Re-modeling of Laves phases in the Cr-Nb and Cr-Ta systems using first-principles results

Abstract

Total energies of Laves phases Cr2X, CrX2, CrCr2 and XX2 (X=Nb,Ta) in all three structural forms C14, C15 and C36 have been calculated ab initio by pseudopotential VASP code with a complete relaxation of structural parameters. The calculated values were used in a two-sublattice model for re-modeling of Gibbs energies of Laves phases and subsequently for calculation of phase diagrams of Cr-Nb and Cr-Ta systems by CALPHAD method. It turns out that application of ab initio calculated values of total energy of hypothetical "end-members" in a two-sublattice model substantially simplifies the modeling and lowers the number of necessary parameters. Comparison of phase diagrams obtained by a model using first-principles results with previous empirical approach as well as relative stability of Cr2X polytypes is presented. © 2008 Elsevier Ltd. All rights reserved.