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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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