THE GIBBS ENERGY FORMULATION OF α, γ, AND LIQUID FE2SIO4 USING GROVER, GETTING, AND KENNEDY'S EMPIRICAL RELATION BETWEEN VOLUME AND BULK MODULUS

Abstract

The empirical linear relation between the volume and logarithm of bulk modulus of metals, discovered by Grover, Getting, and Kennedy is taken as the basis for our equation of state. Recently, we have shown that we can use this equation of state to make accurate predictions of thermochemical and thermophysical properties at high pressure and high temperatures for MgO and the polymorphs of Mg2SiO4. Using the available experimental information, the equation of state is applied to the two polymorphs and the liquid form of Fe2SiO4 to develop a consistent dataset of their thermodynamic properties in the temperature range between 150 and 2500 K and pressure range between 1 bar 13 GPa. Using thermodynamic methods we are able to discriminate experimental data from different sources. The results presented here are compared with results obtained with modern databases. For (Mg1 - x,Fex)2SiO4 solid solutions around a pyrolitic composition, we conclude that bulk sound velocity is not a strong discriminator in selecting Gibbs energy formulations for Fe2SiO4 using one database versus another. This is in contrast to what we found for Mg2SiO4.