Based on all-electron self-consistent fully relativistic Korringa-Kohn-Rostoker coherent potential approximation results, concentration- and lattice-parameter-dependent effective pair interactions up to the fifth nearest neighbors are calculated in terms of the fully relativistic embedded cluster method for the Au-Pd system. The obtained effective pair interactions are then used to evaluate a simplified (${\mathit{V}}_{1}$,${\mathit{V}}_{2}$) phase diagram, ordering energies, and related quantities.