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Na0.5(Bi3/4RE1/4)0.5TiO3 (RENBT, RE = Nd, Gd, Dy, and Ho) compounds were investigated in the framework of first-principles calculations using the full potential linearized augmented plane wave (FP-LAPW) method based on the spin-polarized density functional theory implemented in the WIEN2k code. Combined charge density distribution and Ti K-edge X-ray absorption spectra revealed that the RENBT compositions with high polarization values were accompanied by a higher TiO6 distortion, DyNBT, and NdNBT compounds. The effect of the rare-earth elements on the polarization were confirmed experimentally with the collection of the hysteresis loops. The investigation of the electronic properties of the compounds highlighted the emergence of a magnetization owing to the 4f orbital effect of the rare-earth elements. Besides, the investigation of the chemical ordering showed a short-range chemical ordering for the pure composition and an increased A-site disorder for dysprosium doped NBT system. The increased disorder may speak for increased relaxor properties in the RE doped compositions.

An ab initio study using density functional theory (DFT) is carried out to explore the structural, electronic, and optical properties of vanadium gallate (VGaO3) and niobium gallate (NbGaO3). The structural properties of these compounds are determined by using the full-potential linearized augmented plane wave (FP-LAPW) technique as implemented in WIEN2k with a standard functional, i.e., the Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA). In addition, the local density approximation plus Hubbard parameter (LDA + U) is employed to calculate the electronic bandgap and total and partial density of states (TDOS and PDOS), to overcome the limitation of the PBE-GGA functional in terms of underestimation of the electronic bandgap. The values computed for the indirect bandgap of VGaO3 and NbGaO3 are 0.45 and 0.51 eV, respectively, indicating that both materials are semiconductors in nature. The PDOS of the studied materials reveal that 3d-states of vanadium atoms, 4d-states of niobium atoms, and 2p-states of oxygen atoms form the valence band. Moreover, the Kramer–Kronig relations are used to compute the optical properties of the title compounds. The dielectric functions, refractive index, optical conductivity, absorption coefficient, extinction coefficient, energy loss function, and reflectivity of these materials are also computed. The results for the studied properties reveal that NbGaO3 exhibits better properties than VGaO3 for use in optoelectronic applications.

The first principles calculations based on density functional theory computed in Wien2k package using full-potential linearized augmented-plane wave (FP-LAPW) method to explore the electronic and optical properties of CuCoMnZ (Z=Si, Sb, Sn) equiatomic quaternary Heusler alloys (QHAs). The exchange and correlation functional are dealt with in the frame work of generalized gradient approximation modified by Perdew–Burke–Ernzerhof. The electronic band structure of our QHAs in spin up and down channels showed the overlapping of valence states with conduction states, which confirms the metallic nature of our alloys. The optical properties, like refraction, reflectivity, complex dielectric function, optical conductivity, absorption and eloss are also investigated over the wide range of incident photon energies, which revealed the effectiveness of CuCoMnZ (Z=Si, Sn, Sb).

The electronic, magnetic, optical and transport properties of ZnFe2O4 compound are calculated using the density functional theory implemented on Wien2k code with GGA + U approximation. The results ...

In this paper, we report the results of first-principles calculations on the electronic structure of the superstoichiometric dihydrides TbH2.25 with space group symmetry I4/mmm. The calculations including structural relaxation are based on the DFT. The latter was implemented using the WIEN2k simulation code. The generalized gradient approximation (GGA) and local density approximation (LDA) were used for the exchange and correlation energy functionals. The structural and electronic properties of terbium superstoichiometric dihydrides with the tetragonal structure (I4/mmm) have been systematically investigated. The basic ground state properties (at 0 K) viz., lattice constants, bulk moduli and their pressure derivatives and total energies are calculated. The optimized unit-cell parameters under relaxation fit very well with the experimental findings. Obtained results on band structure and density of states show that the TbH2.25 (I4/mmm) system is metallic due to a non-vanishing density of states at the Fermi level.

Ab initio calculations have been performed by the linearized augmented plane wave (LAPW) method as implemented in the WIEN2K code within the density functional theory to obtain the structural, electronic and optical properties of ZnSnP2 in the body centered tetragonal (BCT) phase. The six elastic constants (C11, C12, C13, C33, C44 and C66) and mechanical parameters have been presented and compared with the available experimental data. The thermodynamic calculations within the quasi-harmonic approximation is used to give an accurate description of the pressure-temperature dependence of the thermal-expansion coefficient, bulk modulus, specific heat, Debye temperature, entropy Grüneisen parameters. Based on the semi-empirical relation, we have determined the hardness of the material; which attributed to different covalent bonding strengths. Further, ZnSnP2 solar cell devices have been modeled; device physics and performance parameters have analyzed for ZnTe and CdS buffer layers. Simulation results for ZnSnP2 thin layer solar cell show the maximum efficiency (22.9%) with ZnTe as the buffer layer. Most of the investigated parameters are reported for the first time.

This paper explores structural, phonon, electronic and thermoelectric properties of Zr0.25Ti0.75GeSb. By doping 0.25 Zr to TiGeSb the space group of this compound changes to P4/mm. Lattice constants and bulk modulus demonstrate relative increase compared to TiGeSb. This increment is low and expected. Furthermore, phonon calculations of Zr0.25Ti0.75GeSb were carried out by Quantum Espresso code. Electronic and thermoelectric calculations were performed using Wien2k software and accessory code Boltztrap. This compound has metallic nature and contribution of i orbitals among atoms with d orbital for atom “Ti1” is the highest. In thermoelectric properties, figure of merit of Zr0.25Ti0.75GeSb is significantly increased compared to bulk of TiGeSb in both xx and zz directions at low temperatures. However, at high temperatures it is lower.

