Computational assessment of Sn activities and integral excess free energy change for mixing in the Sn-Au-Cu ternary liquid alloys using the molecular interaction volume model

The activities of Sn in the liquid solder ternary alloy Sn-Au-Cu at 900 K have been computed using the molecular interaction volume model (MIVM). The calculated values have been compared with the experimental data for three cross-sections, i.e., for three different ratios of aurum to copper (XAu:XCu) = 3:1, 1:1, and 1:3. In addition, the excess Gibbs free energy of mixing, Delta GEx, for these ternary liquid alloys has been determined using the same model parameters to assess their validity. The resulting values have then been compared with the corresponding experimental data found in the literature. The agreement between the theoretical and experimental results has been found to be satisfactory.