Phase transition and elastic constants of CaO from first-principle calculations

The structural B1–B2 phase transition of CaO and the elastic properties of the B1 phase of CaO are investigated by ab initio plane-wave pseudopotential density functional theory method. The dependences of the elastic constants cij, the aggregate elastic modulus Bs and G, the elastic anisotropic parameter A, and the Debye temperature ΘD on pressure are successfully discussed. From the usual condition of equal enthalpies, we find that the structural B1–B2 phase transition of CaO occurs at 62.8 GPa, consistent with the experimental value 61 GPa. From our elastic constants of CaO under pressure, we find that the B1–B2 structural transformation occurs at about 178 GPa by the elastic instability, which is far higher than the transition pressure 62.8 GPa.