Prediction of site preference and phase stability of transition metal based frank-kasper phases

Site preference of transition metals for crystal sites in Frank-Kasper type tetrahedrally close packed phases has been computed using density functional based electronic structure methods and cluster expansions. Comparisons with results from X-ray and neutron scattering experiments, where available, indicate that theoretical results are accurate. The cluster expansion method is used to analyze whether site preference is driven by onsite effects (such as atomic size) or chemical ordering effects (such as maximization of unlike bonds). Moreover the role of vibrational degrees of freedom on the site preference is discussed.