Thermodynamic modeling of the Cr-Pt binary system using the cluster/site approximation coupling with first-principles energetics calculation

A thermodynamic description of Cr-Pt was developed in this study by combining first-principles calculation with the Calphad approach. The 0 K enthalpies of formation of Cr₃Pt (A15), the ordered Cr_xPt_1-x face-centered cubic (fcc) L1₂ compounds at x(Pt) = 0.25 and 0.75 and L1₀ compound at x(Pt) = 0.5 were obtained from first-principles calculation. They were used for optimizing the Gibbs energies of the corresponding phases in the Cr-Pt system. The cluster/site approximation (CSA) model was employed to model the phases in the fcc family: ordered L1₂, L1₀ and disordered A1 (they are also referred to as the three states of fcc phase). The phase boundaries and thermodynamic properties calculated from the current thermodynamic description are in good agreement with the experimental data as well as the first-principles calculation. The stability of the three fcc states and the order-disorder transition of L1₂/A1 and L1₀/A1 are reasonably described by the current description.