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Using first-principles calculations, we predicted different structures of lithium (Li) atoms with solid electrolytes (e.g., ethylene carbonate (EC)) and their coordination number (n = 3) for the first time. Additionally, we explored the unique properties of the EC absorption of the Li atom using both the equilibrium EC solvent and complex cluster of Li+. Vibrational spectral analysis confirmed that only one type of Li coordinates with EC molecules. The coordination number of EC molecules increases with decreasing minimization or optimization energy and the charge of Li ions. Due to electron affinity and ion charges, only the optimized energy investigation supports the coordination of the EC solvent, which can be calculated by Li+Bn n = 1–3, where B is the organic solvent (ethylene).

The structural, phase stability, elastic and electronic properties of Sb-doped BBi have been systematically investigated in the zinc blende phase by means of the first-principle approach based on the density functional theory (DFT). The structural and elastic properties were computed by using the generalized gradient approximation proposed by Wu and Cohen (WC-GGA). Specifically, the calculated basic structural parameters, such as the lattice constant and bulk modulus, are in good agreement with the existing experimental measurements and theoretical calculations. The phase stability of BBi1-xSbx alloys in the zinc blende and rock salt phases has been investigated with the determination of the transition pressures (Pt) from the zinc blende (B3) to the rock salt (B1) phase. The electronic band structures were determined using the Tran–Blaha-modified Johnson functional. Furthermore, we investigated the mechanical properties and anisotropic behavior of the BBi1-xSbx alloys.

We have studied the doping concentration dependence of the thermoelectric (TE) properties for the n- and p-doped CaIn2P2 layered Zintl phase at two fixed temperatures: T = 600 and 900 K through fir...

In this paper, we have studied the impact of the pressure on the magnetic, elastic, and mechanical properties of the cobalt Co and cobalt hydride CoH using the full-potential linearized augmented plane wave (FPLAPW) method within the generalized gradient approximation (GGA). The obtained results show an excellent agreement with the available experimental and theoretical data at zero pressure, whereas for pressures up to 20 GPa, the results obtained are considered the first quantitative theoretical prediction for cobalt and cobalt hydride. The calculated electronic properties and spin magnetic moment proved that the metallic and ferromagnetic aspects are preserved for both Co and CoH under different pressure values. Moreover, the results achieved for the elastic constants Cij and the mechanical properties (bulk modulus B, shear modulus G, Young’s modulus Y, and Poisson’s ratio ν) verified that studied systems are mechanically stable under the tested pressure range. Besides, the discussed results reveal the enhancement in the ductility for both Co and CoH with increasing pressure.

In this work, we present our predictions on lithium niobate LiNbO3 concerning its structural, electronics, thermal and optical properties. These predictions are done by means of first-principles ca...

We performed ab initio calculations to study the structural and optoelectronic properties of simple and slab phase TaNO using density functional theory (DFT), in which the full potential augmented plane wave (FP-LAPW) method was implemented using the computational code Wien 2k. The modified Becke-Johnson potential (mBJ-GGA) was used for these calculations. The calculated band structure and electronic properties revealed an indirect bandgap for simple TaNO (3.2 eV) and a direct bandgap for slab TaNO (1.5 eV). The interband electronic transitions were investigated from the band structure, and transition peaks were observed from the imaginary part of the dielectric function. These transitions are due to Ta-p, N-p and O-p orbitals for simple TaNO and Ta-p, N-s as well as O-p orbitals for slab TaNO. The plasmon energy was related to the main peak of the energy loss function, which was approximately 10 eV. The static value of the dielectric constant and the refraction were close to the experimental values. In general, slab TaNO shows different properties and is more suitable for optoelectronic applications due to direct bandgap.

A theoretical study of the structural, elastic, electronic, optical, magnetic, and thermoelectric properties of the newly synthetized diamond-like quaternary semiconductor CuMn2InSe4 was carried out in this paper. The calculated equilibrium structural parameters are in excellent agreement with available experimental data. The single-crystal and polycrystalline elastic moduli were predicted using energy strain technique. Electronic properties, including band energy dispersion, total and projected densities of states, and charge distribution map, were calculated and analyzed. Total and local magnetic moments were determined. Linear optical functions were predicted from the calculated band structure. We studied the chemical potential dependence of the thermoelectric parameters, including Seebeck coefficient, electrical conductivity, thermal conductivity, and power factor. The maximum power factor and the corresponding chemical potential are estimated. The obtained results were compared with available ones.

The zone-center phonon frequencies and the elastic properties of six ternary chalcopyrite compounds represented by ABSe2 (A = Cu and Ag; B = Al, Ga and In) are systematically calculated by using the rigid ion model. In the present paper, we calculate four bond-stretching and three bond-bending interactions, along with three effective dynamical charges. The calculated results are compared and found to be in fairly good agreement with the available experimental and theoretical results. The elastic anisotropy of the studied compounds is analyzed and visualized by plotting three-dimensional surfaces representing the directional dependences of Young's modulus.

