Diffusion of Ti through the TiO2(110) rutile surface plays a key role in the growth and reactivity of TiO2. To understand the fundamental aspects of this important process, an analysis was made of the diffusion of Ti ad-species at the stoichiometric TiO2(110) surface using complementary computational methodologies of density functional theory corrected for on-site Coulomb interactions (DFT + U) and a charge equilibration (QEq) atomistic potential to identify minimum energy pathways. It was found that diffusion of Ti from the surface to sub-surface (and vice versa) follows an interstitialcy exchange mechanism, involving exchange of surface Ti with the 6-fold coordinated Ti below the bridging oxygen rows. Diffusion in the sub-surface between layers also follows an interstitialcy mechanism. The diffusion of Ti was discussed in light of continued attempts to understand the re-oxidation of non-stoichiometric TiO2(110) surfaces.

Surface and Interstitial Ti Diffusion at the Rutile TiO2(110) Surface. Mulheran, P.A., Nolan, M., Browne, C.S., Basham, M., Sanville, E., Bennett, R.A.: Physical Chemistry Chemical Physics, 2010, 12[33], 9763-71