Empirical expression for the pressure-composition-temperature curve of the Zr₂Fe-deuterium system

Empirical equations for the pressure-composition-temperature (PCT) curve of the Zr₂Fe-D₂ system were developed using the relation of R_gT In(p_D2/p₀) = ΔH_s - T(ΔS_s + 2S̄_conf). The constant value of -101.8 kJ mol^-1 was given for ΔH_s regardless of the atomic ratio of D to Zr₂Fe, which is denoted as r. The ΔS_s + 2S̄_conf term was expressed by using the fourth-order polynomial of r. Although a past analytical equation could not be extrapolated to lower pressure, the present empirical equation fitted well a wide range of the PCT data. When Zr₂Fe underwent the disproportional reaction, PCT data could not be correlated by the empirical equations.