High pressure induced structural, elastic and electronic properties of Calcium Chalcogenides CaX (X = S, Se and Te) via first-principles calculations

We present an ab initio study of the structural, elastic and electronic properties of CaX (X = S, Se and Te) compounds. In order to describe the properties of these materials rather well, the calculations were based on the DFT theory with generalized gradient approximation (GGA). In particular, our results for the pressure phase transition, elastic stiffness and band structures are in good agreement with the available experimental and theoretical results. We also presented the pressure dependence for all parameters. The generalized stability criteria show that CaSe and CaTe to be mechanically stable at pressures up to the transition pressure. The electronic band structure calculations suggest that these compounds are semiconductors at 0 GPa, in agreement with literature data. We discuss the pressure effect on the band gaps and the metallization phenomena. We investigated the bonding character of CaX in terms of electronic charge density and found out that the strong charge localization around the anion side.