Vacancies, interstitials and their complexes in titanium carbide

Titanium carbide is a prototype transition-metal compound and is used in various applications due to its exceptional hardness and stability. Here we use first-principles calculations to elucidate the properties and interactions of TiC point defects and their role on the thermal stability of TiC films. We find that the stability of defects and defect complexes depends strongly on structural details. We also show via calculations of diffusion barriers that, while carbon interstitials are relatively mobile species, the migration of carbon vacancies is suppressed unless the sample is heated to extremely high temperatures. We close with a discussion on defect-related effects and a comparison with similar physical traits in transition-metal nitrides. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.