In first-principles-based calculations of thermodynamic quantities "thermodynamic consistency" has not been guaranteed when applying disparate approximation methods to diverse phases such as, compounds, solid solutions, or liquids, constituting alloy phase diagrams. In this study, we performed tailored calculations for each phase in the Cu-Ni-Si system and verified consistency using phase equilibrium calculations and likelihood analysis. The resulting phase diagrams generally reproduced experimental ones, despite extreme sensitivity to minute free energy differences. Furthermore, likelihood analysis quantitatively demonstrated that free energy residuals fall within a narrow 1-2 kJ/mol range. This indicates that a high degree of thermodynamic consistency is preserved across all phases. Therefore, we newly define the computational process encompassing the first-principles uncertainty revealed by this likelihood analysis as the “theoretical phase diagram calculation method.” By applying this method to the binaries and ternary of the Cu-Ni-Si system, we demonstrated its capability to reproduce experimental phase diagrams with high precision.
Suzuki et al. (Tue,) studied this question.