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.
Townsend, Joshua P., et al. "Liquid-Vapor Coexistence and Critical Point of Mg<sub>2</sub>SiO<sub>4</sub> From Ab Initio Simulations." Geophysical Research Letters, vol. 47, no. 17, Aug. 2020. https://doi.org/10.1029/2020gl089599
Townsend, Joshua P., Shohet, Gil, & Cochrane, Kyle R. (2020). Liquid-Vapor Coexistence and Critical Point of Mg<sub>2</sub>SiO<sub>4</sub> From Ab Initio Simulations. Geophysical Research Letters, 47(17). https://doi.org/10.1029/2020gl089599
Townsend, Joshua P., Shohet, Gil, and Cochrane, Kyle R., "Liquid-Vapor Coexistence and Critical Point of Mg<sub>2</sub>SiO<sub>4</sub> From Ab Initio Simulations," Geophysical Research Letters 47, no. 17 (2020), https://doi.org/10.1029/2020gl089599
@article{osti_1670755,
author = {Townsend, Joshua P. and Shohet, Gil and Cochrane, Kyle R.},
title = {Liquid-Vapor Coexistence and Critical Point of Mg<sub>2</sub>SiO<sub>4</sub> From Ab Initio Simulations},
annote = {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.},
doi = {10.1029/2020gl089599},
url = {https://www.osti.gov/biblio/1670755},
journal = {Geophysical Research Letters},
issn = {ISSN 0094-8276},
number = {17},
volume = {47},
place = {United States},
publisher = {American Geophysical Union},
year = {2020},
month = {08}}
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SHOCK COMPRESSION OF CONDENSED MATTER - 2019: Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter, AIP Conference Proceedingshttps://doi.org/10.1063/12.0000946