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Bulk properties and near-critical behaviour of SiO2 fluid

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Green Eleanor C. R., Artacho E., Connolly J. A. D.,
Project Boiling of silicate liquids, II: a molecular dynamic and thermodynamic analysis
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Original article (peer-reviewed)

Journal Earth and Planetary Science Letters
Volume (Issue) 491
Page(s) 11 - 20
Title of proceedings Earth and Planetary Science Letters
DOI 10.1016/j.epsl.2018.03.015

Abstract

Rocky planets and satellites form through impact and accretion processes that often involve silicate fluids at extreme temperatures. First-principles molecular dynamics (FPMD) simulations have been used to investigate the bulk thermodynamic properties of SiO2 fluid at high temperatures (4000–6000 K) and low densities (500–2240 kgm−3), conditions which are relevant to protoplanetary disc condensation. Liquid SiO2is highly networked at the upper end of this density range, but depolymerises with increasing temperature and volume, in a process characterised by the formation of oxygen–oxygen (O=O) pairs. The onset of vaporisation is closely associated with the depolymerisation process, and is likely to be non-stoichiometric at high temperature, initiated via the exsolution of O2 molecules to leave a Si-enriched fluid. By 6000 K the simulated fluid is supercritical. A large anomaly in the constant-volume heat capacity occurs near the critical temperature. We present tabulated thermodynamic properties for silica fluid that reconcile observations from FPMD simulations with current knowledge of the SiO2 melting curve and experimental Hugoniot curves.
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