Ab Initio Investigation of a Possible Liquid-Liquid Phase Transition in MgSiO3 at Megabar Pressures

TL;DR

This study uses density functional molecular dynamics to investigate the possibility of a liquid-liquid phase transition in MgSiO3 at high pressures, finding no evidence of such a transition in simulations.

Contribution

The paper provides new computational insights into MgSiO3's phase behavior at megabar pressures, challenging previous experimental predictions of a liquid-liquid phase transition.

Findings

No signature of a liquid-liquid phase transition was observed in simulations.

Equation of state and shock Hugoniot curves were derived for MgSiO3.

Alternative interpretations of experimental results are discussed.

Abstract

We perform density functional molecular dynamics simulations of liquid and solid MgSiO3 in the pressure range of 120-1600 GPa and for temperatures up to 20000 K in order to provide new insight into the nature of the liquid-liquid phase transition that was recently predicted on the basis of decaying laser shock wave experiments [Phys. Rev. Lett. 108 (2012) 065701]. However, our simulations did not show any signature of a phase transition in the liquid phase. We derive the equation of state for the liquid and solid phases and compute the shock Hugoniot curves. We discuss different thermodynamic functions and by explore alternative interpretations of the experimental findings.