1. An internal energy-dependent model for the Grüneisen parameter of silicate liquids.
- Author
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Zhou, Yacong (Brooke), Goddard, William A., and Asimow, Paul D.
- Subjects
- *
MOLECULAR dynamics , *LIQUIDS , *SILICATES , *SHOCK waves , *EQUATIONS of state , *HEAT capacity - Abstract
We investigated the accuracy of the Mie-Grüneisen approximation, which treats the Grüneisen parameter (γ) as a one-parameter function of volume, for use in describing the thermal equation of state of a silicate liquid. For this study, we focused on a single composition: the diopside-anorthite eutectic, an Fe-free basalt analog that has been extensively studied by shock wave experiments. We tuned an empirical force-field to a small set of ab initio N - V - T molecular dynamics simulations to ensure that it reproduces pressure, heat capacity, and γ at high and low pressures. We then used empirical force-field molecular dynamics simulations in a larger system and for longer run times to ensure accurate extraction of γ at numerous N - V - E state points. To first order, the results show the expected volume-dependence for silicate liquids, with γ increasing as volume decreases. However, there are also significant and systematic variations of γ with internal energy (E) at constant volume. We propose a simple model form that captures the volume and E dependence of γ with only one more free parameter than a typical Mie-Grüneisen formulation. We demonstrate the utility of this new model for well-constrained fitting to sparse shock wave experiment data below 200 GPa, obtaining a marked improvement in the ability to simultaneously fit the pre-heated liquid Hugoniot and points substantially offset from this Hugoniot. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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