In this work, interaction energies between pairs of atoms for the Ag-Pb, Cu-Pb and Sn-Pb systems have been calculated using ab initio methods. These energies are then used as the interaction energy parameters in the Wilson equation. Phase diagram of vapor-liquid equilibria (VLE) for the Pb-based alloy systems in vacuum distillation are obtained based on the calculated parameters. The results indicate that this approach can lead to accurate VLE predictions for alloy systems in vacuum distillation based only on properties of pure components and the structure of the clusters. The comparisons show the computational results are in good agreement with the experimental data. (C) 2016 Elsevier B.V. All rights reserved.