Thermal expansion, heat capacity and Gr�neisen parameter of grossular at high temperature and high pressure

Abstract

The thermodynamic properties of grossular garnet (Ca3Al2Si3O12) were determined as a function of pressure and temperature in this study. With a numerical iterative procedure, the unit-cell volume, adiabatic bulk modulus, thermal expansion, heat capacity, and Gr�neisen parameters of grossular up to 25 GPa, 2000 K were extracted from experimental elastic wave velocities at high temperature and high pressure conditions. The calculated unit-cell volume and adiabatic bulk modulus agree well with the previous studies. The results imply that our calculated thermal expansion, heat capacity, and Gr�neisen parameters of grossular are all decrease with elevated pressure, and both thermal expansion and heat capacity show nonlinear pressure dependences. On the other hand, the Gr�neisen parameter shows a linear pressure dependence. The pressure derivative of thermal expansion display a regularity increase with temperature, while the pressure derivatives of heat capacity and Gr�neisen parameters display a rapid decrease at low temperature and a slow growth above ~1000 K.