Structural, electronic and magnetic properties of the hexagonal magnetoelectric YMnO3 oxide in low symmetry were investigated using density functional theory calculations and the full-potential linearized augmented plane wave method implemented in the Wien2k code. The results showed that the internal atomic relaxation calculations are in good agreement with the experimental data. The obtained results from electronic band gap calculations using the Perdew–Burke–Ernzerhof generalized gradient approximation (GGA-PBE) reveal that the YMnO3 has a metallic character. However, the Tran–Blaha-modified Becke–Johnson (TB-mBJ) approach predicts a semiconductor type, as expected for YMnO3. The estimated band gaps are found to be close to 0.45 eV (ferromagnetic, FM) and 0.6 eV (anti-ferromagnetic, AFM). Moreover, calculations yielded a total magnetic moment of about 24 μB per unit cell. The magnetic moment carried by Mn atoms is revealed to be sensitive to the used approximation. Its value is equal to 3.3 μB and 3.5 μB for the GGA and GGA+mBJ approaches, respectively. Both values are in accordance with the experimental data.

The solar cells and thermoelectric generators are the main sources of renewable energy. In current article, we have analyzed the electronic, optical, and transport characteristics of K2TiI6 and Rb2TiI6 by density functional theory (DFT) based Wien2k code through modified Becke and Johnson (mBJ) potential. The structural and thermodynamic stability are certified by tolerance factor (0.99–1.0) and negative formation energy. The bonding nature is illustrated by color charge density. The band gap of 1.39 eV and 1.48 eV for K2TiI6 and Rb2TiI6 demonstrate the maximum absorption of light takes place in visible region (1.5 eV–3 eV), which makes them new potential materials for solar cells. Moreover, the reflection of light and optical loss is negligible in the visible region. The transport characteristics have been explained by classical Boltzman transport (CBT) based BoltzTraP code in terms of thermal to electrical conductivity ratio, Seebeck coefficient, and figure of merit. The figure of merit lies between 0.75 to 0.76, which is decent for thermoelectric characteristics.

The spinel oxides SnV2O4 and SnCr2O4 are analysed to reveal the mechanical, electronic and magnetic properties using Wien2k software. The negative formation energy and positive elastic constants sh...

By using WIEN2k code, we investigated the mechanical and thermoelectric properties of magnesium based MgX2O4 (X = Rh and Bi) spinels. To compute the mechanical behavior of MgX2O4 (X = Rh and Bi), the Perdew-Bruke-Ernzerhof (PBEsol) flavor of generalized gradient approximation is used. From structural optimization, ground state lattice constant ( a 0 ) show a comparable with the previously evaluated theoretical and experimental values. The Born stability criterion represents that the investigated spinels are stable in the cubic phase and their ductile behaviors are observed by calculating Pugh’s ratio as well as Poisson ratio. Besides, thermodynamic behavior is concluded in terms of the Debye temperature. To investigate the electronic and thermoelectric behavior, the modified Becke and Johnson (mBJ) potential is employed. Finally, we investigated the thermoelectric behavior to represent the importance of studied spinels in thermoelectric appliances by calculating the figure of merit (ZT). High values of the See-beck coefficient and ZT at room temperature explores the potential of the studied spinels in thermoelectric devices.

Density functional theory calculations as employed in Wien2K code are used to investigate the structural, thermodynamic, and optoelectronic behavior of BeTiO3 perovskite at various pressures. The tolerance factor within the range of 0.93–1.04 suggests that the studied perovskite is thermodynamically stable in the cubic phase along with structural and mechanical properties. By inducing the pressure, the dependent specific heat capacity and the electron density are explored from 0 to 1000 K. At 132 GPA, the band gap becomes direct in nature (indirect band gap at 0 GPA), where the optical transitions take place.

The first-principles calculations of Co(Mo,Tc)MnSb compounds were performed by using Wien2k with Generalized Gradient Approximation (GGA) and Tran Blaha modified Becke Johnson (TB_mBJ) methods. All compounds were obtained as ferromagnetic (FM) materials according to volume-energy optimization curves. In GGA method, both compounds have metallic ferromagnet nature while these were in TB_mBJ method nearly half-metallic ferromagnet characters. In spin-down band structures, both compounds had indirect band gaps in both methods used. The total magnetic moment values were completely compatible with the Slater-Pauling (SP) rule and these values were obtained as 3.00 and 4.00 μ B /f.u. for Co(Mo,Tc)MnSb compounds, respectively. According to elastic calculations, Co(Mo,Tc)MnSb compounds are elastically stable and ductile materials . The Debye temperatures of Co(Mo,Tc)MnSb compounds were obtained above the room temperature as 408.040 K and 444.079 K, respectively.

The transition-metal dichalcogenides (TMDC) attracted a lot of attention for a variety of applications and more particularly as positive electrodes in lithium batteries. Among these materials the most intensively studied, we find semiconductors such as tungsten diselenide WSe2. In this work, we have perform first-principle calculations to investigate the structural and electronic properties of WSe2 compound, using the density functional theory DFT within the full-potential linearized augmented plane wave method (FP-LAPW) implemented in the code WIEN2k. The Generalized Gradient Approximation (GGA) as proposed by Perdew et al. was used to describe the exchange–correlation potential; and so to obtain the structural properties to assess the equilibrium lattice, the total energy of the system for different values of the primitive mesh and determining the volume at equilibrium, the compressibility modulus and the energy of the ground state, which are close to experimental results reported in the literature. The electronic properties were obtained by calculating the band structure and the density of state ″DOS″, by using three approaches: Local Density Approximation (LDA), Generalized Gradient Approximation (GGA) and modified Becke-Johnson (mBJ). The calculated energy bands indicate the semiconductor behavior of WSe2 with an indirect band gap of 0.9 eV using LDA, of 1 eV with GGA and 1.18 eV by mBJ. This last band gap value is the closest of the experimental result of 1.2 eV.

