The influence of structural vacancies in metal and non-metal sub-lattices on the electronic structure of titanium carbide and oxide was studied by the non-empirical Hartree-Fock-Slater method in the cluster approximation. The main valence band changes for non-stoichiometric compounds were connected with the narrowing of bands due to subtraction of a number of electronic states and an increase of density of states near the Fermi level. Vacancy states appeared to be localized in the unoccupied region of the energy spectrum; their admixture in the valence band was very small. The valency of metal atoms was shown to vary continuously in accordance with the stoichiometry ratio. The vacancy charge was very much smaller than the formal ionicity of the atom removed. It was shown that in defect compounds there was essentially no bonding charge connected with the vacancy center.

Vacancies and the Energy Spectrum of Refractory Metal Compounds: TiC and TiO. Gubanov, V.A., Ivanovsky, A.L., Shveikin, G.P., Ellis, D.E.: Journal of Physics and Chemistry of Solids, 1984, 45[7], 719-30