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Microscopic anharmonicity and equation of state of MgSiO 3 ‐perovskite

1996; American Geophysical Union; Volume: 23; Issue: 21 Linguagem: Inglês

10.1029/96gl02771

1944-8007

Philippe Gillet, François Guyot, Yanbin Wang,

Glass properties and applications

The effect of temperature on the Raman spectrum of MgSiO 3 ‐perovskite is investigated between 77 and 300 K. The data, combined with those obtained at high pressure, are used to infer microscopic anharmonic parameters ( a i ). It is shown that only two low‐frequency Raman modes are significantly anharmonic. The small volume dependency of the a i parameters allows a quasi‐harmonic calculation of the thermal pressure from a simplified density of states of the vibrational modes without other a priori informations. The calculated high‐temperature EOS reproduces to within ±0.4% the experimental molar volume obtained in the 0.1 MPa‐36 GPa and 77–2000 K range. A softening of a low‐frequency mode with decreasing temperature is also observed.