The zinc antimonide ZnSb is one of the most materials which have been studied intensively in recent years, due to its importance in thermoelectric applications, and as well as its use as an electrode in rechargeable Li-ion batteries. For this reason, we were interested in studying its structural and electronic properties. These properties have been calculated using the density functional theory DFT within the full potential linearized augmented plane wave (FP-LAPW) method used with WIEN2k code. The Generalized Gradient Approximation and the Local Density Approximations were used to model the exchange–correlation potential which was applied to determine the structural properties as well as the total energy (E0), the bulk modulus (B) and its first pressure derivative (B’), at a minimum equilibrium volume (V0). We also used the Tran-Blaha modified Beck Johnson (TB-mBJ) method to determine the total and partial density of states TDOS and PDOS respectively, which depicted that the electrons of Sb-5p orbital have a dominant contribution at the top of the valence band near the Fermi level, and show the sharp peaks in the conduction band. The electronic band structure shows clearly semiconductor behavior, with an indirect gap of 0.59 eV. This last result is in good agreement with an experimental result of 0.61 eV.

The structural and optoelectronic properties of AlxGa1−xN (x = 0, 0.125, 0.375, 0.625, 0.875, and 1) semiconductors are studied in detail by applying the full-potential linearized augmented plane-wave method in density functional theory in WIEN2k software. The lattice parameter, the bulk modulus, and its pressure derivative are calculated using the Perdew–Burke–Ernzerhof generalized gradient approximation and by fitting the calculated total energy to the Murnaghan equation. These parameters are found to be in excellent agreement with experimental and theoretical results for both the GaN and AlN compounds. For the Al0.125Ga0.875N, Al0.375Ga0.625N, Al0.625Ga0.375N, and Al0.875Ga0.125N alloys, because of the lack of the theoretical and experimental data, our results can be considered as first predictions. The Tran–Blaha modified Becke–Johnson approach (TB-mBJ) is applied to determine the optoelectronic properties. The results demonstrate that GaN and the AlxGa1−xN alloys with x = 0.125, 0.375, 0.625, and 0.875 have a direct Γ–Γ bandgap, whereas the binary AlN compound has an indirect Γ–X bandgap. Furthermore, the optical properties, such as the dielectric function, refractive index, reflectivity, absorption coefficient, and energy loss function, are presented and discussed in detail; their wide bandgap means that these compounds can be applied in optoelectronic devices for application in the main parts of the ultraviolet and visible spectrum.

We study hydrogen storage properties of Nb doped ZrNiH3 using the first-principles calculations based on density functional theory (DFT). To achieve such calculations, we used full potential linearized augmented plane waves (FP-LAPW) method implanted in WIEN2K code. Total energy and density of states (DOS) are computed for Zr1-xNbxNiH3 (x = 0 and 0.1). It turns out that substituting 10% of zirconium by niobium in ZrNiH3 matrix involves a destabilization of the system. This destabilization is induced by the formation of a new hybridization between niobium and hydrogen atoms. Furthermore, the thermodynamic stability in terms of its energy of formation, as well as the capacity of the material to store hydrogen are discussed. Noteworthy that from FP-LAPW we report that Nb doped ZrNiH3 lower the desorption temperature to 305.77 K without significant reduction of the hydrogen storage capacity. This lowering of the temperature desorption makes the material very useful for hydrogen storage in solids.

A set of ZnMoO4 polycrystalline samples was synthesized by solid state reaction method and characterized by XRD structural analysis, ICP elemental analysis, SEM-EDX analysis, UV–Vis diffuse reflectance spectroscopy. The photoluminescence (PL) properties of ZnMoO4 samples were studied in 8–300 K temperature range with use of synchrotron radiation as an excitation source. The geometry-optimized electronic structure calculations of perfect and defective ZnMoO4 crystals were carried out by the DFT-based band-structure methods, plane-wave pseudo-potential (CASTEP program package) and FP-LAPW (Wien2k package). A number of point defects which can influence the luminescence properties of ZnMoO4 was considered in calculations, namely the oxygen vacancy Vo, compensated vacancies Vo + VZn, tungsten impurity WMo and the MoO3-deficient phase Zn3Mo2O9. Comparative analysis of experimental data and calculation results allowed explanation of the origin of the red and blue-green luminescence emission bands of ZnMoO4 as well as formation of their excitation spectra. It is assumed that the green component of ZnMoO4 luminescence emission, like in other molybdates of MIIMoO4 family (MII = Ca, Sr, Cd, Pb) originates from radiative annihilation of excitons self-trapped on regular MoO4 groups. The Red component of ZnMoO4 emission has a defect-related origin and it originates from radiative transitions in MoO4 groups located near oxygen vacancies.

Using the full-potential linearized augmented plane wave method (FP-LAPW) based on the density functional theory (DFT) as implemented in the Wien2k package, first principles calculations were performed to investigate structural, electronic, magnetic, optical and for the first time thermoelectric properties of Sr2CrTaO6 double perovskite compound. The exchange correlation potential is treated by the generalized gradient approximation (GGA) and GGA + U where U is on-site Coulomb interaction correction. The trans-blaha-modified Becke–Johnson (TB-mBJ-GGA) is also used. Obtained results for the structural, electronic, and magnetic properties are in good agreement with the available experimental data. Structural and electronic properties show that our compound shows half-metallic ferrimagnetic phase ground state. Optical properties such dielectric function, absorption coefficient and reflectivity were computed and confirm that our compound is very suitable for device applications in the major parts of the spectrum (infrared, visible and ultraviolet). The novelty of our work is the study of thermoelectric properties of Sr2CrTaO6 double perovskite such as electrical conductivity, Seebeck coefficient and factor of merit.

The objective of this paper is the examination of structural, electronic, and optical properties of binary AlSb, AlN, and their novel ternary AlNxSb1−x alloys (x = 0.25, 0.5, and 0.75), within the full-potential linearized augmented plane wave method based on the density functional theory as implemented in the WIEN2K code. The computed negative formation energies of AlNxSb1−x alloys prove that these compounds are thermodynamically stable. The structural parameters are calculated using the generalized gradient approximation GGA–PBEsol, such as the lattice parameters, bulk modulus, and pressure derivatives, which are in good accordance with both theoretical and experimental data for binary compounds. However, for the ternary alloys, our results are considered as a first prediction. The lattice constants and the bulk modulus are compared with Vegard’s law and the linear concentration dependence. The Tran–Blaha-modified Becke–Johnson approach “TB–mBJ” is employed to determine the electronic and optical properties; the results demonstrate that the binary compounds have indirect band gaps (Γ–X), whereas the ternary AlNxSb1−x alloys exhibit direct band gaps (Γ–Γ) semiconductors, with values of 0.472, 0.915, and 1.962 eV for AlN0.25Sb0.75, AlN0.5Sb0.5, and AlN0.75Sb0.25, respectively. The obtained results are reported, discussed, and compared with previous and the experimental data.

