Double spinel materials ABB'O4 emerge as an innovative class of oxides with promising technological applications. First-principles calculations are employed to explore the fundamental properties of the double spinel ZnFeSnO4. Its elasticity and dynamic stability are investigated using the pseudo-potential plane wave (PP-PW) method, while the full-potential linearized augmented plane wave (FP-LAPW) approach is used to study its electronic and magnetic properties. The results reveal favorable thermodynamic stability, mechanical robustness, and dynamical stability for ZnFeSnO4. Analysis using GGA + U (U = 6 eV) in the FP-LAPW framework predicts half-metallic ferromagnetism, a highly desirable characteristic for spintronic applications due to its potential spin-polarized currents. However, the use of the mBJ functional results in semiconducting character with bandgaps of 1.813 eV, and 1.524 eV for spin-up and spin-down, respectively. Hence, the outcomes of the computations pertaining to the electronic characteristics are contingent upon the selection of the exchange-correlation functional. Furthermore, the calculated low lattice thermal conductivity of ZnFeSnO4 indicates its potential suitability for thermoelectric applications.

In this paper, using the FP-LAPW technique as implemented in the Wien2k code, we have studied the structural, electronic, optical, and mechanical properties of strontium-based compound Sr2VRuO6. In this study, we explore the properties of Sr2VRuO6 using various approximations. We present the total energy versus energy, employing the Wu-Cohen-Generalized Gradients Approximation (WC-GGA) for both nonmagnetic and ferromagnetic states. To determine the stability of this material in cubic structure, the tolerance factor (t) and octahedral factor (μ) have been calculated. The lattice parameters of Sr2VRuO6 were determined, and subsequent calculations yielded the compressive modulus, Young's modulus, shear modulus, and Poisson's ratio in both two and three dimensions. Analyzing the band structure of Sr2VRuO6 within the mBJ-GGA approximation the half metallic character is observed with an indirect bandgap of 2.34 eV. In addition, the total and partial density of states, as well as charge density maps for Sr2VRuO6 have been calculated. Furthermore, we investigated the real and imaginary parts of the dielectric function as functions of energy for Sr2VRuO6. Additionally, the study delved into the variation of the refractive index, absorption coefficient, reflectivity, and energy loss with respect to energy for Sr2VRuO6.

In this study, the structural, elastic, vibrational, electronic, optical, thermodynamic, and thermoelectric properties of the chalcogenide ternary Y2ZnX4 (Y = In, Ga; X = S, Se) compounds are comprehensively investigated using the pseudopotential plane-wave (PP-PW) and full-potential linearized augmented plane wave (FP-LAPW) methods. The analysis of elastic and vibrational properties reveals the dynamic and mechanical stability of these compounds. The calculated energy band gaps, ranging from 1.47 eV (Ga2ZnSe4) to 2.55 eV (In2ZnS4) in the visible spectrum, decrease as X atoms are substituted with S to Se. All examined compounds demonstrate favorable optical absorption (α > 105 cm-1) in the ultraviolet region. Notably, Ga2ZnSe4 exhibits absorption red-shift towards the visible region at hν = 2.76 eV due to its lower energy band gap, making it a promising candidate for solar cells. The three-dimensional representation of Young's modulus indicates significant deviation from sphericity, revealing anisotropic behavior in all compounds. Pugh's ratio, Poisson's ratio, and Cauchy's pressure analysis suggest ductile behavior in all four chalcogenide ternary compounds. Additionally, all compounds, except In2ZnS4, display auxetic properties. Finally, the calculated thermoelectric properties identify Ga2ZnS4 and In2ZnS4 as promising candidates for high-performance thermoelectric applications, with high Seebeck coefficients of 1848 and 1936 μV/K, respectively, and ZT values approaching unit.

First principles electronic structure calculations were performed on pure and chalcogenide doped GaNbO4. Doping with isoelectronic S and Se at the O sites in GaNbO4 shows a dopant site driven anisotropy in the structural properties which affects its electronic, optical and photocatalytic behavior. Band gap reduction in GaNbO4 is more with Se than S and this reduction can be regulated via choice of dopant, dopant site and dopant concentration. GaNbO4 bears an optical absorption profile similarity with anatase TiO2 (a-TiO2). Besides directional anisotropy, dopant induced absorption in the visible regime displays a site driven anisotropy, which, has implications on the onset of absorption and absorption peak heights. The visible region absorption peaks can be modulated with changes in the dopant concentration. Se dopant at a lower concentration gives a broader visible regime absorption peak of similar peak height as of a higher concentration S dopant. Undoped GaNbO4 has valence band maxima and conduction band minima at similar energies as a-TiO2 and these band placements can be altered through choice of dopant element, dopant site and dopant concentration to tune the visible light photocatalytic performance. Our study shows that doped GaNbO4 has a stronger visible range absorption than doped a-TiO2.

In this study, the electronic and structural characteristics of both bulk and monolayer hexagonal MoS2 material are studied within and beyond density functional theory (DFT) by considering one-shot GW corrections for an accurate band gap prediction. Interestingly, our computed quasiparticle (QP) bandgap of 1.36 eV and 3.33 eV for bulk and monolayer, respectively, is in excellent agreement with the experimental finding. The elucidation of the optical properties was estimated with the aid of the Bethe–Salpeter equation within the many-body perturbation theory (MPB). The computed optical transitions such as absorption coefficient, extinction coefficient, refractive index, reflectivity, and electron energy loss function are in better agreement with the experimental data. Moreover, the new approach allows for the efficient inclusion of all conduction bands in GW calculations, significantly reducing computational costs compared to traditional methods. A good agreement of the lattice parameters, as well as the interlayer distance with the experimental findings, is observed by the inclusion of van der Waals (vdW) corrections. Besides the agreement with previously reported values, the evaluated band structure determined with the quasiparticle corrections shows that both bulk and monolayer MoS2 material exhibit semiconducting properties with direct and indirect band gaps, respectively. The calculation of the density of states reveals that the s-orbitals of S atoms and the d-orbitals of Mo are predominantly at the origin of the essential material properties secured at the Fermi level. The results of the study also point to the possibility of a foundation for creating physical structures with swift, decisive, directed, and long-range broadband photodetection capabilities.

