Semi-empirical equations for pressure-composition-temperature curves of the Ti-H system

Semi-empirical equations were developed for the pressure-composition-temperature (PCT) curves of the α, β, δ and ε{lunate} phases in the TiH system. Past PCT data were correlated within a practical accuracy using a difference in the excess chemical potential of hydrogen in Ti. The excess chemical potential difference in the α phase was calculated based on the ideal one-site model. The excess chemical potential difference in the β phase was evaluated by assuming that the partial molar enthalpy and entropy increase linearly with hydrogen content and for that in the δ and ε{lunate} phases by assuming that the partial molar enthalpy is constant.