-type structure. We have carried out the plane-wave pseudopotential approach within the framework of the first-principles density functional theory (DFT) implemented within the CASTEP code. The calculated structural parameters confirm a good agreement with the experimental and other theoretical results. Using the Voigt-Reuss-Hill (VRH) averaging scheme the most important elastic properties including the bulk modulus B, shear modulus G , Young’s modulus E and Poisson’s ratio ν of ScIr_2 are determined. At ambient condition, the values of Cauchy pressure and Pugh’s ratio exhibit ductile nature of ScIr_2. The electronic and optical properties of ScIr_2 were investigated for the first time. The electronic band structure reveals metallic conductivity and the major contribution comes from Ir-5 d states. In the ultraviolet region the reflectivity is high up to 50 eV as evident from the reflectivity spectrum.

First-principles calculations on structure and electronic properties of α-zirconium hydrogen phosphate

MRS Advances ◽  
2019 ◽  
Vol 4 (50) ◽  
pp. 2699-2707
Author(s):  
V. W. Elloh ◽  
Soni Mishra ◽  
A. Yaya ◽  
Abhishek Kumar Mishra
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Semiconductor Device ◽  
Electronic Band Structure ◽  
Structural Parameters ◽  
Hydrogen Phosphate ◽  
Electronic Band ◽  
Potential Applications ◽  
Direct Band

AbstractLayered zirconium hydrogen phosphate intercalation compounds can be easily tuned, leading to potential applications in many fields, specifically by introducing them in different polymeric composites as nanofillers. Employing first-principles density functional theory based calculations, we have investigated ground state electronic structure properties of α-zirconium hydrogen phosphate (α-ZrP). We discuss the structure and electronic band structure, where projected density of states calculations have been discussed to understand the different atomic orbitals contributions to electronic bands. ZrP has numerous properties of interest for use in many semiconductor device structures, specifically, layered zirconium hydrogen phosphate has substantial promise for both optical devices and for high power electronics due to its large direct band gap. Our structural calculations suggest that layered zirconium hydrogen phosphate exhibits monoclinic structure. The calculated structural parameters and band gap are in good agreement with available experimental data.

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.

scholarly journals The structural, elastic, electronic and optical properties of MgCu under pressure: A first-principles study

2016 ◽  
Vol 30 (27) ◽  
pp. 1650199 ◽  
Author(s):  
Md. Afjalur Rahman ◽  
Md. Zahidur Rahaman ◽  
Md. Atikur Rahman
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Structural Parameters ◽  
Normal Pressure ◽  
Type Structure ◽  
Ultraviolet Region ◽  
Electronic Band ◽  
Electronic And Optical Properties

The effect of pressure on the structural, elastic and electronic properties of the intermetallic compound MgCu with a CsCl-type structure have been investigated using ab initio technique. The optical properties have been studied under normal pressure. We have carried out the plane-wave pseudopotential approach within the framework of the first-principles density functional theory (DFT) implemented within the CASTEP code. The calculated structural parameters show a good agreement with the experimental and other theoretical results. The most important elastic properties including the bulk modulus [Formula: see text], shear modulus [Formula: see text], Young’s modulus [Formula: see text] and Poisson’s ratio [Formula: see text] of the cubic-type structure MgCu are determined under pressure by using the Voigt–Reuss–Hill (VRH) averaging scheme. The results show that the MgCu intermetallic becomes unstable under pressure more than 15 GPa. The study of Cauchy pressure and Pugh’s ratio exhibit brittle nature of MgCu at ambient condition and the compound is transformed into ductile nature with the increase of pressure. For the first time we have investigated the electronic and optical properties of MgCu. The electronic band structure reveals metallic conductivity and the major contribution comes from Cu-[Formula: see text] states. Reflectivity spectrum shows that the reflectivity is high in the ultraviolet region up to 72 eV.

scholarly journals Structural, Electronic and Vibrational Properties of YAl3(BO3)4

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 545 ◽  
Author(s):  
Aleksandr S. Oreshonkov ◽  
Evgenii M. Roginskii ◽  
Nikolai P. Shestakov ◽  
Irina A. Gudim ◽  
Vladislav L. Temerov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Band Gap ◽  
Density Functional ◽  
Dielectric Material ◽  
Electronic Band Structure ◽  
Vibrational Properties ◽  
Electronic Band ◽  
Functional Theory ◽  
Dynamical Properties ◽  
Indirect Band Gap

The crystal structure of YAl3(BO3)4 is obtained by Rietveld refinement analysis in the present study. The dynamical properties are studied both theoretically and experimentally. The experimental Raman and Infrared spectra are interpreted using the results of ab initio calculations within density functional theory. The phonon band gap in the Infrared spectrum is observed in both trigonal and hypothetical monoclinic structures of YAl3(BO3)4. The electronic band structure is studied theoretically, and the value of the band gap is obtained. It was found that the YAl3(BO3)4 is an indirect band gap dielectric material.