The structural behavior of MgIn2X4 (X = S, Se) has been elaborated by FP-LAPW + lo method as included in the Wien2k code. The stability of the phase has been confirmed by negative formation energy (−1.24 eV for MgIn2S4 and -0.78 eV for MgIn2Se4). The band gap dependent opto-electronic and thermoelectric properties are realized by modified Becke-Johnson exchange potential. The electronic band gap tuned from ultraviolet to visible (3.1 eV and 1.9 eV) by replacing the S with Se that motivated the studied spinels for photovoltaic and solar applications. Moreover, the attenuation of light, dispersion, transparency, reflection and energy loss when light scattered from material are discussed as function of energy. The thermal conductivity to electrical conductivity ratio, potential gradient and thermal efficiency in the range 0.78–0.80 are elaborated. The comparative study of opto-electronic and thermoelectric properties for energy harvesting increases the potential for optoelectronic than thermoelectric applications.

In this study, we employed the density functional theory (DFT) approach using WIEN2k code to study the magnetic and optical behaviors of PbCrO 3 and PbFeO 3 perovskites in both cubic and tetragonal phases. We determined the stability of the ferromagnetic state in terms of the enthalpy of formation, the half-metallic behavior, and spin polarization. The origin and nature of the ferromagnetic state were attributed to John–Teller distortion and a super-exchange mechanism. Comparisons of the calculated crystal field, John–Teller distortion, and exchange energies indicated the stability of the ferromagnetic nature. Due to strong hybridization, the magnetic moment was reduced at the Cr/Fe sites but generated at the nonmagnetic sites. The optical characteristics were explained by in-depth analyses of the polarization, plasmonic resonance, transparency, and other features in terms of the computed parameters.

We have investigated the electronic and optical properties of β-MnS with III-type antiferromagnetic ordering using full potential linearized augmented plane wave (FP-LAPW) method within the framework of the spin-polarized density functional theory as implemented in WIEN2k package. Firstly, it is proven that III-type antiferromagnetic ordering is stable in comparison with others from the total energy calculated using the Perdew-Burke-Ernzerhof (PBE) functional. Then, we study the electronic properties of β-MnS for an energy range from −5 eV to 5 eV using mBJ exchange and PBE semilocal correlation, our calculations show an indirect energy band gap of 2.275 eV and the strong hybridization of Mn-3d states and S-3p state in valence band. Additionally, we also investigate the effect of spin-orbit coupling on the electronic properties, this causes a very slight red-shift in both Mn-3d and S-3p states but no change of energy gap is observed. Finally, the linear optical properties such as absortion coefficient, reflectivity, energy loss function, refractive index, extinction coefficient and optical conductivity have been derived from calculated complex dielectric function for energy from 0 eV to 24 eV considering all the three polarization directions (E//x, E//y and E//z). The obtained results indicate that β-MnS is an optically isotropic material when the energy is small and it becomes anisotropic for high energy.

In the present research paper, the structural, electronic and thermodynamic properties of the Si1-yCy binary in a super cell consists of 08, 16 and 32 atoms were studied. The Full Potential-Linearized Augmented Plane Wave (FP-LAPW) method was used within the Density Functional Theory (DFT); which was performed directly in WIEN2K code.. The exchange and correlation potential is treated with the local density approximation (LDA). The deviation of lattice parameter was analyzed by the use of Vegard’s Law depending on the concentration and, therefore, the results seem to obey the Vegard’s law. Moreover, the modified exchange potential proposed by Becke -Johnson to calculate the gap were applied. The results achieved by the local density approximation (LDA) and potential of modified Becke -Johnson (MBJ-LDA) was discussed. Difference in the gap was observed especially in low concentrations y = 0.125; the gap value increases from −0.016 eV to 0.177 eV and when y = 0.5 the gap improved from 1.302 eV to 2.272 eV obtained by the LDA and the MBJ respectively; close to the experimental value 2.39 eV. Next, in order to study the microscopic origin of the bowing gap, Zunger’s approach was introduced. Finally, thermodynamic properties were calculated as well as the results were discussed. Based on the results, it can be concluded that the values obtained are in a better agreement with those of other theoretical and experimental data.

In this work, the structural, electronic and optical properties of pure and aluminum (Al) doped gallium phosphide (GaP) in zinc-blende (ZB) phase are elaborated using full potential linearized augmented plane wave (FP-LAPW) method as implemented in Wien2K code. The calculated lattice parameters show decreasing behavior with increasing the concentration of Al contents. Band gaps of AlxGa1−xP are investigated by generalized gradient approximation (GGA) and found to be the increasing linear behavior by increasing the concentration of Al. Furthermore, the optical properties including dielectric constants, refractive index, reflection coefficient, absorption coefficient and extinction coefficient of AlxGa1−xP at different compositions are also calculated and discussed. In order to check the mechanical behavior under the influence of applied pressure the elastic coefficients of all these composition have been calculated and discussed. Calculated parameters i.e. lattice constants, band gaps, and optical variables are very close to the experimental values which suggested that the materials are good candidates for the opto-electronic devices. Further, the elastic constants for all compounds which describes the mechanical behavior are reported for the first time and there is no data available for comparison.

