Narrow Results

The first-principles study of cubic perovskites SmXO₃ (X = Al and Co) for elastic, mechanical and optical properties is done in the framework of density functional theory (DFT). Optimized structural parameters are obtained first to find mechanical and optical properties of the materials. These obtained structural parameters are in accordance with the published data. The cubic elastic parameters C${}_{11}$, C${}_{12}$ and C${}_{44}$ are then calculated by using generalized gradient approximation (GGA) as an exchange correlation functional in Kohn–Sham equations. Poisson’s ratio, shear modulus, Young’s modulus and anisotropic factor are deduced from these elastic parameters. These compounds are found to be elastically anisotropic and SmAlO₃ is brittle while SmCoO₃ is ductile. Their covalent nature is also discussed by using Poisson’s ratio. In addition, optical properties like absorption coefficient, extinction coefficient, energy loss function, dielectric function, refractive index, reflectivity and optical conductivity are studied. This study predicts that SmAlO₃ and SmCoO₃ are suitable for optoelectronic devices.

The Half Heusler alloy (HHA) MnCrP has been studied theoretically for structural, elasto-mechanical and phonon properties. The structure is optimized and the calculated structural parameters are close to the literature. This optimized data is used to estimate three independent second-order cubic elastic constants $C_{11}$, $C_{12}$ and $C_{44}$. The mechanical stability criteria are explored by these constants and further used to estimate the elastic moduli; Young’s, bulk and shear modulus. The mechanical parameters like Poisson’s ratio, Pugh’s ratio, anisotropic factor, Cauchy pressure, shear constant, Lame’s constants, Kleinman parameter are also calculated and discussed. Discussions reveal the ductile nature, ionic behavior, anisotropic nature and mechanical stability of MnCrP. The metallic nature, compressibility, stiffness and interatomic forces of material are also described. Furthermore, the Debye temperature, where the collective vibrations shifts to an independent thermal vibrations, is also calculated. Longitudinal and transverse sound velocities are also obtained to investigate the phonon modes of oscillation. These phonon modes confirm the stability of the alloy as no negative phonon frequencies in the phonon-dispersion curves. These curves are used to estimate the reststrahlen band where light reflects 100% and the suitability of material is checked for Far Infrared (FIR), photographic, optoelectronic devices and sensors.

The structural properties of Vanadium Ferrite VFe₂O₄ are reported for temperature range 0–1000 K using Density Functional Theory. A comparative study with the available experimental and theoretical data in the literature is also presented. Effects of temperature on lattice constant, volume and bulk modulus are deduced that with the increase in temperature, bulk modulus decreases and lattice constant slightly increases. This proves that the material VFe₂O₄ remains in the same cubic phase for temperature range 0–1000 K. In addition, the optical response is observed with six optical constants like absorption, reflectivity, eloss, dielectric functions, refraction and optical conductivity. Band structures and electronic density of states are also computed by using TB-mBJ potential. We hope that our findings would provide a help to experimentalists in fabricating VFe₂O₄ for temperature-sensitive optical devices.