計算状態図と材料設計への展開 新規熱力学平衡計算ソフトウェア（ＣａＴＣａｌｃ）の開発

Abstract

Thermodynamic equilibrium calculation is sometimes difficult in a system when minor but important species are present, when only stoichiometric condensed phases are stable and the gas phase is absent, and when multiple minima are present in the Gibbs free energy of some non-ideal solution phases. New program is being developed to overcome these problems. The free-energy minimization method is implemented to determine thermodynamic equilibrium similarly to other conventional programs. However, the gas phase in equilibrium is assumed to be present even when the gas phase is unstable under the specified condition, similar to the equilibrium constant method. Chemical potentials of the system components are always determined uniquely by this additional condition, and the vapor pressure and composition can be calculated. Furthermore, an automatic routine that introduces multiple phases with different compositions and checks their stability is incorporated to detect possible phase-splitting in non-ideal solution phases.