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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 Mg2SiO4 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 MgSiO3 and together confirm that extant multiphase equation of state (EOS) models used in planetary accretion modeling significantly underestimate the amount of supercritical material postimpact. Key Points: Mg2SiO4 vaporizes incongruently and produces Mg‐poor vapor and O2 and SiO‐enriched vaporCritical point occurs at lower density and temperature than commonly used multiphase EOSGiant impact simulations underestimate amount of supercritical material postimpact [ABSTRACT FROM AUTHOR]

ALEGRA is a multiphysics finite-element shock hydrodynamics code, under development at Sandia National Laboratories since 1990. Fully coupled multiphysics capabilities include transient magnetics, magnetohydrodynamics, electromechanics, and radiation transport. ALEGRA is used to study hypervelocity impact, pulsed power devices, and radiation effects. The breadth of physics represented in ALEGRA is outlined here, along with simulated results for a selected hypervelocity impact experiment. • ALEGRA is a multiphysics finite-element shock hydrodynamics code. • An ALEGRA simulation captures phenomenology from a previous gas gun experiment. • Multiphysics capabilities include electromagnetics and radiation transport. • A multiphysics simulation demonstrates electromagnetic induction during impact. [ABSTRACT FROM AUTHOR]