Thermodynamic data for the phases in the CaSiO₃ system

We derived a thermodynamic dataset for the phases in the CaSiO₃ system including the wollastonite polymorphs (wollastonite-I, wollastonite-II, and pseudowollastonite), larnite (β-Ca₂SiO₄), CaSi₂O₅ (titanite-like), CaSiO₃ perovskite, and CaSiO₃ liquid by using the available data on thermochemical, thermophysical, and volumetric properties of the phases and phase equilibrium relations. A relatively large amount of experimental information which became available recently on the enthalpy, entropy, heat capacity, and volumetric properties of the low-pressure solid phases and the CaSiO₃ liquid was included in the evaluation. With the exception of the pressure-temperature-volume data for CaSiO₃ perovskite, experimental measurements for the high-pressure phases CaSi₂O₅ titanite-like and CaSiO₃ perovskite are entirely lacking. For these phases, we used estimates obtained with the method of quasi-harmonic lattice dynamic simulation with a parameterized interatomic potential. Our thermodynamic assessment using all these data in combination with the published phase equilibrium data up to 16 GPa and 3000 K has resulted in a dataset which can be used to calculate the phase relations in the system up to 20 GPa and 3000 K. Our work represents the first attempt to evaluate a complete set of thermodynamic properties including enthalpy, entropy, and heat capacity for the high-pressure phases CaSi₂O₅ titanite-like and CaSiO₃ perovskite.