Density functional FP-LAPW+lo method calculations were performed to explore the structural, electronic, optical, elastic, thermoelectric and thermodynamic properties of the spinel oxides ZnRh2O4 and CdRh2O4. The exchange-correlation potential were described using the GGA-PBEsol and TB-mBJ functionals. As the first step, the optimized structural parameters, including the lattice parameter and atomic coordinates, were determined. Electronic band structure, atomic-resolved l-projected densities of electronic states and photon energy dependence of the linear optical functions were computed. It is found that both investigated compounds are indirect band gap semiconductors. The band gap results from the splitting of the R h : 4 d 6 states into occupied R h : 4 d − t 2 g 6 states, which form the valence band maximum (VBM), and the empty states R h : 4 d − e g 0 , which form the conduction band minimum (CBM), owing to the octahedral substantial crystal-field. The electronic interband transitions responsible of the structures in the optical spectra were specified. Single-crystal and polycrystal elastic moduli, wave sound velocities, Debye temperature, Pugh's indicator and indexes of elastic anisotropy were numerically estimated using total energy versus strain. FP-LAPW+lo band structure in combination with the standard Boltzmann transport theory were employed to calculate the thermoelectric parameters, including Seebeck coefficient, electrical and thermal conductivities and figure of merit. It is found that the title compounds are potential candidates for thermoelectric applications if one can further reduce their thermal conductivities via some techniques. FP-LAPW+lo approach in combination with the quasi-harmonic Debye model was employed to study temperature and pressure dependences of some macroscopic physical parameters. Our obtained results in the present work are discussed in comparison with the available experimental and theoretical data. The calculated results show a good agreement with the available experimental and theoretical results.

To investigate the structural, elastic and electronic properties of the tetragonal inter-alkali metal chalcogenides CsNaX (X = S, Se, and Te), we have applied the full-potential linearized augmented plane-wave plus local orbital (FP-LAPW + lo) method within the density functional theory (DFT) framework. For the description of the exchange-correlation potential, the Wu-Cohen generalized gradient approximation (WC-GGA) was employed. Furthermore, the generalized gradient approximation of Engel and Vosko (EV-GGA) and Tran-Blaha modified Becke-Johnson (TB-mBJ) potential were also applied to obtain reliable results for the electronic properties of CsNaX compounds. Our optimized equilibrium structural parameters are in good agreement with experimental measurements where available. The Young's modulus, bulk modulus, shear modulus, Poisson's ratio, Pugh's ratio, acoustic velocities and Debye temperature were derived from our estimated elastic constants C i j . It is found that all the considered compounds are mechanically stable and ductile in nature. In addition, the elastic anisotropy of the examined compounds was studied by visualizing the directionally dependent Young's modulus, shear modulus and compressibility, as well as by calculating some elastic anisotropy indices. Electronic properties, such as the band structure, density of states and the charge density, were analyzed in detail. Calculated band structures show that the studied materials are semiconductors with indirect band gaps (Z-Γ).

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 structural stability and optoelectronic properties of the ternary Ba1−xBexS alloys along with the pure binary compounds BaS and BeS in the rock-salt (B1) and zinc-blende (B3) phases were investigated by the density functional theory (DFT) within the full-potential linearized augmented plane wave (FP-LAPW) method implemented in the Wien2k package. The generalized gradient approximation of Wu and Cohen (WC-GGA) was used for the exchange-correlation potential (Vxc) to compute the equilibrium structural parameters, lattice constant (a), and bulk modulus (B). In addition to the GGA approach, the modified Becke-Johnson potential of Tran and Blaha (TB-mBJ) scheme coupled with the spin-orbit interaction was used to calculate the band gap energies. Results reveal that BaS, Ba0.75Be0.25S, and Ba0.5Be0.5S compounds are stable in the rock-salt phase, while Ba0.25Be0.75S and BeS are found to be stable in the zinc-blende phase. The computed results for the band structures and optical constants are compared with other available theoretical calculations and experimental measurements.

In this study, the full potential linearized augmented plane wave method with the GGA approximation was employed to study the structural, elastic, electronic and thermal properties of the novel intermetallic $$\hbox {REPt}_4\hbox {In}_{4}$$ (RE $$=$$ Eu, Gd, Tb, Dy, Ho) compounds. Our findings demonstrate that the equilibrium lattice parameters are in good agreement with the available experimental measurements. The elastic constants ( $$C_\mathrm{ij}$$ ) were also calculated to understand the mechanical properties and structural stability of the compounds. Furthermore, the density of states and the charge density distributions of the compounds were calculated to understand the nature of the bonding in the material. Our analysis of the calculated values of the Poisson’s ratio and the B/G ratio shows their ductile structure. Additionally, the temperature-dependent thermodynamic parameters are computed by the quasi-harmonic Debye model in the range of 0–600 K, where the primitive cell volume and thermal expansion coefficients have been obtained successfully. Consequently, this study on the structural, elastic, bonding and thermal properties of $$\hbox {REPt}_4\hbox {In}_4$$ intermetallic compounds demonstrate that these compounds can be used as potential candidates in the domain of energy storage and electronic devices.

Recently, 50-nm Heusler Mn3Al thin films were experimentally synthesized by Jamer et al. [Phys. Rev. Appl. (2017), 7, 064036] and the nominal zero moment, i.e. the fully compensated ferrimagnetic property, of these thin films was confirmed. That work motivated the current investigation on the martensitic transformation, electronic structure and magnetism of D03-ordered Mn3Al using first-principles calculations. Owing to tetragonal distortion, the martensitic transformation only occurs with tensile strain rather than with compressive strain and the half-metallic-type Mn3Al becomes a magnetic metal. Consequently, Mn3Al shows great potential for application as a ferromagnetic shape memory alloy. Moreover, not only did the martensitic transformation occur in Mn3Al, it was also observed in similar D03-ordered Mn3 Z (Z = B, Ga, Ge, Sb) compounds.