Binary chalcogenides with small Reststrahlen bands in the far infrared and microwave region make them intriguing for IR sensors and radar communication purposes. In this study, we have theoretically investigated the structural, phonon, electronic, optical, IR optical and thermodynamic properties of NpX, where X = S, Se, and Te chalcogenides. The face-centered cubic structure is relaxed to determine the optimized lattice parameters which increased with an increase in the size of involving chalcogen atom. Band structure reveals their metallic nature. The significant contribution of d and f-states of Np and p-states of chalcogens in band formation is evident from the density of state plots. The detailed analysis of optical parameters including real and imaginary parts of dielectric constant and refractive index, optical conductivity, and optical loss exhibit high absorption in the IR region.

One of the fundamental challenges in calculating the optical properties of crystalline materials is the accurate description of exciton effects so as to make it computationally viable for studying large systems. We combine the modified Becke-Johnson (mBJ) exchange potential and bootstrap kernel (BSK) of time-dependent density functional theory (TDDFT) to compute the imaginary part of the dielectric function of a variety of semiconductors and insulators (Si, GaAs, NiO, TiO2, LiF, LiCl, SrTiO3 and NaMgF3). The results are compared with the experimental data available in the literature. We also compute their dielectric functions using the random phase approximations (RPA) to verify the effect of the BSK method on the optical spectra of these compounds. We conclude that TDDFT+BSK+mBJ calculations can determine the optical spectra of the solids in good agreement with the experimental data (except for small-energy gap materials such as Si and GaAs) with low computational cost, and using a fully ab initio procedure.

The pressure dependencies of the structural, electrical, elastic, optical, and thermoelectric characteristics of the Halide double perovskites (HDPs) Rb2CuSbX6 (X = Cl, Br, and I) compounds were computed using the FP-LAPW method within the density functional theory framework, under high pressure conditions. HDPs received a lot of attention due to their potential application in optoelectronic and thermoelectric devices. The Perdew-Burke-Ernzerhof (PBEsol-GGA) is used to investigate the structural properties of selected compounds, while the modified Becke-Johnson (mBJ) functional is used to obtain a better agreement between the calculated optoelectronic and electronic properties and experimental observations. The Born criteria and formation energy are explored for the stability of all selected HDPs. The elastic constants of cubic symmetry are investigated to determine the difference between ductile and brittle nature, anisotropy, and bulk modulus. The bandgaps for Rb2CuSbCl6, Rb2CuSbBr6, and Rb2CuSbI6 are 1.08 eV, 0.72 eV, and 0.33 eV, respectively. Decrease band gap with increase in pressure. The density of states plots under zero pressure exhibit a combination of ionic and covalent bonding, whereas an increase in pressure results in a reinforcement of covalent bonding. The absorption spectra are observed in the infrared region. All HDPs were further analyzed with respect to optical absorption, refractive index, and dielectric constants for the energy range 0–10 eV. Additionally, Boltzmann classical theory explains the lower lattice temperature, greater Seebeck coefficient, thermal conductivity, and electrical conductivity of HDPs, making them for thermoelectric applications.

In this study, we looked into a number of physical properties of alkali-bismuth compounds XBi2 (X = K, Rb), in the cubic Laves phase (symmetry Fd 3¯ m) using the density functional theory (DFT). The structural, elastic behavior along with Pugh's ratio, Poisson's ratio, Cauchy pressure, anisotropy indices, micro- and macro-hardness, thermo-physical properties such as Debye temperature, sound velocities, Grüneisen parameter, and melting temperature, electronic band structure, and optoelectronic properties has been explored. The computed ground-state lattice parameters and unit cell volume are in close accordance with the known theoretical and experimental findings. The elastic, thermo-physical, and optoelectronic properties of XBi2 (X = K, Rb) are investigated for the first time in this study. The computed elastic constants satisfied the mechanical stability criteria. The estimated Pugh's ratio, Poisson's ratio, and Cauchy pressure signify the ductility of the compounds. In order to understand the electronic properties, band structures and electronic energy densities of states have been explored. These compounds exhibit metallic characteristics in their electrical band structures. We have done a complete investigation on the reflectivity, absorption coefficient, refractive index, dielectric function, optical conductivity, and loss function of these metals. These compounds possess a low Debye temperature, thermal conductivity, and melting point. The optical absorption, reflectivity spectra and the refractive index of XBi2 (X = K, Rb) show that they can be used as solar reflector and ultraviolet absorber. The majority of the findings in this study are novel.

Elastic and lattice dynamical properties of fluoride structure PbF2, CdF2 and their mixed superionic conductors PbxCd1-xF2 have been calculated through a twelve parameter three-body shell model. The calculated elastic constants and the related properties, phonon density of states, phonon dispersion relations, variation of lattice specific heat with the absolute temperature are in good agreement with the available theoretical and experimental data. The obtained results of calculated elastic constants for the studied compounds PbF2, CdF2 and their mixed compound PbxCd1-xF2 are mechanically stable. The results of the elastic constants suggest that the above compounds are less compressible along the principle axis than their face and body diagonal. The results for bulk, shear and Young's modulus decreases as CdF2 → PbxCd1-xF2→ PbF2. The Pugh's ratio for the above compounds shows ductile behavior.