Motivated by the lack of information on several physical properties of KUO3, we have undertaken a complementary and comparative study to the work already achieved on this compound. Magnetic ground state and the effect of hydrostatic pressure on elasticity, electronic and magnetic properties of KUO3 were studied using FP-(L)APW + lo method. The most stable magnetic phase of KUO3 has been found to be G-Type antiferromagnetic order, consistent with the experimental results. The study of the elasticity has shown that KUO3 maintains its mechanical stability under any hydrostatic pressure less than 41.9 GPa. Young's modulus anisotropy has been studied and according to 2D and 3D representations of its dependence along the different crystallographic directions, we have found that it is largely anisotropic. The effective on-site Coulomb interaction parameter "Ueff" was estimated by constrained-LDA method “cLDA” to treat the strong correlation of Uranium 5f-electrons. Based on Ueff value estimated by cLDA, GLLB-SC and mBJ potentials were used to predict the band-gap of KUO3 from which it was found to be indirect with X-Γ type and its value is very close to that of direct with Γ-Γ type. The quantum theory of atoms in molecules (QTAIM) was used for a detailed analysis of chemical bonding nature between the different atoms forming KUO3 from where we have found that the ionic character is predominant. This study also made it possible to determine the partitioning of the bulk modulus into atomic basins contributions, from which it has been found that its total value is very close to that found in structural part.

Electronic structure of AgAlO2 have been investigated using first principles calculations based on the full-potential linearized plane-wave method as implemented in WIEN2k package. Generalized gradient approximation (PBESol) and Tran-Blaha modified Becke-Johnson exchange potential (mBJ) are adopted for the treatment of exchange-correlation effects. Calculated electronic properties show the considerable improvement of results with mBJ potential while the strong hybridization between O-2p and Ag-4d states is revealed. From the band structure obtained with mBJ potential, the thermoelectric properties are calculated using semi-classical Boltzmann transport theory. Obtained results suggest that AgAlO2 is a good thermoelectric p-type compound with figure of merit value close to unity at charge-carrier concentration about 1017 (cm−3). Finally, the thermodynamic properties including bulk modulus, isochoric and isobaric heat capacities, thermal expansion and Debye temperature of AgAlO2 also are calculated using quasi-harmonic Debye model and the obtained results are discussed in detail.

By using first-principles calculations we studied the electronic, optical and magnetic properties of ZnO co-doped with Eu and Pm. In this calculation, we used Wien2k code based on full potential linearized augmented plane waves (FP-LAPW) method with the modified Becke-Johnson (mBJ) approximation. This correction gives good band gap compared to experimental band gap. The introduction of Eu and Pm codoping leads to an increase in the band gap. Electrons can transit easily from the valence band to the conduction band, which results in an enhancement of visible light absorption in a wider absorption range. Absorption spectra reach a high value in visible and infrared light regions. With the significance of the obtained results, the studied compounds may potentially find spintronic and optoelectronic applications.

Density functional theory (DFT) calculations using full potential linearized augmented plane wave (FP-LAPW) method as implemented in the Wien2k code have been performed to investigate the structural, electronic and optical properties of copper iodide (γ- CuI) in zinc blende phase. Optical properties have been studied theoretically and various optical constants such as complex dielectric constant, refractive index, reflectance, transmittance, absorption co-efficient, optical conductivity and electron energy loss are discussed with respect to the photon energy. We have also discussed the progresses of the overall results of Tran–Blaha modified Becke–Johnson (TB-mBJ) potential and have been compared to the standard generalized gradient approximation (GGA) method. Exciton binding energy is also calculated and the value is found to be 60 meV. As the absorption coefficient is maximum in the ultra-violet (UV) region for CuI, it is a very good material active in UV region and hence it can be used in optoelectronic device applications.

We have performed first-principles calculations on orthorhombic antimony sulphide (Sb2S3) nanowire using full-potential linearized augmented plane wave (FP-LAPW) method based on the density-functional theory (DFT) as implemented in WIEN2k package to investigate the electronic and optical properties. Engel–Vosko generalized gradient approximation (EV-GGA) is used as exchange-correlation functional. The nanowire is simulated in the [001] direction with vacuum in two directions using supercell method. The results are compared with Sb2S3 bulk results obtained in our pervious study. We have found that the electronic and optical properties significantly change in Sb2S3 nanowire. The density of state (DOS) for Sb2S3 nanowire calculated is higher than bulk Sb2S3 and from the electronic band structure, the indirect band gap is about 0.12 eV where this value is much lower than Sb2S3 bulk. However, this value is much lower than experimental value. The optical properties including absorption coefficient, reflectivity, refractive index and energy loss function are derived from the calculated complex dielectric for photon energy up to 20 eV to understand the optical behavior of Sb2S3 in one-dimensional (1-D) nanostructure. From analysis, the optical response of Sb2S3 nanowire demonstrate quite interesting optical behavior for one-dimension (1-D) nanostructure. The absorption coefficient for Sb2S3 nanowire is considerably higher in visible light range than Sb2S3 bulk.

In present study, thermo-elastic and vibrational properties of XMgGa (X = Li, Na) half Heusler compounds are investigated using density functional theory implemented in WIEN2k and Quantum ESPRESSO codes. Generalized gradient approximation as an exchange correlation functional is used in Kohn-Sham equations to find three elastic constants C11, C12 and C44 for C1b type structures. First, we optimized the structures of these Heusler compounds. These three elastic constants are then used to determine different elastic modulii like bulk modulus, shear modulus, Young modulus and other mechanical parameters like Pugh's ratio, Poisson's ratio, anisotropic ratio, sound velocities, Debye temperature and melting temperature. On behalf of these mechanical parameters, the brittle/ductile nature and isotropic/anisotropic behavior of the materials are investigated. Different regions of vibrational modes in the materials are also discussed on behalf of Debye temperature calculations. The vibrational properties of the half Heusler compounds are computed using Martins-Troullier pseudo potentials implemented in Quantum ESPRESSO. The phonon dispersion curves and phonon density of states in first Brillion zone are obtained and discussed. Reststrahlen band of LiMgGa is found greater than NaMgGa.

