Modification of Lu's (2005) high pressure model for improved high pressure/high temperature extrapolations. Part I: Modeling of platinum at high pressure/high temperature

Abstract Calphad description at high pressure is a very important topic. Several models have been proposed in the literature. The model proposed by Lu et al. (X.-G. Lu, M. Selleby and B. Sundman, Comput. Coupling Phase Diagr. Thermochem., 29 (2005) 49-55) is very convenient in many aspects. But it has been criticized for giving unphysical extrapolations in certain conditions. We show that this model is indeed suitable if additional constraints on several parameters are made in order to obtain consistent extrapolations when both high pressure and high temperature are considered. This revised model will be applied to the complete description of the Os–Pt system. In this first part, the thermodynamic assessment of platinum in both solid and liquid phases is presented. The use of DFT and phonon calculated data provided in the present work will be shown to be useful for the thermodynamic assessment. A consistent description of Pt at high pressure and temperature (equation of state) including the liquid phase and phase diagram is given for the first time.