We investigated double perovskite compounds of the form Sr$_2$XOsO$_6$ (X = Li, Na, Ca) using the fullpotential linearized augmented plane wave (FP-LAPW) method. For the exchange-correlation energy, Wu andCohen generalized gradient approximation (WC-GGA), Perdew, Burke and Ernzerhof GGA (PBE-GGA), Engel and Vosko GGA (EV-GGA), and GGA plus Hubbard U-parameter (GGA $+$ U) were used. The calculated structuralparameters are in good agreement with the existing experimental results. Calculation of different elastic constants and elastic moduli reveals that these compounds are elastically stable and possess ductile nature. The GGA $+$ Uapproach yields quite accurate results of the bandgap as compared with the simple GGA schemes. The density of states plot shows that Sr-4d, Os-5d and O-2p states predominantly contribute to the conduction and valence bands.Further, our results regarding to the magnetic properties of these compounds reveal their ferromagnetic nature. In addition, these compounds seem to possess half-metallic properties, making them useful candidates for applicationsin spintronics devices.

The structural parameters, elastic constants, electronic and optical properties of the bi-alkali antimonides (Na$_2$KSb, Na$_2$RbSb, Na$_2$CsSb, K$_2$RbSb, K$_2$CsSb and Rb$_2$CsSb) were calculated using state-of-the-art density functional theory. Different exchange-correlation potentials were adopted to predict the physical properties of these compounds. The calculated structural parameters are found in good agreement with the available experimental and theoretical results. All the compounds are mechanically stable. The compounds Na$_2$KSb, K$_2$RbSb, K$_2$CsSb and Rb$_2$CsSb have direct bandgaps, in which chemical bonding among the cations and anions is mainly ionic. Furthermore, the optical properties of these compounds are described in detail in terms of the dielectric function, refractive index, reflectivity, optical conductivity and absorption coefficient.

We report the results of the full-potential linearized augmented plane wave (FP-LAPW) calculations on the structural, elastic, optoelectronic and magnetic properties of CdHo$_2$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 experimentaldata. According to the calculated elastic moduli, CdHo$_2$S$_4$ is mechanically stable with a ductile nature and a noticeableelastic anisotropy. The ferromagnetic phase of CdHo2S4 is energetically favourable compared to non-magnetic one, with ahigh magnetic moment of about 8.15 $\mu$B. The calculated band structure demonstrates that the title compound is a direct bandgap 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 UVregions.

In this work, the first-principles computational study on the structural, elastic, electronic and optical propertiesof Y$_x$Ga$_{1−x}$As as a function of yttrium concentration ($x$) is presented. The computations are performed using the fullpotential linearized augmented plane wave plus local orbital method designed within density functional theory. Firstly,we performed our calculations on the most stable phases, NaCl and zinc blende, then their transition pressure for eachconcentration is determined and analysed. Our computed results for the zero yttrium concentration are found consistentwith the available experimental measurements as well as with theoretical predictions. Moreover, the dependencies of theseparameters upon yttrium concentration ($x$) were found to be non-linear.We also report computed results on electronic-bandstructure, electronic energy band gap results and density of states. A systematic study on optical properties to analyse itsoptoelectronic character and elastic properties is presented.

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 REPt$_4$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 ($C_{\rm ij}$) were also calculated to understand the mechanical properties and structural stability of the compounds. Furthermore, the density of states and the charge density distributionsof 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 REPt$_4$In$_4$ intermetallic compounds demonstrate that these compounds can be used as potential candidates in the domain of energy storage and electronic devices.

A number of ternary-semiconductor oxides have shown promise for potential applications in catalysis, thermoelectricity, optoelectronics and electrochemistry. In this work, the thermoelectric and optoelectronic properties of La$_2$Pd$_2$O$_5$ compound are studied by the full-potential linearized augmented plane wave method based on density functional theory. The electronic band structure shows an indirect band gap of 1.342 eV for La$_2$Pd$_2$O$_5$. Partial and total density of states indicate strong hybridization among different electronic orbitals. The upper part of the valence band is dominated by the Pd-d and O-p states, while the lower conduction band originates mainly from the Pd-d state. Dielectric functions including the imaginary and real parts, along with other optical constants, such as absorption coefficient, energy loss function, reflectivity and refractive index, have been reported for the first time. Thermoelectric properties, including electrical and thermal conductivity, Seebeck coefficient and power factor with variation in temperature are also presented and discussed using semi-classical Boltzmann transport theory for the first time for La$_2$Pd$_2$O$_5$. It has been found that La$_2$Pd$_2$O$_5$ has attractive optoelectronic and thermal properties that can make it a suitable candidate for efficient thermoelectric and optoelectronic device applications.

