Cr-Re Ab initio and thermodynamic study

Abstract

In this work the assessment of the Cr–Re system, using a combined ab initio and CALPHAD (CALculation of Phase Diagrams) approach, is presented. To model the sigma phase, a five-sublattice combined CEF model was applied and the present description reproduces reasonably well the previously published experimental phase diagram. Formation enthalpies of the stable/metastable configurations of the sigma phase were estimated from ab initio calculations. A comparison of results using simplified two- and three-sublattice models and the five-sublattice model for the sigma phase is also presented, which highlights differences in calculated properties as site occupancies. According to present outcomes, the five-sublattice model (Cr,Re)2(Cr,Re)4(Cr,Re)8(Cr,Re)8(Cr,Re)8, based on Wyckoff positions, is necessary to reproduce the atomic ordering in the sigma phase. Certain areas of the phase diagram still remain uncertain and deserve further experimental investigation.