Ab initio study of effect of pressure on structural and elastic properties of CaX, X = {O, S, Se}

We present density function theory study of effect of pressure on structural, elastic and electronics properties of compounds CaX (X=O, S and Se) within the generalized gradient approximation. The results presented for transition pressure, elastic parameters and band structures are in good agreement with the available literature. We also present the effect of pressure on these parameters. The generalized stability criteria show that CaSe is not stable above pressure of 29GPa and all the material CaX are not stable at B2 phase. The materials are brittle at equilibrium but this changes with pressure change. They are also generally anisotropic; CaO(B1) was found to be Isotropic at pressure of 12.5GPa. Finally, the band-gap of all the material around (Γ - X) decreased with pressure, all the material became indirect band-gap semiconductor at high pressure and CaSe undergoes a semiconductor-metal transition at pressure of 68 GPa