Numerical evaluation of the exact phase diagram of an empirical Hamiltonian: Embedded atom model for the Au-Ni system

Molecular-dynamics simulations were used to calculate the Gibbs free energy on the entire compositional range of gold-nickel alloys described with a set of embedded atom potentials available in the literature. Thermodynamic integration and switching Hamiltonian techniques were used to obtain the exact phase diagram (with no approximations), and that corresponding to the regular approximation. Remarkable agreement for some properties, such as the solvus critical point, the congruential melting, the melting points of the pure elements, and the formation entropy of the alloy, contrasts with the poor prediction of the location of the solidus-liquidus lines, reflecting errors in the heat of solution in the liquid phase. The results are compared with recent experimental reassessment of the Au-Ni phase diagram and with ab initio calculations.