On the electronic structure of TiNx

The electronic structure of substoichiometric TiN x is studied in terms of the KKR GF and KKR CPA methods. In accordance with recent XPS studies the cases of both a single vacancy and concentrated vacancies show peaks in the vicinity of the minimum in the density of states of the stoichiometric compound. The nature of the 'vacancy sub-band' is analysed in detail in terms of the resonance condition for virtual bound states. The Fermi energy for TiN x , x=0.75, is lower than in the stoichiometric case, the density of states at E F being about 10% higher in the non-stoichiometric system than in the pure system. It is argued that the results obtained are also characteristic of other substoichiometric refractory carbides and nitrides.