A first-principles investigations of Lead-free SbPCa 3 inverse perovskite for structural, electronic and optical properties with different DFT methods

Lead free inverse perovskites are now subject of great interest due to their numerous applications. Density Functional Theory based first principles calculations are used to compute structural, elastic, mechanical, electronic and optical characteristics of SbPCa 3 . The optimized lattice constants of SbPCa 3 are 5.389 & Aring;, 5.327 and 5.324 & Aring; using PBE-GGA, WC-GGA and PBEsol exchange and correlation functionals respectively. structural properties are calculated by energy-volume optimization fitted by Birch-Murnaghan equation state. The mechanical parameters like Poisson's ratio, Pugh's ratio, Cauchy pressure and anisotropic ratio indicate that SbPCa 3 is brittle in nature. The under estimation of band gap with PBE-GGA and WC-GGA improved by taking WC-mBJ potential which is specially designed for perovskites. The band structure revealed that SbPCa 3 is a direct band gap material with energy gap of 0.736 eV (PBE-GGA), 0.666 eV (WC-GGA) 2.594 eV (WC-mBJ). The effect of spin-orbit coupling has also been checked due to the involvement of heavy elements. The different optical parameters like dielectric constant, optical conductivity, energy loss function, refractive index and reflectivity are calculated. The detailed study suggests that SbPCa 3 is a promising candidate for photovoltaic applications.