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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, B02204, doi:10.1029/2004JB003409, 2005

Vibrational and thermodynamic properties of MgSiO3 postperovskite

Jun Tsuchiya

Department of Chemical Engineering and Materials Science, Minnesota Supercomputing Institute for Digital Technology and Advanced Computation, University of Minnesota, Minneapolis, Minnesota, USA


Taku Tsuchiya

Department of Chemical Engineering and Materials Science, Minnesota Supercomputing Institute for Digital Technology and Advanced Computation, University of Minnesota, Minneapolis, Minnesota, USA


Renata M. Wentzcovitch

Department of Chemical Engineering and Materials Science, Minnesota Supercomputing Institute for Digital Technology and Advanced Computation, University of Minnesota, Minneapolis, Minnesota, USA


Abstract

Phonon dispersions and vibrational density of states of MgSiO3 postperovskite, the new high-pressure phase of MgSiO3 perovskite, are calculated as a function of pressure up to 180 GPa using density-functional perturbation theory. The calculated frequencies are then used to determine the thermal contribution to the Helmholtz free energy within the quasi-harmonic approximation. The equation of state and several thermodynamic properties of interest are derived and compared with those of perovskite. The overall thermodynamic properties of postperovskite are almost the same as those of perovskite under its stability conditions.

Received 26 August 2004; accepted 13 December 2004; published 4 February 2005.

Keywords: histogram; statistics; petrography; point counting; detrital thermochronology.

Index Terms: 3611 Mineralogy and Petrology: Thermodynamics (0766, 1011, 8411); 3620 Mineralogy and Petrology: Mineral and crystal chemistry (1042); 3919 Mineral Physics: Equations of state; 3924 Mineral Physics: High-pressure behavior; 3939 Mineral Physics: Physical thermodynamics; 3949 Mineral Physics: Thermal expansivity.

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Citation: Tsuchiya, J., T. Tsuchiya, and R. M. Wentzcovitch (2005), Vibrational and thermodynamic properties of MgSiO3 postperovskite, J. Geophys. Res., 110, B02204, doi:10.1029/2004JB003409.