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

Abstract

In Part I of this paper, we have described a modification brought to the model of Lu (X.-G. Lu et al., Comput. Coupling Phase Diagr. Thermochem. 29 (2005) 49-55) in order to avoid extrapolation problems at high pressure and temperature. We now extend this approach to the study of a binary system: Os-Pt. For this, a complete description (equation of state) of Os at high pressure/high temperature is provided including the liquid phase. The thermodynamic assessment of the system Os-Pt has been carried out at ambient pressure by the Calphad method. All this study has been supported by first principles, special quasi-random structure (including under high pressure) and phonon calculations. Finally, using the high pressure description of metastable structures (hcp Pt and fcc Os), we have been able to obtain by extrapolation a complete description of Os-Pt system up to 500 GPa. Recent experimental data for Os-Pt system obtained up to 50 GPa at various temperatures up to 2300 °C may us allow to validate our modeling approach.