Critical vaporization of MgSiO<sub>3</sub>.

Xiao, Bing; Stixrude, Lars · Proc Natl Acad Sci U S A · 2018

basic_science · Level V

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Abstract

Inhomogeneous ab initio molecular dynamics simulations show that vaporization of MgSiO<sub>3</sub> is incongruent and that the vapor phase is dominated by SiO and O<sub>2</sub> 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 ([Formula: see text] 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 O<sub>2</sub>.