A thermodynamic method for computing thermal expansivity, α, versus T along isobars for silicate perovskite

Abstract

The value of α, the volume thermal expansivity, defined as (1/V₀)(∂V/∂T)_P, enters into many physical properties and thermoelastic identities. The importance of knowing the value of α of candidate materials for the Earth's mantle at P, T conditions of the lower mantle is well recognized. Attempts to find the high-T, high-P values of α for mantle minerals have been made by many researchers. Here we compute α for combinations of P and T and η, T(η = V/V₀) found throughout mantle conditions by a thermodynamic method where the high-pressure experimental data used are all contained in the thermoelastic parameters. The thermodynamic parameters are our beginning point. High-temperature experiments are explicitly used as the boundary conditions of differential equations arising from thermodynamic identities.