Electronic properties of transition-metal nitrides: The group-V and group-VI nitrides VN, NbN, TaN, CrN, MoN, and WN

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Abstract
Motivated by the prediction that B1-structure MoN is a high-temperature superconductor, we present self-consistent augmented-plane-wave calculations of the electronic structure of the group-V and group-VI transition-metal nitrides VN, NbN, TaN, CrN, MoN, and WN. Comparisons of the energy bands, densities of states, and general bonding characteristics are made within this group, as well as with previously calculated transition-metal carbides. The calculated Stoner enhancement factor S for CrN indicates that the paramagnetic state is unstable with respect to ferromagnetism, consistent with the known antiferromagnetism in this compound. The calculated value of S=2.15 for MoN is not large enough to provide a serious impediment to superconductivity. The superconducting properties are evaluated within the Gaspari-Gyorffy theory for the electron-phonon coupling constant λ, calculated to be ∼1.6 in MoN (about 60% larger than in NbN). The problem of stabilizing the metastable B1 structure over the thermodynamically more stable hexagonal MoN material is considered.