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.

Theoretical Investigation on Electronic Properties of ZnO Crystals Using DFT-Based Calculation Method

2015 ◽  
Vol 1112 ◽  
pp. 41-44 ◽  
Author(s):  
Yudi Darma ◽  
Freddy Giovanni Setiawan ◽  
Muhammad Aziz Majidi ◽  
Andrivo Rusydi
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Valence Band Maximum ◽  
Band Gaps ◽  
Generalized Gradient ◽  
Strong Electron ◽  
Electronic Band ◽  
Rocksalt Structure

We study the electronic band structure and density of states (DOS) on ZnO material in various crystal structures : wurtzite (W), zincblende (ZB), and rocksalt (RS) phases. Calculations are based on Density Functional Theory (DFT) with Generalized Gradient Approximation (GGA) for exchange-correlation functional and Hubbard correction to consider the strong electron correlations in 3d orbitals. After structural optimization, GGA results show that wurtzite and zincblende structures have a direct band gap of 0.749 eV and 0.637 eV, respectively, whereas rocksalt structure has an indirect band gap of 0.817 eV. Symmetrical shape of total DOS for spin up and spin down electrons indicates a zero total magnetic moment. For all ZnO structures, the upper valence band is formed by hybridization among O 2p and Zn 3d orbitals, while lower valence and conduction band are primarily filled by O 2s and Zn 4s, respectively. The GGA+U approach is found to improve the calculated band gaps and correct the position of Zn 3d state below Valence Band Maximum (VBM). From GGA+U, the band gaps for W-ZnO, ZB-ZnO, and RS-ZnO are 1.12 eV, 1.00 eV, and 1.11 eV, respectively.

Electronic structure, optical and thermodynamic properties of ternary hydrides MBeH3 (M = Li, Na, and K)

2016 ◽  
Vol 94 (9) ◽  
pp. 865-876 ◽  
Author(s):  
Dj Guendouz ◽  
Z. Charifi ◽  
H. Baaziz ◽  
T. Ghellab ◽  
N. Arikan ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Thermodynamic Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Debye Model ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Electron Charge Density ◽  
Principal Aspect

Electronic band structure, optical and thermodynamic properties of ternary hydrides MBeH3 (M = Li, Na, and K) were studied using ab initio density functional theory (DFT). The effect of the adopted approximation to the exchange-correlation functional of the DFT is explicitly investigated by considering four different expressions of two different classes (local-density approximation and generalized-gradient approximation). The calculated magnitude of B classifies MBeH3 (M = Li, Na, and K) as easily compressible materials. The bonding interaction in these compounds is quite complicated. The interaction between M and BeH6 is ionic and that between Be and H comprises both ionic and covalent characters. The electronic structure of the complex hydride was investigated by calculating the partial and total densities of states, and electron charge density distribution. Large gaps in the density of states appear at the Fermi energy of LiBeH3, NaBeH3, and KBeH3 indicating that these classes of hydrides are insulators. Optical properties, including the dielectric function, reflectivity, and absorption coefficient, each as a function of photon energy, are calculated and show an optical anisotropy for LiBeH3 and KBeH3. Through the quasi-harmonic Debye model, in which the phononic effects are considered, temperature dependence of volume V(T), bulk modulus B(T), and thermal expansion coefficient α(T), constant-volume and constant-pressure specific heat (Cv and Cp) and Debye temperature ΘD, the entropy S, and the Grüneisen parameter γ were calculated at wide pressure and temperature ranges. The principal aspect of the obtained results is the close similarity of MBeH3 (M = Li, Na, and K) compounds.

Effect of Pressure on Structural, Electronic and Elastic Properties of Cubic (Pm3m) SnTiO3 Using First Principle Calculation

2012 ◽  
Vol 501 ◽  
pp. 342-346 ◽  
Author(s):  
M.F.M. Taib ◽  
M.K. Yaakob ◽  
Amreesh Chandra ◽  
Abdul Kariem Mohd Arof ◽  
M.Z.A. Yahya
Keyword(s):  
Band Gap ◽  
Elastic Properties ◽  
Elastic Constants ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Perovskite Oxide ◽  
First Principles Calculation ◽  
Cubic Phase ◽  
Electronic Band

The electronic band structure, density of state and elastic properties of lead-free perovskite oxide SnTiO3 (ST) were investigated by employing first principles calculation using the Density Functional Theory (DFT) within local density approximation (LDA). The energy band gap was calculated from the separation between the Ti 3d (conduction band) and the maximum of O 2p (valence band). This gives an indirect band gap of 2.36 eV. The elastic constants and their pressure dependence were calculated up to 30 GPa and the independent elastic constants (C11, C12, and C44), bulk modules, B were obtained and analyzed. The results showed that SnTiO3 have a mechanical stability in cubic phase (Pm3m).

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