Owing to the fact of the AB$_2$O$_4$ spinel oxide’s chemical and thermal stability, and other intriguing properties make them suitable candidate materials for many applications, including chemical looping and catalytic reactions. To do our investigations, a short-range non-Coulomb potential theoretical model is used to calculate the zone-centre, elastic constants, infrared phonon mode frequencies, Raman phonon mode frequencies, velocities of the sound wave along the highly symmetric three crystallographic-axes and Debye temperature of the vanadium spinel oxides AV$_2$O$_4$ (A $=$ Mn, Fe and Zn). The preliminary results of our calculations show that the interaction inthe second neighbour (V–O) is much stronger than the interaction of the first neighbour (A–O). Moreover, from the analysis of the obtained results of elastic constants, the nature of the studied vanadium spinels are found to beductile.

We theoretically investigated the structural, elastic and mechanical properties of Ti–15Nb–$x$Ge alloys with $x = 0.8$, 1, 1.2, 1.4, 1.6 and 1.8 (wt%) compositions for the first time. Theoretical calculations were performed with thegeneralized gradient approximation (GGA) functional within density functional theory (DFT). We employed the Perdew–Burke–Ernzerhof (PBE) scheme and the virtual crystal approximation (VCA) in this study. We determined the elasticconstants, bulk, shear and Young’s moduli, Pugh ratio, Poisson’s ratio, universal anisotropy and hardness of all the alloys under varying Ge% concentrations. All studied compositions of the alloys show structural stability. Young’s modulivalues were obtained as 43 and 14.8 GPa for Ti–15Nb–0.8Ge and Ti–15Nb–1.8Ge alloys, respectively, which compare well to the Young’s moduli range of human cortical bone with 10–30 GPa. Except the Poisson’s and Pugh ratios, all other computed parameters of the alloys were found to decrease under increasing Ge concentrations. Further, all investigated alloys exhibit desired ductile mechanical behaviour of biomaterials and calculated hardness values of these alloys are satisfactory with the hardness of human teeth dentin.

Spin-coating technique is employed to deposit nanostructured zinc oxide (ZnO) doping aluminium (Al) on p-Si substrate. Atomic forces microscopy (AFM), X-ray diffraction (XRD), ultraviolet–visible (UV–Vis) and scanning electron microscopies (SEM) are utilized to investigate the influence of annealing temperature in the range of 200 to 600$^{\circ}$C on the morphological, optical, structural and topographical characteristics of Al NPs-doped ZnO (AZO) nanostructure. The average reflectance is proven by the reflectance spectra to be in the wavelength range of 200–1000 nm, and the absorption spectra provided the optical energy gaps of nanostructured AZO. Crystalline and grain size are correlatedwith annealing temperature variations, thus providing more homogeneous and covered surface morphology. Our resultsare nominated for future researches.

In this study, an analysis of the effect of Na substitution on the electronic, structural and thermoelectric (TE) properties of the Li$_2$CuAs material is presented. The study is performed by employing the full-potential linearized augmented plane wave plus local orbital method designed within the density functional theory. To carry out the calculations related to the band structure, generalized gradient approximation by Wu-Cohen (WC-GGA) in combination with Trans Blaha-modified Becke-Johanson mBJ (TB-mBJ) potential is employed. Our results at the level of the WC-GGA approach show that there is no bandgap, whereas, at the level of the TB-mBJ approximation, the material displays bandgap with Na substitution, which is found to be further increased with the increasing Na concentration. To understand the role of different electronic states on the bandgap structure, the total and partial densities of states are also analysed. Furthermore, the temperature effect on the Seebeck coefficient, electronic thermal conductivity, electrical conductivity, power factor and figure of merit are computed. Our obtained results of the TE properties of Li$_2$CuAs at different Na compositions suggest that this compound is a potential candidate for thermoelectricity.

Recently, photovoltaic solar cells have been revolutionized by adopting ABX$_3$ halide perovskite materials as photoabsorbers. In the recent past, lead halide perovskites have attracted significant research interest. However, owing to its toxicity, alternative lead-free materials are currently being actively sought. In this work, we report the computational results of the structural, electronic, optical and elastic properties of the unexplored lead-free halide fluoroperovskite material ASiF$_3$ (A = Li, Na, K and Rb) by means of first-principles calculations. The computed energetic and elastic properties assert that the formation of the ASiF$_3$ cubic systems is energetically favourable and mechanically stable. According to the results, LiSiF$_3$ and NaSiF$_3$ are indirect bandgap semiconductors, which are not appropriate for solar cell applications. The calculated elastic, electronic and optical properties indicate that KSiF$_3$ and RbSiF$_3$ alloys are isotropic and exhibit high ductility. They have reasonable direct bandgaps, a small effective mass and good light absorption, making them suitable for single-junction photovoltaic cells and other optoelectronic applications in the visible and UV regions of the electromagnetic spectrum.