Relative Partial Molar Gibbs Energy of Magnesium Component Substituted into Zinc Site in the Mg-Zn Binary Compounds

Abstract

Relative partial molar Gibbs energies of the Mg component substituted into the Zn site, Δ\\barG_Mg^{Mg on Zn site}, in the intermediate phases of Mg_0.48Zn_0.52 and Mg_0.4Zn_0.6 in the Mg-Zn binary system were directly evaluated, assuming that change in the chemical potential of magnesium, Δμ_Mg, as a function of the composition in a narrow solubility limit is caused by anti-site substitution of Mg atoms at the Zn site. At 298 K, the Δ\\barG_Mg^{Mg on Zn site} values of Mg_0.4Zn_0.6 and Mg_0.48Zn_0.52 were found to be 1.254 and 0.163 MJ·mol⁻¹, respectively, consistent with about the same order of internal energy of the Fe components substituted into the Pt site, ΔU_Fe^{Fe on Pt site}, in the ordered phase of L1₀-Fe_1−xPt_x calculated by theoretical calculation (=0.101 MJ·mol⁻¹). When the symmetric atomic configuration at the stoichiometric composition was violated by anti-site substitution, the relative partial molar thermodynamic value of lattice defect was found to be very large.