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 onsurface 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.