Phase transition and thermodynamic properties of Sr under high pressure

Abstract

We have performed the first-principles and classical molecular dynamics simulations to investigate the phase diagram and thermodynamic properties of Sr under high pressure and temperature. The obtained solid phase diagram of Sr, based on the quasi-harmonic approximation (QHA), is greatly supported by the available experimental data under low pressure. From the coexistence-phase molecular dynamics simulations, we also obtained the high-pressure melting curve of Sr which shows good agreement with the experiment. While, the experimentally observed β-Sn structure of Sr-III was found to be mechanically unstable according to our phonon dispersion calculations and evolutionary algorithm structure searches. We find that α-U phase (space group Cmcm) is energetically favorable and is the good candidate of Sr-III.