By using the full potential linearized augmented plane wave (FP-LAPW) method, the electronic properties of the layered BaAgChF (Ch = S, Se, Te) were investigated. Both the standard GGA and the TB-mBJ potential were used to model the exchange-correlation potential. To evaluate the spin-orbit coupling (SOC) effect, both the scalar relativistic and full relativistic calculations were performed. The SOC effect is found to be not negligible in the title compounds. The FP-LAPW band structure and the semi-classical Boltzmann transport theory were used to study the charge-carrier concentration and temperature dependences of the thermoelectric parameters, including Seebeck coefficient, electrical conductivity, thermal conductivity and figure of merit. Our results show that the values of the thermoelectric parameters of the p-type compounds are larger than that of the n-type ones. The optimal p-type doping concentrations and temperatures that yield the maximum values of the figure of merit of the title compounds were calculated. These are important parameters to guide experimental works.

The structural, electronic, optical and thermodynamic properties of the AlxIn1-xN (x = 0, 0.25, 0.50, 0.75 and 1) ternary alloys were investigated using the full potential linearized augmented plane wave (FP-LAPW) method in the framework of density functional theory (DFT). Optimized lattice parameter, bulk modulus and its pressure derivative were determined from suitable fit of the total energy versus volume with Murnaghan equation of state (EOS) for all considered alloys. Variations of the lattice parameter and bulk modulus with the Al concentration (x) deviate from Vegard’s law. Electronic band structure, dielectric function and refractive indices were investigated and computed for the considered alloys. It is found that the variations of the band gap, the static dielectric constant and static refractive index versus the Aluminum Al concentration obey to a quadratic polynomial. Temperature and pressure dependencies of the Gibbs free energy G, isochoric heat capacity CV, entropy S and Debye temperature θD were investigated via the Debye quasi-harmonic model for the Al0.5In0.5N ternary alloy. Furthermore, the elastic constants Cij, the bulk modulus B, Shear modulus G with Young modulus E and the Poison’s ratio v with the compressibility B/G were carried out in the cubic phase. Deduced results agree well with the available theoretical and experimental results.

First-principles density functional theory approach is adopted to determine the electronic, magnetic and structural characteristics of the Mn2CoAs1−xAlx (x = 0,0.25,0.50,0.75) Heusler alloys. The computations are carried out by WIEN2k code based on full-potential linearized augmented plane wave method (FP-LAPW). Moreover, the exchange-correlation energy functional is treated at the level of the generalized gradient approximation (GGA). Analysis of our computed results of the electronic band structure, as well as the density of states of the Mn2CoAs compound, show it a stable and half-metallic material with an energy band gap value of 0.48 eV. The calculated spin gap values are: 0.627 eV, 0.22 eV and 0.188 eV for Mn2CoAs0.75Al0.25, Mn2CoAs0.50Al0.50 and Mn2CoAs0.25Al0.75 respectively. Furthermore, the calculated total magnetic moment of the Mn2CoAs (4 µB) is found to be in agreement with the Slater–Pauling rule. Thus, our calculations show the Mn2CoAs1−xAlx (x = 0, 0.25, 0.50, 0.75) Heusler alloys potential materials for near future applications in spintronic because of their half-metallic ferromagnetism property.

A first-principles method has been employed to determine the electronic, magnetic and structural characteristics of the full-Heusler alloys Fe2VAl with Sn doping. All the calculations were performed by using a computational code based on full-potential linearized augmented plane wave method called WIEN2k. The electron exchange–correlation is treated by the generalized gradient approximation within a scheme developed by Perdew, Burke and Ernzerhof (PBE-GGA). The electronic band structures of Fe2VAl1−xSnx (x = 0, 0.25, 0.50, 0.75) compounds show that the majority-spin (spin-up) exhibits a metallic characteristic, whereas the minority-spin (spin-dn) have an energy band gap. Our calculations predict that Fe2VAl1−xSnx compounds are half-metallic ferromagnets with an integer value of magnetic moment, 0, 1, 2, and 3 μB, respectively. Our findings suggest that these materials are potential candidates for manufacturing spintronic devices.

In this study, first-principles investigations were performed using the full-potential linearized augmented plane-wave method of the structural and optoelectronic properties of thorium germinate (ThGeO4), a high-K dielectric material. Under ambient conditions, the structural properties calculated for ThGeO4 in the zircon phase were in excellent agreement with the available experimental data. Furthermore, using the modified Becke -Johnson correction method, the calculated band gaps and optical constants accurately described this compound. Finally, the thermal properties were predicted over a temperature range of 0–700 K and pressures up to 11 GPa using the quasi-harmonic Debye model, where the variations in the heat capacity, primitive cell volume, and thermal expansion coefficients were determined successfully.

Ab-initio calculations based on density functional theory have been performed to study the structural, electronic, thermodynamic and mechanical properties of intermetallic compounds Pt3Sc and Pt3Y using the full-potential linearized augmented plane wave(FP-LAPW) method. The total energy calculations performed for L12, D022 and D024 structures confirm the experimental phase stability. Using the generalized gradient approximation (GGA), the values of enthalpies formation are −1.23 eV/atom and −1.18 eV/atom for Pt3Sc and Pt3Y, respectively. The densities of states (DOS) spectra show the existence of a pseudo-gap at the Fermi level for both compounds which indicate the strong spd hybridization and directing covalent bonding. Furthermore, the density of states at the Fermi level N(EF), the electronic specific heat coefficient (γele) and the number of bonding electrons per atom are predicted in addition to the elastic constants (C11, C12 and C44). The shear modulus (GH), Young's modulus (E), Poisson's ratio (ν), anisotropy factor (A), ratio of B/GH and Cauchy pressure (C12–C44) are also estimated. These parameters show that the Pt3Sc and Pt3Y are ductile compounds. The thermodynamic properties were calculated using the quasi-harmonic Debye model to account for their lattice vibrations. In addition, the influence of the temperature and pressure was analyzed on the heat capacities (Cp and Cv), thermal expansion coefficient (α), Debye temperature (θD) and Gruneisen parameter (γ).

