Growth and structure of small gold particles on rutile TiO2(110)

The growth and structure of small Aun particles (n=1-4) on a rutile TiO2(110) surface have been examined using gradient corrected density functional theory slab calculations. We present potential energy maps for single Au atoms on the stoichiometric and reduced surfaces. This comparison shows that the presence of oxygen vacancies on TiO2(110) drastically alters the adsorption and surface diffusion of single Au atoms, and in turn the growth and structure of Au particles. On the reduced surface, the delocalization of electrons from oxygen vacancies provides a low-energy diffusion channel for Au adatoms along a Ti(5c) row, while there is no preferential direction in Au diffusion on the stoichiometric surface. The small Au particles bind preferably to the vacancy site, with a sizable adsorption energy that oscillates with the number of constituent atoms by virtue of spin pairing. Based on the comparison of supported and gas-phase Au particles, we also discuss the effect of the particle-substrate interaction on the structure of small Au particles grown on TiO2(110).