The structural energetics and diffusion mechanisms of the most important point defects in rutile, the O vacancy (VO) and the Ti interstitial (Tii), were studied using ab initio pseudopotential total-energy methods. The defects were found to be competitive in energy; with VO being more favorable over a larger range of the stoichiometry. On the other hand, Tii was shown to be the major diffusive species since its migration barrier was significantly smaller (by ~1eV) when compared with that of VO. The diffusion mechanisms of Tii, parallel and perpendicular to the c-axis, were found to be different; with a surprisingly larger barrier along the more-open [001] direction (originally thought to be the easier channel for Ti self-diffusion). These theoretical findings were in excellent quantitative agreement with existing experimental data.

Diffusion Mechanisms of Native Point Defects in Rutile TiO2 - ab initio Total-Energy Calculations. H.Iddir, S.Öğüt, P.Zapol, N.D.Browning: Physical Review B, 2007, 75[7], 073203 (4pp)