We propose a hybrid approach which employs the dynamical mean-field theory (DMFT) self-energy for the correlated, typically rather localized orbitals and a conventional density functional theory (DFT) exchange-correlation potential for the less correlated, less localized orbitals. We implement this self-energy (plus charge density) self-consistent DFT+DMFT scheme in a basis of maximally localized Wannier orbitals using Wien2K, wien2wannier, and the DMFT impurity solver w2dynamics. As a testbed material we apply the method to SrVO$_3$ and report a significant improvement as compared to previous $d$+$p$ calculations. In particular the position of the oxygen $p$ bands is reproduced correctly, which has been a persistent hassle with unwelcome consequences for the $d$-$p$ hybridization and correlation strength. Taking the (linearized) DMFT self-energy also in the Kohn-Sham equation renders the so-called "double-counting" problem obsolete., Comment: 2nd version as submitted, taking into account the k-dependence of the double counting on the DMFT side. 10 pages, 4 figures

First-principles calculations, based on the density functional theory (DFT), have been used to predict the structural, elastic, electronic and magnetic properties of XMg3O4 (X = Li, Na, K and Rb) compounds. They have been performed by employing the full-potential linearized augmented plane wave method (FP-LAPW), as implemented in Wien2k code. It was found that all compounds were ferromagnetic by energy minimization procedure. The computations of elastic constants show that our compounds are mechanically stable. The electronic properties, through the density of states and band structures, indicate that these compounds exhibit half-metallic nature, and the spin up band gaps (HMgaps) were found to be5.32 (0.18) eV, 4.49 (0.28) eV, 3.01 (0.38) eV and 1.53 (0.17) eV for LiMg3O4, NaMg3O4, KMg3O4 and RbMg3O4, respectively. In addition, for all compounds, the calculated integer magnetic moment value of 1.0 µB fulfills the necessary condition of the half-metallicity. The calculated Curie temperatures $${T}_{c}$$ are 537, 365, 260 and 113 K for LiMg3O4, NaMg3O4, KMg3O4 and RbMg3O4, respectively.

In this study, we present our predicted results related to the structural, electronic, and optical properties of Ga(x)In(1-x)AsyN(1-y) quaternary alloys while assessing the associated zinc blende binary and ternary compounds. All calculations are performed by employing the full-potential linearized augmented plane wave plus local orbital method (FP-L(APW + lo)) based on density functional theory (DFT) and implemented in the WIEN2k computational package for crystalline materials. The exchange-correlation energy and potential functional are treated by the local density approximation (LDA) parameterized by Perdew-Wang (PW) and the PBE functional for solids, i.e., PBEsol-GGA, for the calculations of structural parameters, while the Tran-Blaha Becke-Johnson (TB-mBJ) potential approximation combined with PBE-GGA is applied for band structure calculation. The composition-dependent results of the lattice parameters, bulk modulus, and bandgap energy are also studied by performing a quadratic fit, where nonlinear variations in the results are observed. One can note that the bandgap energies are direct for all considered compositions (x, y). Moreover, the dielectric behavior, refractive index, and loss energy are predicted in the context of the optical properties, and the variation in the composition slightly affects the optical stability of the studied alloys. We have also carried out predictions of the thermodynamic properties such as the lattice parameter a(P, T), the Debye temperature theta(D), the heat capacity C-v, and the entropy S using the GIBBS program. To the best of our knowledge, this work represents the first theoretical study on these quaternary alloys and awaits experimental confirmation.

The recently observed ferroelectricity in thin films of pure and doped Hafnium oxide (HfO2) has initiated a sustaining effort to stabilize its ferroelectric phase which is the polar orthorhombic (o) phase with space group Pca21. This polar o-phase of the oxide does not appear in its phase transition sequence and is also not thought to be stabilized in bulk oxide. Here, we report the stabilization of three o-phases of this oxide in bulk with space groups Pbca, Pca21 and Pbcm in presence of Yttrium (Y) dopant. For inducing o-phase, 10 at% of Y-dopant has been used and temperature mediated phase transformation from monoclinic (m) to o-phase has been observed. The third o-phase with space group Pbcm could be stabilized for the first time in bulk oxide by Y-dopant. All the o-phases in presence of m-phase could be identified by Time Differential Perturbed γ-γ Angular Correlation (TDPAC) Spectroscopy. The TDPAC parameters assigned to Pbcm phase confirm the theoretical modelization for the phase performed by Wien2K calculation based on Density Functional Theory (DFT). The present work reports the possibility of stabilizing different o-phases including polar one and shows the widening of scope of this oxide for future ferroelectric applications.

Semiconductor perovskite material has given important interest as a potential thermoelectric material (TE) due to its large thermopower (Seebeck coefficient, S). VScO3 Semiconductor Perovskite is investigated by the Density Functional Theory (DFT) using full potential linearized augmented plane wave (FP-LAPW) method with mBJ approximation. The energy band structure obtained from WIEN2k calculations is used to calculate the transport coefficients via the semi-classical Boltzmann transport theory with constant relaxation time (τ) as employed in the BoltzTraP package. VScO3 semiconductor perovskite is considered as a potential candidate for thermoelectric application. The calculated elastic constants show that VScO3 perovskite suitably verify Born's mechanical stability criteria and characterized by ductile manner.

In this paper, we reported a computational study of the 2-D nanomaterial (SnSi) as a possible new nanomaterial to be synthesized. This study is chiefly based on density functional theory calculation, which is implemented in the wien2k code. In fact, we calculated the electronic properties such as electronic band structures, band gaps, DOS, formation energy, and electrical conductivity of three types of monolayers Stana-Silicene; (SnSi, SnSi3, and SnSi7) with various concentrations (50%, 25%, and 12.5%) of the Sn and the Tin atoms. By computing the formation energy of these materials within various concentrations of the Sn atoms, we observed that the SnSi monolayer has more stability than SnSi3 and SnSi7. Another important result is that the electrical conductivity of SnSi depends on the concentrations of the Sn atoms. Indeed, it increases by increasing the concentration of the Sn atoms. By using various concentrations of the Tin atoms, we found out that all these nanomaterials behave as a semiconductor material within direct electronic band gaps.