We report the results of studies on the structural, electronic and optical properties of MgSi1−xGexAs2(x = 0, 0.25, 0.5, 0.75 and 1) using density functional theory (DFT) based on the full-potential linear augmented plane wave (FP-LAPW) method. To treat the exchange-correlation potential for the total energy calculations, the generalized gradient approximation (WC-GGA) by Wu-Cohen was used. Additionally, the modified Becke Johnson (mBJ) potential approximation, which successfully corrects the band-gap problem, was used for the band structure calculations. The calculated lattice constants and band-gap values for these alloys are in good agreement with the available theoretical and experimental data. A decrease in the band gap is observed with an increasing Ge content. The dielectric function and absorption coefficient are calculated to investigate the optical properties. Electronic and optical properties reveal that these alloys should be very useful for applications in photonics, optoelectronics and optics.

A systematic ab initio investigation has been performed to determine the elastic stability, the structural and finite-temperature thermodynamic properties of copper iodide (CuI) in the zinc-blende phase under pressure. All calculations are carried out based on the pseudopotential density functional method, in which we employ the generalized gradient approximation of the revised Perdew-Burke-Ernzerhof form and local density approximation of Ceperly and Adler parameterized by Perdew and Zunger together with plane-wave basis sets for expanding the periodic electron density. The obtained normalized volume dependence of the pressure and the equation-of-state parameters including equilibrium volume, isothermal bulk modulus and its pressure derivatives are in excellent agreement with the experimental data and other theoretical results. The elastic constants are calculated and the investigation of the mechanical stability from the elastic constants under pressure indicates that the zinc-blende CuI is stable up to 10 GPa. Through the careful evaluation with the quasi-harmonic Debye model in which the phononic effects are considered, a complete set of thermodynamic data up to 800 K, including the bulk modulus, volume thermal expansion coefficient, heat capacity, entropy, Debye temperature, and Gruneisen parameter of CuI with zinc-blende structure is achieved. This set of data is considered as the useful information to understand the high-temperature and high-pressure properties of CuI.

First-principles calculations were performed to investigate the structural, elastic, electronic, optical and thermoelectric properties of the Zintl-phase Ae3AlAs3 (Ae = Sr, Ba) using two complementary approaches based on density functional theory. The pseudopotential plane-wave method was used to explore the structural and elastic properties whereas the full-potential linearised augmented plane wave approach was used to study the structural, electronic, optical and thermoelectric properties. The calculated structural parameters are in good consistency with the corresponding measured ones. The single-crystal and polycrystalline elastic constants and related properties were examined in details. The electronic properties, including energy band dispersions, density of states and charge-carrier effective masses, were computed using Tran-Blaha modified Becke-Johnson functional for the exchange-correlation potential. It is found that both studied compounds are direct band gap semiconductors. Frequency-de...

The pressure-induced B3-B1 structural phase transition and some interesting thermodynamic properties for high-pressure B1 structure of cubic copper iodide (CuI) have been studied systematically using first-principles calculations based on density functional theory. It is found that CuI has a B3 ground-state phase at zero pressure and the transition pressure from B3 to B1 structure determined by the relative enthalpy versus pressure curves is about 6.9 GPa with a volume contraction of 14.42%. As a high-pressure phase, the B1 structure will be mechanically stable up to 57 GPa according to the generalized elastic stability criteria. Through the quasi-harmonic Debye model, the dependences of the primitive cell volume, isothermal bulk modulus, volumetric thermal expansion coefficient, heat capacity, entropy, and Debye temperature of CuI with high-pressure B1 phase on pressure and temperature are successfully predicted. The thermodynamic properties are summarized in the pressure range of 0–50 GPa and the temperature up to 800 K.

To find a seemly solution to the problems of efficiency dependency of the hybrid PV/TE devices, on important factors like “high-absorbance with high-ZT materials” and improving the performance of existing devices, are essential research topics nowadays. In this regard, we report here optical coating, and thermoelectric features of the kesterite-structured Ag2CdSnS4 and Ag2CdSnSe4 compounds. These investigations are performed at the level of “full-potential linearized augmented plane wave plus local orbital method, FP-L(APW + lo)” framed within the “density functional theory (DFT)” method comprised with relativistic effects. Our study of the optical coating shows that both the investigated materials have a good level of absorbance (A), approximately 80% in the visible part of the spectra. Further, we found that the magnitude of reflectance (R) of the Ag2CdSnX4 (X = S, Se) thin films increase with increasing film thickness, while the response of the transmittance (T) spectra is reverse to it. These results are corroborated by the study of the transport properties by employing the Boltztrap code, and correspondingly electrical conductivity, Seebeck coefficient, electronic thermal conductivity as well as the figure of merit parameters were evaluated and analyzed as a function of the chemical potential for both investigated compounds at five values of the temperatures. Hence our obtained results show that both the investigated semiconductor materials exhibit strong potential for the application of hybrid PV/TE systems.

