Adsorption and cluster growth of vanadium on TiO2(110) studied by density functional theory

A first-principles study on adsorption, diffusion, and cluster growth of vanadium on TiO2(110) is presented. We find that the most stable adsorption site of a single V atom is the "upper hollow site" in agreement with recent experiments. However several subsurface sites involving Ti-substitution are more stable than any on-surface adsorption site. Major diffusion channels have been determined. The lowest energy diffusion barrier (0.7 eV) is that between the most stable adsorption site and the most stable Ti-substitutional site. The interaction between two neighboring V adatoms is repulsive. Surface clusters are stable from three V atoms on. The most stable five and eight atom clusters are pyramidal chains along [001] with a body centered cubic coordination. For a coverage below about 0.3 monolayer, V preferentially occupies subsurface sites. For higher coverage, it forms clusters on the surface.