The SiO2 polymorphs: The equations of state and thermodynamic properties of phase transformations

Thermal equations of state have been derived for polymorphic forms of SiO₂ and values of \(\mathop \smallint \limits_0^P\) V _T dP have been tabulated. Available experimental data on the phase equilibria at high pressures and temperatures have been used with these equations to calculate the standard thermodynamic functions for the α-quartz-coesite and coesite-stishovite transformations. A study of sensitivity of calculated thermodynamical properties to uncertainties of phase equilibria data, initial data for elastic constants and equations of state has been carried out. The discrepancies between standard thermodynamic properties of these transformations calculated from phase equilibria data and solution calorimetry data still persist.