The melting curve of MgO from first principles simulations

TL;DR

This study uses first principles simulations to calculate the melting curve of MgO across a range of pressures, providing insights into its melting temperature and slope, with implications for planetary interior modeling.

Contribution

It presents new first principles calculations of MgO's melting curve using DFT with LDA and GGA, highlighting differences and high-pressure behavior.

Findings

LDA predicts a zero pressure melting temperature of 3110 K, aligning with experiments.

GGA predicts a lower melting temperature of 2575 K at zero pressure.

At 135 GPa, MgO melts at approximately 8140 K.

Abstract

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