The present work investigates the less explored thermoelectric properties of the n-type GaN semiconductor by combining both experimental and computational tools. The Seebeck coefficients of GaN epitaxial thin films were experimentally measured in the wide temperature range from 77 K to 650 K in steps of ∼10 K covering both low and high-temperature regimes as a function of the carrier concentration (2 × 1016, 2 × 1017, 4 × 1017 and 8 × 1017 cm-3). The measured Seebeck coefficient at room temperature was found to be highest (-374 μV K-1) at the lowest concentration of 4 × 1016 cm-3, and decreases in magnitude monotonically (-327.6 μV K-1, -295 μV K-1, -246 μV K-1 for 2 × 1017, 4 × 1017, 8 × 1017 cm-3, respectively) as the sample carrier concentration increases. The Seebeck coefficient remains negative in the entire temperature range under study indicating that electrons are the dominant carriers. To understand the temperature-dependent behaviour, we also carried out the electronic structure and transport coefficient calculations using the Tran-Blaha modified Becke-Johnson (TB-mBJ) potential and semiclassical Boltzmann transport theory implemented in WIEN2k and BoltzTraP code, respectively. The experimentally observed carrier concentrations were used in the calculations. The estimated results obtained under constant relaxation time approximations provide a very good agreement between the theoretical and experimental data of Seebeck coefficients in the temperature range from 260 to 625 K.

WloopPHI is a Python code that expands the features of WIEN2k, a full-potential all-electron density functional theory package, by the characterization of Weyl semimetals. It enables the calculation of the chirality (or "monopole charge") associated with Weyl nodes and nodal lines. The theoretical methodology for the calculation of the chirality is based on an extended Wilson loop method and a Berry phase approach. We validate the code using TaAs, which is a well-characterized Weyl semimetal, both theoretically and experimentally. Afterwards, we applied the method to the characterization of YRh$_6$Ge$_4$ and found two sets of Weyl points (ca. 0.2 eV below the Fermi energy) together with a topological nodal line (protected by mirror symmetry) crossing the Fermi energy and mapped their chiralities., 31 pages, 9 figures

In this paper, we have investigated the structural, elastic, electronic, and thermoelectric properties of chalcopyrite B2BiN using the first-principles calculations via the density functional theory (DFT) implemented in wien2k code. We negative the energy formation founded indicates the stability of these alloys in ambient conditions. The obtained results predict that the studied system shows a brittle and stiff behavior based on the analysis of the elastic constants and their derived parameters such as Young’s modulus (220–240 GPa), Poisson’s ratio (0.163–0.188), and the Debye temperature (503.33 K). Moreover, the compound has an indirect bandgap of 1.37 eV, which is close to the ideal value of 1.40 eV for the solar light absorber. Its merit factor (ZT) varies from 0.96 and 0.92 for temperatures ranging between 300 and 900 K and a high value of the Seebeck coefficient (S) of 2750 μV/K at 300; these two important parameters allow the B2BiN structure to have an improvement in thermoelectric performance and can be a potential candidate for solar panel devices. To the best of our knowledge and according to the researches available in the literature, there are no experimental and theoretical studies on elastic and thermoelectric properties of B2BiN.

Theoretical calculations are performed to investigate the electronic, structural and optical properties of double perovskite oxide A2ZnTeO6 (A = Ca, Sr, Ba). The calculations are based on the Density Functional Theory (DFT) using the WIEN2k code. The exchange–correlation potential is treated with generalized gradient approximation (GGA-PBE). Additionally, the Tran Blaha modified Becke-Johnson exchange potential (TB-mBJ) is employed for electronic and optical calculations due to that it gives very accurate results of band gap in solids. In order to estimate the ground state parameters, total energies are calculated with respect to cell volume. Also, the energies are fitted with Murnaghan equation of state. The estimated ground state parameters are comparable with the available experimental data. The band structure calculations reveal that these compounds exhibit semiconducting behavior with a direct band gap. To explore the optical transitions in these compounds, the real and imaginary parts of the dielectric function are analyzed at ambient conditions and the important optical constants are calculated and discussed.

In the past few years it became regularly possible to measure valence band X-ray photoelectron spectra (XPS) using variable excitation energies. This ranges from UV-light to conventional X-ray sources (like Al Kα) all the way to synchrotron radiation with energies of several keV. In order to explain the observed variations in intensity with respect to the excitation energy, we performed XPS calculations using the WIEN2k code. The new PES module computes the XPS spectra using a combination of partial density of states times excitation-energy-dependent atomic-orbital cross sections. It considers as additional correction the charge fraction of the corresponding orbital located inside the atomic spheres. The resulting XPS spectra are compared with experimental data for SiO2, PbO2, CeVO4, In2O3 and ZnO at different excitation energies and in general good agreement between the simulated and experimental spectra has been achieved. In some cases significant unexpected contributions like Pb-6d in PbO2 or Zn-4p in ZnO appear and explain some features in the experimental spectra which previously have not been identified.

In this work, we report theoretical and experimental studies on the structural, electronic and optical properties of wurtzite Zn1−xCdxO alloys. The theoretical investigations were conducted using the density functional theory (DFT) as implemented in the Wien2k package which is based on the full potential linearized augmented plane wave (FPLAPW). The modified exchange potential proposed by Becke-Johson (mBJ) with local gradient generalized approximation (GGA) was used in this study. The lattice parameters, electronic structure and optical properties were studied in details for the composition x of cadmium 0, 0.16, 0.25, and 0.33. Experimentally, Zn1−xCdxO alloys were grown by the sol–gel spin coating method with different cadmium concentrations specifically x = 0, 0.10, 0.20, and 0.30. The obtained experimental results were systematically analyzed and compared with the DFT calculations. From the theoretical findings, it is noticed that the structural and electronic properties of Zn1−xCdxO are strongly affected by the Cd doping amount. The lattice parameters increase and the band gaps decrease with the x fraction of cadmium showing a quantitative agreement with the experimental results. Moreover, the investigation of the total and partial density of the Zn1−xCdxO alloy for the different bands reveals that the optical transition between O-2p states in the top of valence band and Zn-4s states in the bottom of the conduction band is shifted to lower energy range as the Cd concentration increases. In addition, the dielectric function, the absorption coefficient, and the refractive index and discussed for the different cadmium composition. Combining both theoretical calculations on Zn1−xCdxO alloys with the obtained experimental results provides better understanding of the physical properties dependence on the composition and would help to engineer such alloys for high performance optoelectronic and nonlinear optical devices.

