Thermal equation of state of CaIrO3 post-perovskite

Abstract

The pressure-volume-temperature (P-V-T) relation of CaIrO3 post-perovskite (ppv) was measured at pressures and temperatures up to 8.6 GPa and 1,273 K, respectively, with energy-dispersive synchrotron X-ray diffraction using a DIA-type, cubic-anvil apparatus (SAM85). Unit-cell dimensions were derived from the Le Bail full profile refinement technique, and the results were fitted using the third-order Birth-Murnaghan equation of state. The derived bulk modulus KT0 at ambient pressure and temperature is 168.3 ± 7.1 GPa with a pressure derivative K 0 T0 = 5.4 ± 0.7. All of the high temperature data, combined with previous experimental data, are fitted using the high-temperature Birch-Murnaghan equation of state, the thermal pressure approach, and the Mie-Grunei- sen-Debye formalism. The refined thermoelastic parameters for CaIrO3 ppv are: temperature derivative of bulk modu- lus ðoKT =oTÞ P =- 0.038 ± 0.011 GPa K -1 , aKT = 0.0039 ± 0.0001 GPa K -1 , oKT =oT ðÞ V =- 0.012 ± 0.002 GPa K -1 , and o 2 P=oT 2 �� V = 1.9 ± 0.3 9 10 -6