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

Abstract

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 Cr 3Ir ( A 15 ), ε (hcp), and ordered Cr x Ir 1− x face-centered cubic (fcc) compounds ( L 1 2 at x ( Ir ) = 0.25 and 0.75 and L 1 0 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 L 1 2 , L 1 0 and disordered A 1 . 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.