  The alloying effect on the lattice parameters, isostructural mixing
enthalpies and ductility of the ternary nitride systems Cr1-xTMxN (TM=Sc, Y;
Ti, Zr, Hf; V, Nb, Ta; Mo, W) in the cubic B1 structure has been investigated
using first-principles calculations. Maximum mixing enthalpy due to large
lattice mismatch in Cr1-xYxN solid solution shows a strong preference for phase
separation, while Cr1-xTaxN exhibits a negative mixing enthalpy in the whole
compositional range with respect to cubic B1 structured CrN and TaN, thus being
unlikely to decompose spinodally. The near-to-zero mixing enthalpies of
Cr1-xScxN and Cr1-xVxN are ascribed to the mutually counteracted electronic and
lattice mismatch effects. Additions of small amounts of V, Nb, Ta, Mo or W into
CrN coatings increase its ductility.
