Ultra soft pseudo potential investigation of fundamental physical properties of CaXO3 (X=Sn and Hf) distorted perovskites: A reference study to the perfect perovskites

The structural, electronic and optical properties of CaXO3 distorted perovskites compounds have been investigated by employing the Vanderbilt Ultra Soft Pseudo Potential (US-PP) using the plane wave method (PW) within density functional theory (DFT) and the local density approximation LDA. The studies of the dependence with pressure of enthalpies have confirmed the excellent mechanical stability of these materials. We have found that these compounds have a direct band gaps (G–G). The (110) charge density contour show that these distorted compounds exhibit a zig zag electronic short chains in contrast of ideal perovskites presenting a perfectly aligned chains. Elastic–electronic correlation was established between Cij individual elastic constant and the bonding-anti bonding chemical bonds. After that, some above properties were studied under hydrostatic pressure effect. CaSnO3 perovskite was very sensitive towards pressure than CaHfO3. The reflectivity maximum of these materials occurs in the ultra-violet energy ranges, which indicate that these perovskites can serve in some technological applications. Optical anisotropy shows that the compound CaSnO3 is considered as more anisotropic than CaHfO3. Furthermore, anisotropy maximum was found to be according to [0 1 0] and [1 0 0] directions for CaHfO3 and CaSnO3, respectively.