Application of MIVM for phase equilibrium of Sn–Pb–Sb system in vacuum distillation

• Based on the MIVM, we calculated activities of components of Sn–Pb–Sb alloy.
• The phase equilibrium of Sn–Pb–Sb alloy in vacuum distillation were predicted.
• It can be used to choose the processing conditions and needed products.
• The content of tin in vapor phase decreases when Sb was added into the Pb–Sn system.

Based on the molecular interaction volume model (MIVM), the pair-potential energy parameters Bji and Bij of the related binary Sn–Pb, Pb–Sb and Sn–Sb alloy systems were calculated using the infinite dilution activity coefficients γi∞ and γj∞. The activities of components of the Sn–Pb–Sb ternary alloy system were predicted using Bji and Bij. Finally, the vapor–liquid phase equilibrium of the Sn–Pb–Sb alloy system was predicted using only the properties of pure components and the activity coefficients, which indicates that Sn can be separated from Pb and Sb by vacuum distillation thoroughly. A significant advantage of the model lies in its ability to predict the thermodynamic properties of multi-component liquid alloys using only two parameters. Moreover, the MIVM is reliable due to it has certain physical meaning from the viewpoint of statistical thermodynamics.