Stability of Laves phases in the Cr–Zr system

The total energies of Laves phases with various occupations of inequivalent lattice sites in all three structural forms C14, C15 and C36 have been calculated ab initio by a pseudopotential VASP code with a complete relaxation of all structural parameters. The relative stability of Cr2Zr polytypes is discussed. The calculated values were used in two-sublattice and three-sublattice models for the re-modeling of Gibbs energies of Laves phases and subsequently for the calculation of phase diagram of the Cr–Zr system by the CALPHAD method. A comparison of phase diagrams obtained by our model using first-principles results with previous treatments using an empirical approach as well as with experimental phase equilibrium data is presented. An application of the structural energy differences (lattice stabilities) calculated ab initio provides a similarly good description of the phase diagram of the Cr–Zr system as previous studies, but much fewer adjustable parameters are needed for a thermodynamic description of Laves phases.