Critical vaporization of MgSiO3

Abstract

Inhomogeneous ab initio molecular dynamics simulations show that vaporization of MgSiO3 is incongruent and that the vapor phase is dominated by SiO and O2 molecules. The vapor is strongly depleted in Mg at low temperature and approaches the composition of the liquid near the critical point. We find that the liquid–vapor critical temperature (6,600 ±150 K) is much lower than assumed in hydrodynamic simulations, pointing to much more extensive supercritical fluid after the Moon-forming impact than previously thought. The structure of the near-critical liquid is very different from what has been studied previously and includes a significant fraction (10%) of molecular species SiO and O2.