  A metastable phase of NbN with superconducting Tc=16.4 K was reported
recently by Treece and collaborators. The reported structure of the thin film
sample deviates from the rocksalt (B1) NbN structure with 25% ordered vacancies
on each sublattice (space group Pm3m) and a lattice constant of 4.442
Angstroms. Using full potential electronic structure methods, we contrast the
electronic structure with that of B1 NbN. The calculated energy, 1.00
eV/molecule higher than B1 NbN, and calculated lattice constant of 4.214
Angstroms indicate that the new phase must be something other than the ordered
stoichiometric Pm3m phase.
