Electronic structure of substoichiometric carbides and nitrides of zirconium and niobium

The electronic structures of ZrCₓ, ZrNₓ, NbCₓ, and NbNₓ for several concentrations x were investigated by means of the Korringa-Kohn-Rostoker coherent-potential approximation and the Korringa-Kohn-Rostoker Green's-function methods. The influence of vacancies on the electronic structure of these compounds is quite similar to the case of substoichiometric carbides and nitrides of 3d metals: near the minimum in the density of states between the nonmetal p and the metal d subbands additional ``vacancy peaks'' appear, and (except for ZrCₓ) the Fermi energy is lowered. It is argued that similar properties may be expected for other d- and f-metal carbides, pnictides, and chalcogenides.