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Titel |
Vaporization of SiO2 and MgSiO3 |
VerfasserIn |
Bing Xiao, Lars Stixrude |
Konferenz |
EGU General Assembly 2017
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 19 (2017) |
Datensatznummer |
250152321
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Publikation (Nr.) |
EGU/EGU2017-17144.pdf |
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Zusammenfassung |
Vaporization is an important process in Earth's earliest evolution during which giant impacts are thought to have produced a transient silicate atmosphere. As experimental data are very limited, little is known of the near-critical vaporization of Earth's major oxide components: MgO and SiO$_2$. We have performed novel ab initio molecular dynamics simulations of vapor-liquid coexistence in the SiO$_2$ and MgSiO$_3$ systems. The simulations, based on density functional theory using the VASP code, begin with a suitably prepared liquid slab embedded in a vacuum. During the dynamical trajectory in the canonical ensemble, we see spontaneous vaporization, leading eventually to a steady-state chemical equilibrium between the two coexisting phases. We locate the liquid-vapor critical point at 6600 K and 0.40 g/cm$^3$ for MgSiO$_3$ and 5300 K and 0.43 g/cm$^$3 for SiO$_2$. By carefully examining the trajectories, we determine the composition and speciation of the vapor. For MgSiO$_3$, We find that the vapor is significantly richer in Mg, O, and atomic (non-molecular) species than extrapolation of low-temperature experimental data has suggested. These results will have important implications for our understanding of the initial chemistry of the Earth and Moon and the initial thermal state of Earth. |
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