First-principles temperature-pressure phase diagram of magnesium

Abstract

Using first-principles interatomic potentials derived from generalized pseudopotential theory, high-temperature solid-phase stability and melting in magnesium have been studied through a combination of analytic statistical methods and molecular-dynamics simulation. Extending our previous work on the hcp-bcc phase line in the solid below 1000 K [Phys. Rev. B 48, 13 253 (1993)], a complete and accurate temperature-pressure phase diagram to 3500 K and 60 GPa has thereby been obtained. The rapidly temperature-dependent hcp-bcc phase line in the solid is predicted to end in a triple point on the melting curve near 1200 K and 4 GPa. Calculated melting properties at ambient pressure and the hcp-liquid melt line to 4 GPa are in good agreement with existing experimental data. The high-pressure, high-temperature hcp-bcc and bcc-liquid phase lines should be readily accessible to experimental investigation via the laser-heated diamond-anvil cell.