Melting Curve of MgO from First-Principles Simulations

First-principles calculations based on density functional theory, both with the local density approximation (LDA) and with generalized gradient corrections (GGA), have been used to simulate solid and liquid MgO in direct coexistence in the range of pressure $0\le p\le 135\mathrm{GPa}$. The calculated LDA zero pressure melting temperature is $T_m^{\mathrm{LDA}}=3110\pm 50\mathrm{K}$, in good agreement with the experimental data. The GGA zero pressure melting temperature $T_m^{\mathrm{GGA}}=2575\pm 100\mathrm{K}$ is significantly lower than the LDA one, but the difference between the GGA and the LDA is greatly reduced at high pressure. The LDA zero pressure melting slope is $dT/dp\sim 100\mathrm{K}/\mathrm{GPa}$, which is more than 3 times higher than the currently available experimental one from Zerr and Boehler [ Nature (London) 371, 506 (1994)]. At the core mantle boundary pressure of 135 GPa MgO melts at $T_m=8140\pm 150\mathrm{K}$.