The study of structural phase transition (SPT) for divalent-metal oxides is important to geophysicist, particularly, under simultaneous high pressure and temperature conditions to mimic the earth core condition. Since complete ab initio calculations are, usually, accurate only at ambient condition, some simple approximate schemes have been employed to examine materials behaviors at such extreme conditions. In this regard, tight-binding energy model within the second-moment approximation (TB-SMA) is used to calculate cohesive energy, enthalpy, SPT and shock Hugoniot pressure volume relation for a test case of MgO. The parameters of the model for both (B1 and B2) phases were calculated using the self-consistent plane-wave pseudopotential density functional theory (PW-DFT) within the generalized gradient approximation (GGA). Good agreement with the first principles results and experiments confirms the applicability of the TB-SMA model to such ionic oxides.

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