The inverse Heusler alloy Zr2RhAl is investigated using first-principles calculations. The calculations are carried out using the full-potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) method that is employed in the WIEN2k package. The structural, electronic, magnetic, and thermoelectric properties are studied. It is found that the ferromagnetic phase of Zr2RhAl is the most stable with lattice parameter 6.6328 A. The calculations showed that there is an energy gap in the spin down channel whereas the spin up channel is metallic, resulting in a 100% spin polarization at Fermi level. This is an obvious characteristic of half-metallic materials. The calculated total magnetic moment of Zr2RhAl is found to be 2 μB which follows the generalized Slater-Pauling rule. The Curie temperature is estimated to be 607 K using the mean field approximation. Transport properties are studied using the Boltzmann theory with constant relaxation time approximation. The variation of transport properties with temperature is investigated using the two current model.

Recently, we have computed the structural and electronic properties of $$VSb_{2}$$ using the first-principles calculations based on the full potential linearized augmented plane wave (FP-LAPW) method implemented in WIEN2k code. These studies have shown that this material has a metallic character. In this work, we are interested in the study of thermoelectric properties of $$VSb_{2}$$ material using the semi-classical Boltzmann transport theory. The Generalized Gradient Approximation (GGA) is used in the scheme of Perdew–Burke–Ernzerhof (PBE) to treat the exchange correlation effect. Thus, we discuss in detail the temperature effect on the thermoelectric properties such as: the Seebeck coefficient, the thermal conductivity, the electrical conductivity, the electronic specific heat, the figure of merit, the power factor and the Pauli magnetic susceptibility.

Theoretical calculations of Al0·75Co0·25Sb diluted magnetic semiconductor (DMS) were investigated by using both GGA and TB_mBJ methods. First, the energy-volume optimization curves of AlAs and Al0·75Co0·25Sb compounds were plotted and the ferromagnetic (FM) phases were observed to be more energetically stable. The spin-up states showed metallic properties while the spin-down states had a semiconductor nature. While these properties did not change, some differences were observed in the band gap values. Fermi energies were calculated as 0.298 and 0.462 R y and band gap values were obtained as 0.229 and 0.855 eV by using GGA and TB_mBJ methods, respectively. The values of the total magnetic moments did not change and they were obtained as 2.00 μB/f.u. in both methods. Finally, the elastic properties of Al0·75Co0·25Sb compound were calculated. According to these results, Al0·75Co0·25Sb compound is a brittle half-metal ferromagnetic material and it is suitable for use in spintronic applications.

We report variation of the structural, electronic and optical properties of $$\hbox {CsYbF}_{3}$$ perovskite compound in the 0–15 GPa pressure range, using density functional theory, implemented in the Wien2k code. With the increase in pressure, $$\hbox {CsYbF}_{3}$$ crystal squeezes while its cubical symmetry remains unbroken. The calculated electronic properties reveal that $$\hbox {CsYbF}_{3}$$ has a narrow direct band gap of 0.98 eV. The band gap, however, decreases with increase in pressure, and at 15 GPa, $$\hbox {CsYbF}_{3}$$ shows metallic behavior. This reveals the high sensitivity of $$\hbox {CsYbF}_{3}$$ to pressure increase. Furthermore, the calculated pressure-dependent optical properties of $$\hbox {CsYbF}_{3}$$ would find interesting place in optoelectronic devices.

Using the WIEN2k code, we perform ab-initio calculations of the electronic structure and the permittivity tensor of bcc Fe with magnetization along the [001] and [011] directions. The electronic structure is calculated with various numbers of k -points in the full Brillouin zone and the convergence of the calculated data is being studied. Two exchange-correlation potentials are employed, namely LDA and GGA, and their effect on the outcoming spectra is shown. The permittivity tensor is obtained from the electronic structure by the Kubo formula. From the permittivity tensor the complex spectra of linear ( K ) and quadratic ( G s , 2 G 44 ) magneto-optical parameters are extracted. The spectra are compared to the literature.

Current study is a computational work focused on optical properties of Fe doped CdS system. In this regard, Cd atoms are substituted with Fe atoms at second, third and fourth Cd atom site by fixing 1 × 2 × 2 supercell size for each case. Optical properties demonstrate different results due to bonding of Fe with S atoms for three substitutional cases. The study has been performed by employing density functional theory using PBE-GGA approach within Wien2K code. TDOS and PDOS represent hybridization of Fe-3d and S-3p orbitals. Doping at second site shows tremendous change in optical properties and absorption is red shifted while for third and fourth Cd site substitution with Fe atoms exhibits blue shift. Third and fourth Cd site substitution with Fe atom shows almost similar trend in low energy region but becomes significantly distinct at higher energies which enhances optical properties in visible region. Hence, Fe doped CdS system exhibits enhancement of opto-electrical properties which emphasizes its uses in recent optoelectronic devices.

The ground state structural, electronic and optical properties of B1-XInXP (X = 0.0, 0.25, 0.5, 0.75, 1.0) phases have been scrutinized with zinc-blend structure. The full potential linear augmented plane wave method is applied in the framework of density functional theory employing wien2k package. The electronic structure calculations are treated with superior modified-Becke-Johnson potential along with Perdew-Burke-Ernzerhof generalized gradient approximation scheme to harvest the precise energy band gaps in order to get close to experimental outcomes. The computations on ground state structural properties such as volume optimization, equilibrium lattice constants, total equilibrium energy, bulk modulus, compressibility and electronic properties density of states, band structure, energy band gap and in optical properties such as dielectric constant, absorption coefficient, refractive index, electron energy loss function, sum rule, optical reflectivity have been established. The calculated structural, electronic and optical parameters are in excellent agreement with (if) previously reported theoretical and experimental work. The comparative study entailed that mBJ-approach is in strong recommendation for the band gap treatment of materials as it investigates the most close comparable outcomes with the experimental results.