Molecular dynamics of NaCl (B1 and B2) and MgO (B1) melting: Two-phase simulation

Abstract Melting of NaCl and MgO has been simulated with a two-phase molecular dynamics method at constant pressure using newly developed interaction potentials. Equations of state for NaCl and MgO simulated by molecular dynamics are in good agreement with available experimental data. Equations of state for MgO and NaCl were obtained by fitting simulated volumetric properties at pressures and temperatures up to 300 kbar and 3000 K (for NaCl) and 2000 kbar and 7000 K (for MgO). The pressure dependence of the melting temperature was predicted up to 1000 and 1400 kbar for NaCl and MgO, respectively. Crystallization and melting were observed without hysteresis. The simulated melting curve of NaCl is fully consistent with experimental measurements. The pressure dependence of the melting temperature of MgO is consistent with experimental data at 1 bar and previous theoretical estimations by Jackson (1977) and Ohtani (1983). The melting temperature of MgO is substantially higher than that determined by Zerr and Boehler (1994) (by 1000 K at 300 kbar) and substantially lower than that predicted by Cohen and Gong (1994) (by 1500 Kat 300 kbar). The melting temperature of MgO at the pressure of the core-mantle boundary is calculated to be 6900 ± 200 K. The procedures for simulation of melting of NaCl and MgO, starting from a calculation of the interatomic potential and ending with analysis of results, are identical.

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