We report and discuss the results of a detailed ab initio investigation of the structural, elastic, electronic and optical properties of a new layered perovskite-type oxyfluoride: CsSrNb2O6F. The calculated ground state lattice parameters are in excellent agreement with the available experimental counterparts. The six predicted distinct single-crystal elastic constants satisfy the mechanical stability criteria. From the calculated single-crystal elastic constants, a set of related properties, viz., the bulk modulus, shear modulus, Young’s modulus, anisotropic and isotropic sound velocities, elastic anisotropy, malleability and Debye temperature, are determined. The title compound is found to be ductile with strong elastic anisotropy. Considering that the measured values are always determined with uncertainties of various origins, one can state that the calculated fundamental indirect bandgap value of ~2.9 eV and the onset of direct optical transitions at ~3.6 eV are in acceptable agreement with a prior measurement giving a bandgap of ~3.4 eV. Particular attention has been given to the bonding properties and distribution of the electron density in the space between the crystal lattice ions through the calculation of density of states diagrams, bond lengths and the charge density distribution. The linear optical parameters of the considered compound, including the complex dielectric function, absorption coefficient, refractive index and optical reflectivity, are predicted for incident electromagnetic radiation polarized parallel to the [100] and [001] crystallographic directions. It is noted that CsSrNb2O6F exhibits a strong optical anisotropy.

First principles calculations were carried out on the SrMoO4 compound which has been of interest owing to its technologically important physical properties. The structural, electronic, optical and thermal properties of this compound have been investigated under low pressure (LP) through the full potential linearized augmented plane wave method (FP-LAPW) within the framework of density functional theory. It is found that the phase transition from zircon to scheelite type structure occurs at negative pressure. The calculated ground state properties in scheelite structure are found to be in good accord with previously published data. Using the recently developed Tran Blaha-modified Becke Johnson approach, we have also studied the electronic band structure of this compound which shows the semiconducting behavior with a direct band gap of 4.30 eV in the scheelite phase, whereas the band gap is found to be 2.18 eV in the zircon phase. Various thermodynamic properties including the thermal volume expansion coefficient and heat capacities at constant volumes and pressures were calculated via the quasi-harmonic Debye model at different temperatures (0–1000 K). Furthermore, optical properties such as complex dielectric function, refractive index, and reflectivity spectra of the titled compound were studied for incident electromagnetic waves in an energy range up to 16 eV. The contributions to various transitions peaks in the optical spectra are analyzed and discussed with the help from the energy dependent imaginary part of the dielectric function.

Here in we have reported on band-structure calculations, within First principles density functional theory (DFT) based calculations are performed for the investigation of the electronic and optical properties of silver lanthnide dichalcogenides XAgSe2 ( X = Eu and Er). The current calculations (DFT) possess an admirable correspondence of the total density of states with the optical properties using the generalized gradient approximation. Additionally, the spin–orbit coupling (SOC) effect and Hubbard correction parameter U (GGA + SOC + U), (GGA + U) that is useful for the strongly correlated electron system The basic optical constants are calculated within the GGA + SOC + U technique and they expose a big viewpoint of using the XAgSe2 ( X = Eu and Er) compound in optoelectronic appliances.

In this theoretical study, we have investigated the structural, phase transition, electronic, thermodynamic and optical properties of GaPxSb1−x ternary alloys. Our calculations are performed with the WIEN2k code based on density functional theory using the full-potential linearized augmented plane wave method. For the electron exchange-correlation potential, a generalized gradient approximation within Wu–Cohen scheme is considered. The recently developed Tran–Blaha modified Becke–Johnson potential has also been used to improve the underestimated band gap. The structural properties, including the lattice constants, the bulk moduli and their pressure derivatives are in very good agreement with the available experimental data and theoretical results. Several structural phase transitions were studied here to establish the stable structure and to predict the phase transition under hydrostatic pressure. The computed transition pressure (Pt) of the material of our interest from the zinc blende (B3) to the rock salt (B1) phase has been determined and found to agree well with the experimental and theoretical data. The calculated band structure shows that GaSb binary compound and the ternary alloys are direct band gap semiconductors. Optical parameters such as the dielectric constants and the refractive indices are calculated and analyzed. The thermodynamic results are also interpreted and analyzed.

We report a detailed investigation of the elastic moduli, electronic band structure, density of states, chemical bonding, electron and hole effective masses, optical response functions and thermoelectric properties of the lead-free halide double perovskites Cs2AgBiCl6 and Cs2AgBiBr6 using the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA-PBEsol) and the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential. Because of the presence of heavy elements in the studied compounds, we include the spin–orbit coupling (SOC) effect. Our calculated structural parameters agree very well with the available experimental and theoretical findings. Single-crystal and polycrystalline elastic constants are predicted using the total-energy versus strain approach. Three-dimensional representations of the crystallographic direction dependence on the shear modulus, Young’s modulus and Poisson’s ratio demonstrate a noticeable elastic anisotropy. The TB-mBJ potential with SOC yields an indirect band gap of 2.44 (1.93) eV for Cs2AgBiCl6 (Cs2AgBiBr6), in good agreement with the existing experimental data. The chemical bonding features are probed via density of states and valence electron density distribution calculations. Optical response functions were predicted from the calculated band structure. Both of the investigated compounds have a significant absorption coefficient (∼ $$ 25 \times 10^{4} \;{\hbox{cm}}^{ - 1} $$ ) in the visible range of sunlight. The thermoelectric properties of the title compounds were investigated using the FP-LAPW approach in combination with the semi-classical Boltzmann transport theory. The Cs2AgBiCl6 and Cs2AgBiBr6 compounds have a large thermopower S, which makes them potential candidates for thermoelectric applications.

