Comparison of thermodynamic properties of cubic Cr1-x Alx N and Ti1-x Alx N from first-principles calculations

In order to investigate the stability of the cubic phase of Cr 1−x Al x N at high AlN content, first principles calculations of magnetic properties, lattice parameters, electronic structure, and mixing enthalpies of the system were performed. The mixing enthalpy was calculated on a fine concentration mesh to make possible the accurate determination of its second concentration derivative. The results are compared to calculations performed for the related compound Ti 1−x Al x N and with experiments. The mixing enthalpy is discussed in the context of isostructural spinodal decomposition. It is shown that the magnetism is the key to understand the difference between the Cr-and Ti-containing systems. Cr 1−x Al x N turns out to be more stable against spinodal decomposition than Ti 1−x Al x N, especially for AlN-rich samples which are of interest in cutting tools applications.