First-principles calculations were used to study the effect of vacancies on the structural and electronic properties in sub-stoichiometric TiCx. The effect of vacancies upon the equilibrium volumes, bulk moduli, electronic band structures and density of states of the sub-stoichiometric phase was studied by using a full-potential linear augmented plane-wave method. A model structure of 8-atom super-cells with ordered vacancies within the C sub-lattice was used. It was found that the lattice parameters of the studied stoichiometries were smaller than that of ideal stoichiometric TiC. The results for the variation of the lattice parameters and the bulk moduli for TiCx were found to be in good agreement with experiment. The results were compared with a recent full-potential calculation involving relaxed 16-atom super-cells.

First-Principles Calculations of Vacancy Effects on Structural and Electronic Properties of TiCx and TiNx. Z.Dridi, B.Bouhafs, P.Ruterana, H.Aourag: Journal of Physics - Condensed Matter, 2002, 14[43], 10237-49