The structural phase transition and thermodynamic properties of CdN under high pressure and temperature are investigated by first-principles calculations based on the plane-wave pseudopotential density functional theory method combined with the quasi-harmonic Debye model. It can be found that the rocksalt phase of CdN is more stable than the zincblende phase in the pressure range of 0–100 GPa based on the enthalpy versus pressure relations. The variations of the volume, thermal expansion, specific heat, entropy, and Debye temperature with pressure and temperature of CdN in rocksalt structure are obtained systematically for the first time.

The Wang-Landau Monte Carlo algorithm, implemented within an effective Hamiltonian approach, is used to investigate the effect of mechanical and electrical boundary conditions on electrocaloric (EC) properties in (Ba 0.50 Sr 0.50 )TiO 3 thin films. The results indicate that the EC response maximizes near the paraelectric-to-ferroelectric (respectively, ferroelectric-to-ferroelectric) phase transition is suppressed (respectively, enhanced) by activating the depolarizing field inside the films. On the other hand, the EC response shows strong dependence on both the compressive and tensile strains. Interestingly, (Ba 0.50 Sr 0.50 )TiO 3 thin films are expected to show a giant EC effect near room temperature when the applied tensile strain is properly controlled. Our predictions also reveal that all observed phase transitions in the BST films are of second order and lead to an enhancement of refrigerant efficiency.

We report a systematic first-principles density functional theory study on the pressure dependence of the structural parameters, elastic constants and related properties and thermodynamic propertie...

We report the results of the full-potential linearized augmented plane wave (FP-LAPW) calculations on the structural, elastic, optoelectronic and magnetic properties of $$\hbox {CdHo}_{2}\hbox {S}_{4}$$ spinel. Both the generalized gradient approximation (GGA) and Trans-Blaha modified Becke-Johnson potential (TB-mBJ) are used to model the exchange-correlation effects. The computed lattice parameter, internal coordinate and bulk modulus are in good agreement with the existing experimental data. According to the calculated elastic moduli, $$\hbox {CdHo}_{2}\hbox {S}_{4}$$ is mechanically stable with a ductile nature and a noticeable elastic anisotropy. The ferromagnetic phase of $$\hbox {CdHo}_{2}\hbox {S}_{4}$$ is energetically favourable compared to non-magnetic one, with a high magnetic moment of about 8.15 $$\upmu _{\mathrm{B}}$$ . The calculated band structure demonstrates that the title compound is a direct band gap semiconductor. The TB-mBJ yields a band gap of $$\sim $$ 1.86 and $$\sim $$ 2.17 eV for the minority and majority spins, respectively. The calculated optical spectra reveal a strong response in the energy range between the visible light and the extreme UV regions.

Ab initio calculations based on the density functional theory within the full-potential linearized augmented plane wave method were carried out to investigate the structural stabilities of the different crystallographic phases, the pressure-induced phase transition and the electronic properties of the platinum carbide (PtC) compound. The zinc-blende (ZB), rock-salt (RS), cesium chloride (CsCl), wurtzite (WZ), nickel arsenide (NiAs), lead monoxide (PbO) and the tungsten carbide (WC) phases were considered. The exchange and correlation potential was treated by the generalized-gradient approximation using the Perde–Burke–Ernzerhof parameterization. The thermodynamic properties such as variation of the bulk modulus, lattice constant, heat capacity, thermal expansion and Debye temperature versus pressures and temperatures are investigated. The band structure results show the metallic character of the PtC compound in all the considered phases and the present study also shows that the PtC compound crysta...

The structural, elastic, and electronic properties of rare earth intermetallic R2Ni2Pb (where R = Ho, Lu, and Sm) compounds were investigated with the density functional theory (DFT) calculations. The calculations are performed using the full potential-linearized augmented plane wave (FP-LAPW) method within the framework of local density approximation (LDA). The calculated values of the equilibrium lattice constants were in agreement with the available experimental values. The elastic constants (C i j ) were also calculated to understand the mechanical properties and structural stability of the compounds. Furthermore, the density of states and the charge density distributions of the compounds were calculated to understand the nature of the bonding in the material. The calculated results are in accordance with the available data in the literature.

The full-Heusler alloys Co2YZ (Z = P, As, Sb, and Bi) were investigated by using the state-of-the-art full-potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) method within the framework of density functional theory (DFT), to understand the structural, electronic, and magnetic properties of these new Heusler alloys. The generalized gradient approximation (GGA) was chosen to define the exchange-correlation potential for studying the structural properties, whereas electronic and magnetic properties were developed by using the GGA + U scheme, where U is the Hubbard term, which explains the Coulomb repulsion and was applied to describe the “d” electrons. The structural properties indicated that the ferromagnetic states of these compounds are energetically more favorable than the paramagnetic states. Through results on the electronic structures (band structures and densities of states), it is found that all these alloys exhibit a complete half-metallic nature, with half-metallic gaps (EHM) of 0.632, 0.605, 1.223, and 0.922 eV for Co2YP, Co2YAs, Co2YSb, and Co2YBi alloys, respectively. The magnetic properties indicated that the total spin magnetic moments of these Heusler alloys obey the Slater-Pauling rule around value 2 µ B approximately. The local magnetic moments of Co and Y transition elements have opposite signs with different intensities, thus revealing the ferromagnetic character. Our study of both electronic and magnetic properties demonstrates in detail that Co2YZ (Z = P, As, Sb, and Bi) full-Heusler alloys are complete half-metallic ferrimagnetic materials.

