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Liquid‐Vapor Coexistence and Critical Point of Mg 2 SiO 4 From Ab Initio Simulations
Author(s) -
Townsend Joshua P.,
Shohet Gil,
Cochrane Kyle R.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl089599
Subject(s) - vaporization , supercritical fluid , critical point (mathematics) , thermodynamics , equation of state , materials science , water vapor , physics , meteorology , mathematical analysis , mathematics
Hypervelocity impact‐driven vaporization is characteristic of late‐stage planet formation. Yet the behavior and properties of liquid‐vapor mixtures of planetary materials of interest are typically unknown. Multiphase equations of state used in hydrodynamic simulations of planet impacts therefore lack reliable data for this important phenomenon. Here, we present the first constraints on the liquid‐vapor critical point and coexistence phase boundary of Mg 2 SiO 4 computed from ab initio molecular dynamics simulations. We found that the vapor is depleted in magnesium and enriched in silica and oxygen, while the coexisting liquid is enriched in magnesium and depleted in oxygen, from which we infer vaporization is incongruent. The critical point was estimated from an equation of state fit to the data. The results are in line with recent calculations of MgSiO 3 and together confirm that extant multiphase equation of state (EOS) models used in planetary accretion modeling significantly underestimate the amount of supercritical material postimpact.