Combined ab-initio and experimental assessment of A1−xBxC mixed carbides

The excess energies for A1−xBxC mixed carbides (where A and B are metals) have been calculated using ab-initio calculations, for 14 systems. A thorough comparison has been made with experimentally assessed excess energies. The comparison shows that conventional ab-initio calculations applied to rather simple structural models can be used to predict the sign, magnitude and symmetry of the excess energy for A1−xBxC mixed carbides. The calculated excess energies have also successfully been used to describe several AC–BC systems where the experimental information does not give a unique determination of the excess energy in traditional CALPHAD modelling. The systems that have been studied are CrC–TiC, HfC–NbC, HfC–TaC, HfC–TiC, HfC–VC, NbC–TaC, NbC–VC, NbC–ZrC, TaC–VC, TaC–ZrC, TiC–VC, TiC–ZrC and VC–ZrC.