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Boiling of silicate liquids: a molecular dynamic and thermodynamic analysis

Applicant Connolly James A. D.
Number 146872
Funding scheme Project funding (Div. I-III)
Research institution Institut für Mineralogie und Petrographie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geochemistry
Start/End 01.01.2014 - 31.12.2015
Approved amount 242'281.00
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All Disciplines (5)

Discipline
Geochemistry
Geophysics
Astronomy, Astrophysics and Space Sciences
Material Sciences
Physical Chemistry

Keywords (6)

Molecular Dynamics; Silicate vaporization; Phase Equilibria; Giant impacts; Equation of state; Thermodynamics

Lay Summary (German)

Lead
Thermodynamic properties of liquid-saturated silicate vapor are of importance in planet and satellite forming processes associated with giant impacts. Silicate liquid-vapor phase fields lie at ~3000 K at 0.1 MPa and terminate at a critical point that is variously estimated to lie at 5000-15000 K and 0.2-4 GPa. The estimated conditions are inaccessible by present experimental techniques; therefore, this study will constrain these conditions through molecular dynamic super-computer simulations.
Lay summary

 

Für die Riesen-Impact-Hypothese der Mondentstehung dynamische Modellierung deutet darauf hin, dass die Staubscheibe würde in erster Linie des Schlagzusammengesetzt sein, doch die Erde und Mond sind chemisch ähnlich. Es wurde vorgeschlagen, Mond-Erde-System wurde von einer frühen Phase der Massenaustausch zwischen Proto-Erde und seine Staubscheibe homogenisiert. Das Silikat-Flüssig-kritischen Punkt definiert die niedrigste Temperatur, bei der solche Austausch könnte ohne chemische Fraktionierung zu nehmen. Kenntnis der Bedingungen des kritischen Punktes, der geschätzt wird, um bei Temperaturen von 5.000 bis 14.000 K und Drücken von 0,1-1 GPa liegt, ist für die Durchführbarkeit der Einführung nach einem Aufprall Homogenisierung. Diese Studie wird Super-Computer molekulardynamische Berechnungen verwenden, um das Siliciumdioxid Siedelinie und seinen kritischen Punkt beschränken.

Direct link to Lay Summary Last update: 12.12.2013

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
Bulk properties and near-critical behaviour of SiO2 fluid
Green Eleanor C. R., Artacho E., Connolly J. A. D. (2018), Bulk properties and near-critical behaviour of SiO2 fluid, in Earth and Planetary Science Letters, 491, 11-20.
A Primer in Gibbs Energy Minimization for Geophysicists
Connolly James A. D. (2017), A Primer in Gibbs Energy Minimization for Geophysicists, in Petrology, 25(5), 526-534.
Liquid-vapor phase relations in the Si-O system: A calorically constrained van der Waals-type model
Connolly James A. D. (2016), Liquid-vapor phase relations in the Si-O system: A calorically constrained van der Waals-type model, in JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS, 121(9), 1641-1666.

Collaboration

Group / person Country
Types of collaboration
Emilio Artacho/NanoGUNE Research Center, San Sebastian, Spain Spain (Europe)
- in-depth/constructive exchanges on approaches, methods or results

Associated projects

Number Title Start Funding scheme
162450 Boiling of silicate liquids, II: a molecular dynamic and thermodynamic analysis 01.01.2016 Project funding (Div. I-III)
162450 Boiling of silicate liquids, II: a molecular dynamic and thermodynamic analysis 01.01.2016 Project funding (Div. I-III)

Abstract

The thermodynamic properties of liquid-saturated silicate vapor are of importance to understanding planet and satellite forming processes associated with giant impacts. These properties determine: the relationship between impact energy and the consequent melting and thermal evolution (e.g., Benz et al. 1986, Stevenson 1987, Canup 2008); the development of the instabilities that cause debris disks to spread beyond the Roche limit at which point satellites may coalesce (e.g., Thompson & Stevenson 1988, Machida & Abe 2004, Ward 2012); and the chemical fractionation caused by the escape of silicate atmospheres (Genda & Abe 2003) or by interactions between a protoplanet and its disk (Pahlevan et al. 2011). Silicate liquid-vapor phase fields lie at ~3000 K at 0.1 MPa and terminate at a critical point or, more generally, a maxcondentherm that is variously estimated to lie at 5000-15000 K and 0.2-4 GPa (e.g., Stevenson 1987, Melosh 1990, Guillot & Sator 2007, Melosh 2007). Such conditions, which can be realized during giant impacts (e.g., Canup 2004), preclude direct experimental observation except at pressures on the order of a 1-10 Pa (e.g., Mysen & Kushiro 1988, Nagahara et al. 1994) or, most recently, by extraordinarily complex shock-wave experiments (Kraus et al. 2012).Thus an equation of state (EoS) is required to predict liquid-vapor phase equilibria and thermodynamic properties from the limited experimental data. To date, the only EoS suitable for this purpose is the M-ANEOS for SiO2 (Melosh 2007), but the M-ANEOS makes no provision for compositional degrees of freedom and does not provide the information on fluid speciation. Such information is essential for the evaluation of chemical (isotopic) fractionation effects. We propose to remedy these deficiencies by parameterizing a molecular equation of state to characterize silicate fluids in MgO-FeO-SiO2 system. Herein we demonstrate the feasibility of this approach by using the modified Redlich-Kwong EoS (deSantis et al. 1974) to predict properties and phase equilibria in the Si-O system to pressures (~1 GPa) that are adequate to complement the high-pressure predictive capacity of empirical Hugoniot equations and/or the M-ANEOS. To calibrate the EoS we propose a first-principle molecular dynamics study of silica fluids. This study will not only constrain the pressure-volume-temperature state and viscosity of low density silica liquid, but also locate the boiling curve at elevated pressure and address the issue of non-stoichiometric boiling. The nature and diversity of the problems to be addressed in this project require a dedicated researcher who is knowledgeable about phase equilibrium modeling of silicate melts, is facile with numerical methods, and is capable of quickly mastering the techniques required for ab initio and molecular dynamics simulations. The primary purpose of this proposal is therefore to obtain funding for a post-doctoral researcher (Eleanor Green) to fulfill this role. The proposed modeling is computationally intensive; for this reason, we also request funding to purchase four 48-core nodes for the Brutus cluster at the ETH.
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