Thermodynamic modeling of the Cr–Ir binary system using the cluster/site approximation (CSA) coupling with first-principles energetic calculation

A thermodynamic description of Cr–Ir was developed in this study by combining first-principles calculation with the Calphad approach. The zero-kelvin enthalpies of formation of Cr3Ir (A15A15), εε (hcp), and ordered CrxIr1−x face-centered cubic (fcc) compounds (L12L12 at x(Ir)=0.25 and 0.75 and L10L10 at x(Ir)=0.5) were obtained from first-principles calculation. They were used as initial values for optimizing the Gibbs energies of the corresponding phases in the Cr–Ir system. The cluster/site approximation (CSA) model was employed to describe the fcc family phases of three different states: the ordered L12L12, L10L10 and disordered A1A1. The phase boundaries and thermodynamic properties calculated from the current thermodynamic description are in good agreement with the experimental data available in the literature as well as the first-principles calculation in the current study.