Effects of pressure on diffusion and vacancy formation in MgO from non-empirical free-energy integrations

TL;DR

This study uses non-empirical free-energy integrations to compute vacancy formation, migration, and diffusion in MgO under pressures up to 140 GPa and temperatures up to 5000 K, showing good agreement with experimental data.

Contribution

It introduces a parameter-free molecular dynamics approach to accurately predict diffusion and vacancy formation in MgO across a wide pressure and temperature range.

Findings

Excellent agreement with experimental zero-pressure diffusion data.

High-pressure diffusion behavior aligns with the homologous temperature model.

Diffusion constants increase with pressure and temperature as predicted.

Abstract

The free energies of vacancy pair formation and migration in MgO were computed via molecular dynamics using free-energy integrations and a non-empirical ionic model with no adjustable parameters. The intrinsic diffusion constant for MgO was obtained at pressures from 0 to 140 GPa and temperatures from 1000 to 5000 K. Excellent agreement was found with the zero pressure diffusion data within experimental error. The homologous temperature model which relates diffusion to the melting curve describes well our high pressure results within our theoretical framework.