RAMAN-STUDY AT HIGH-PRESSURE AND THE THERMODYNAMIC PROPERTIES OF CORUNDUM - APPLICATION OF KIEFFER MODEL

A Raman spectroscopic study was performed in a diamond-anvil cell to m easure the optical vibrational modes of corundum as a function of pres sure up to 20 GPa. The integrals concerning the optic continuum in Kie ffer's model can be calculated as the weighted sum of each mode in the continuum. Thus, on the basis of Kieffer's model and the experimental results of this study, thermodynamic parameters such as heat capacity , entropy, thermal expansion coefficient, and Gruneisen parameter for corundum at various pressures and temperatures were determined. The co ntribution to the heat capacity of corundum approaches the classic (Du long-Petit) limit in the interior of the Earth beneath a depth of 50 k m.