Toward an accurate equation of state and B1-B2 phase boundary for magnesium oxide to TPa pressures and eV temperatures

TL;DR

This study uses advanced quantum Monte Carlo methods to accurately determine the equation of state and phase boundary of magnesium oxide at extremely high pressures and temperatures, providing benchmarks for theoretical models.

Contribution

It presents the first comprehensive quantum Monte Carlo calculations of MgO's EOS and phase boundary up to 1 TPa and 10,500 K, benchmarking density functional theory functionals.

Findings

PBEsol is identified as the optimal exchange-correlation functional.

Results agree with experimental data at low pressures.

Provides a reference for MgO's EOS and phase boundary at high pressures and temperatures.

Abstract

By applying auxiliary-field quantum Monte Carlo, we calculate the equation of state (EOS) and B1-B2 phase transition of magnesium oxide (MgO) up to 1 TPa. The results agree with available experimental data at low pressures and are used to benchmark the performance of various exchange-correlation functionals in density functional theory calculations. We determine PBEsol is an optimal choice for the exchange-correlation functional and perform extensive phonon and quantum molecular-dynamics calculations to obtain the thermal EOS. Our results provide a preliminary reference for the EOS and B1-B2 phase boundary of MgO from zero up to 10,500 K.