Molecular dynamics study of the transport properties of perovskite melts under high temperature and pressure conditions

Evgeny A. Wasserman, David A. Yuen, James R. Rustad

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Abstract

The transport properties of perovskite melts by molecular dynamics in the temperature range from 3000 to 6000 K and pressure range from 5.1 to 78 GPa were studied. Shear viscosities, coefficients of self-diffusion, infrared absorption spectra, and vibrational densities of states were calculated. Shear viscosities were computed through generalized mean-squared displacement of momenta. Shear viscosity estimates ranged from 3 × 10-2 to 5 × 10-2 P and did not vary significantly with temperature. The activation energy found for shear viscosity was about 38 kJ/mol. Our results showed that the Stokes-Einstein relationship between shear viscosity and self-diffusion did not hold. Activation energies of 139, 184, and 166 kJ/mol found for self-diffusion of Mg, Si and O atoms, respectively, at 5 GPa agree with experimental estimates. For P > 15 GPa and T = 4500 K, activation volumes of 4.9, 2.9 and 1.3 cm3 were found. The main peaks of the infrared spectrum are shifted towards lower frequencies with increasing pressure, while the peak frequency of the density of states moves up for higher pressures. The shift of infrared absorption peaks is due to coordination changes of the silicon atoms from four- to five-fold and six-fold and has been observed experimentally. Changes of Si from four-fold coordination at P = 5 GPa to five- and six-fold coordinations at high pressure around 70 GPa were found.

Original languageEnglish (US)
Pages (from-to)373-384
Number of pages12
JournalEarth and Planetary Science Letters
Volume114
Issue number2-3
DOIs
StatePublished - Jan 1993

Bibliographical note

Funding Information:
This research has been supported by the National Science Foundation and by Army High Performance Computing Research Center.

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