First-principles calculations to investigate structural, elastic, mechanical, electronic and optical characteristics of RbSrX3 (X = Cl, Br)

The inorganic cubic perovskites RbSrCl3 and RbSrBr3 have been studied for structural, phonon, elastic, mechanical, electronic and optical properties using first principles calculations based on Density Functional Theory. The structures are optimized and found stable with lattice constants 5.70 & Aring; and 6.00 & Aring; for RbSrCl3 and RbSrBr3 respectively. The stability is further validated by formation energy and phonon calculations. The bulk modulus, shear modulus, Young's modulus, Pugh ratio, Poisson ratio, Cauchy pressure and other parameters are calculated using elastic constants to endorse the mechanical stability. The electronic structure revealed that both under study materials are indirect wide band gap material with band gap of 7.74 eV (RbSrCl3) and 6.54eV (RbSrBr3) with TB-mBJ. The density of states are consistent to band structures. The optical parameters such as dielectric constant, refractive index, reflectivity, absorption, optical conductivity and energy loss are calculated in response to incident electromagnetic radiation up to 30eV for their potential use in optoelectronic devices.