The structural, electronic and optical properties of the cubic RbMF3 perovskites (M = Be, Mg, Ca, Sr, Ba) have been investigated using the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange and correlation potential was applied using the generalized gradient approximation for calculating the structural properties In addition, the modified Becke-Johnson (TB-mBJ) potential was used for calculating the electronic and optical properties. It was found that the lattice constant increases while the bulk modulus decreases with the change of cation (M) in going from Be to Ba in the RbMF3 perovskites (M = Be, Mg, Ca, Sr, Ba). The reflectivity and absorption properties were also studied using the mBJ method to understand the inter-band transitions and their possible applications in absorption devices in the UV-region.

The structural phase transformations of the PtN compound with a 1:1 stoichiometric ratio of Pt:N were investigated using the framework of density functional theory (DFT). The full potential linearized augmented plane wave (FP-LAPW) method within the generalized gradient (PBE-GGA) and the Engel–Vosko generalized gradient (EV-GGA) approximations were used. A comparative study of the experimental and theoretical results is provided on the structural properties of zinc-blende (ZB), rock-salt (RS), cesium chloride (CsCl), wurtzite (WZ), nickel arsenide (NiAs), lead monoxide (PbO), and tungsten carbide (WC) phases. The calculated band structure using the modified version of the Becke and Johnson (mBJ) exchange potential reveals the metallic character of the PtN compound. The present study also shows that the PtN compound crystallizes in the WZ phase under ambient conditions. The theoretical transition pressures from WZ to RS, NiAs, PbO, and CsCl transformations are found to be 9.441 GPa, 7.705 GPa, 18.345 GPa and 31.9 GPa, respectively, using the PBE-GGA method.

In this work, the full-potential linearized augmented plane wave (FP-LAPW) method was used to calculate the structural, electronic, thermal and thermodynamic properties of BaS and CaS compounds and their ternary mixtures, Ba 1−x Ca x S. The local-density approximation (LDA), the Wu-Cohen generalized gradient approximation (WC-GGA) and the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) were used as the exchange-correlation potential. Moreover, the modified Becke–Johnson approximation was also used for the band structure calculations. We examined the composition effect on the lattice constants, bulk modulus and band gap. The microscopic origins of the band gap bowing were characterized in detail using the approach of Zunger and colleagues. Pressure and temperature effects on the lattice parameter, heat capacity, Debye temperature, Gruneisen parameter, and thermal expansion coefficient were predicted using the quasi-harmonic Debye model. The thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing, ∆H m , and the phase diagram. It was shown that these alloys are stable at high temperature.

First-principles density functional calculations were performed to investigate the structural parameters, elastic moduli and related properties, electronic band structure and optical properties of three LaOAgS-type barium silver fluoride chalcogenides BaAgChF (Ch denotes the chalcogenides S, Se and Te). The calculated structural parameters are in good accordance with the existing experimental data. The single-crystal and polycrystal elastic moduli were determined via the strain–stress technique. The investigated compounds show a strong anisotropic behaviour of the structural and elastic parameters. The calculated electronic band structure using the Tran–Blaha modified Becke–Johnson potential reveals that the three considered systems are large direct band gap semiconductors. The assignments of the energy band electronic states and chemical bonding character were accomplished with the help of the l-decomposed atomic densities of states diagrams. Frequency-dependent polarized optical functions were computed for an energy range from 0 eV to 30 eV. The microscopic origin of the electronic states that is responsible for the optical spectra structures were determined. The optical spectra exhibit a considerable anisotropy. Several trends in the variation of the considered physical properties with the atomic number Z of the chalcogenide Ch element in the BaAgChF series are observed.

Ab initio calculations based on density functional theory using the full-potential linearized augmented plane wave method have been carried out to find the structural stability of different crystallographic phases, the pressure-induced phase transition and the electronic properties of the magnesium chalcogenides MgS, MgSe and MgTe. The zinc blende (B3), wurtzite (B4), rock salt (B1), CsCl (B2), NiAs (B8), β-BeO, 5-5 and TiP crystal structures are considered and the exchange and correlation potential is treated by the generalized-gradient approximation using the Perdew–Burke–Ernzerhof parameterization. Moreover, the modified Becke-Johnson (mBJ) scheme is also applied to optimize the corresponding potential for the band structure calculations. Results show that the wurtzite phase is the stable structure in the ground state adopted by MgSe and MgTe compounds while MgS adopts the rock-salt one. Moreover, the band structure calculations reveal a metallic behavior in the CsCl structure for all the compo...

Lattice dynamics calculations have been performed for ternary chalcopyrite compounds CuAlS2, CuGaS2, CuInS2, and AgGaS2 using the proposed theoretical model. This model is applied to study the zone-centre (GAMMA = 0) phonon frequencies of CuAlS2, CuGaS2, CuInS2, and AgGaS2. The interatomic interactions up to third nearest neighbours were calculated. The calculated zone-centre phonon frequencies are found to be in very good agreement with observed and previous calculated data available in the literature. Single crystal elastic constants and related properties for these materials were also calculated and compared with the available data in the scientific literature.

In this paper, we have theoretically explored the structural, electronic and optical properties of the zinc blende structure of ternary alloys using the full-potential linearized augmented plane wave (FP-LAPW) method within the density-functional theory (DFT) as implemented in the Wien2 K code. The electronic properties were computed using the following two approximations: the generalized gradient approximation (GGA) and the Tran-Blaha-modified Becke-Johnson potential (TB-mBJ). The obtained results clearly show that ternary alloys exhibit large and direct band gaps while binary compounds are indirect band gap semiconductors.

A first-principles-derived effective Hamiltonian approach is used to reveal the temperature-versus-misfit strain phase diagram of an epitaxial (Ba 0.50 Sr 0.50 )TiO 3 dot under different electrical boundary conditions. The results indicate that the electrical polarization and toroidal moment are highly sensitive to the applied strain and/or electrical boundary conditions, resulting in a wide variety of phases that are not found in a free-standing BST dot and in bulk. The calculations indicate that within a narrow range of surface charge screening an intermediate phase in which the polarization and toroidal moment coexist. The dependences of the electrical polarization, toroidal moment and dielectric permittivity on the misfit strain and electrical boundary conditions at room temperature are also investigated and compared with the available theoretical predictions and experimental measurements.

Structural parameters, electronic structure and optical properties of the dialkali metal monotelluride M2Te (M = Li, Na, K and Rb) compounds in the cubic antifluorite structure were investigated via ab initio calculations using the all electron linearized augmented plane wave approach based on density functional theory with and without including spin-orbit coupling (SOC). The exchange-correlation interactions were described within the PBEsol version of the generalized gradient approximation and Tran-Blaha modified Becke–Johnson potential (TB-mBJ). Optimized equilibrium lattice parameters are in excellent accordance with existing measured ones. Computed energy band dispersions show that the studied compounds are large band gap materials. Inclusion of SOC reduces the band gap value compared to the corresponding one calculated without including SOC. Determination of the energy band character and interatomic bonding nature are performed using the densities of states diagrams and charge density distribution map. Linear optical function spectra are predicted for a wide energy range and the origin of the dielectric function spectrum peaks are determined.

In this research work, a study on the structural, optoelectronic, and thermodynamics propertiesof the SnZrCH3 (CH = S, Se) compounds is presented. The study is performed by the “full potential linearized augmented plane wave plus local orbitals (FP-(LAPW + lo)) method framed within density functional theory (DFT). To treat with exchange-correlation energy/potential, different approximations; local density approximation (LDA), generalized approximation (GGA) by Wu and Cohen (WC) named as (WC-GGA) are used toestimate structural properties such as lattice constants, bulk moduli,and related results of pressure derivative.Besides that Engel Vosko's approach of GGA named as (EV-GGA) and Becke-Johnson modified form of exchange-correlation potential (mBJ-GGA) is also used to obtain reliable results of the electronic and optical properties. Our calculations of electronic band structures and density of states endorse both compounds of indirect bandgapnature withbandgap energy 1.054 eV and 0.531 eV for SnZrS3 and SnZrSe3, respectively at the level ofmBJ-GGA. Our calculations of the optical absorption parameters show the highest values of absorption coefficients in the ultraviolet (UV) region, attributed to localized Zirconium states lying in the lower region of the conduction band. Hence, our findings show that both SnZrS3 and SnZrSe3 compounds are potential candidates for photovoltaic applications.Moreover, the pressure effects on the lattice constants, heat capacities, thermal expansion coefficients, entropy, and Debye temperature are also explored using the quasi-harmonic Debye model.

In this work, the effect of the composition on the structural, electronic, elastic, optical and thermodynamic properties of the Ga1-xAlxAs1-yPy quaternary alloys are investigated using the full-potential augmented plane wave plus local orbitals (FP-APW + lo) approach in the density functional theory framework as embodied in the WIEN2k computational package. The fundamental physical properties of the cubic Ga1-xAlxAs1-yPy quaternary alloys, such as lattice constant, bulk modulus, energy band structure and elastic constants, are predicted for the first time. The obtained results show that the Ga1-xAlxAs1-yPy quaternary alloys are direct band gap semiconductors, while their parents; GaP, AlAs, and AlP binary compounds are indirect band gap semiconductors. It is found that the studied materials are of brittle character and ionic bonding nature. The static dielectric constant and static refractive index of the considered alloys are calculated and compared with the obtained results using empirical models. Pressure and temperature dependencies of some thermodynamic parameters of the title quaternary alloys are also investigated and discussed.

A theoretical model has been proposed to estimate the interatomic interactions until a fourth closest neighbor, the first Brillouin zone frequencies, Debye temperature, thermal conductivity, Raman and infrared inactive and active modes ofphonon, and elastic stiffness constants and correlatedcharacteristics of the zirconium-based pyrochlore structure compounds La2Zr2O7, Nd2Zr2O7, Sm2Zr2O7 and Eu2Zr2O7. The calculated results reveal that the bulk modulus, shear modulus, thermal conductivity, Debye temperature and Young’s modulus follows the trends La2Zr2O7 → Nd2Zr2O7 → Sm2Zr2O7 → Eu2Zr2O7. Furthermore, all the examined compounds are ductile and having elastically anisotropic properties. The low thermal conductivity of these compounds demonstrates that the considered materials are promosing candidate in the coating of thermal barrier material in the aerospace field.