First-principles study of Au nanostructures on rutile TiO2(110)

We report systematic density-functional theory calculations of the structure and energetics of Au-n nanorows (n=1-7) and clusters (n=1-12) adsorbed on the defected (110) rutile surface. The calculations show that gold nanorows bind strongly to a missing-row defected TiO2 surface with an adhesive binding energy of about 1.5 eV. The cohesive binding energy of Au atoms in a row amounts to about 2.5 eV/atom. An analysis of the gold row properties points to their metallic nature. The charge redistribution on adsorbed rows shows that all Au-n rows are negatively charged compared to the free-standing structures. The adhesive bonding of gold clusters to the vacancy defected bridging oxygen row at the TiO2(110) is of covalent nature and is stronger than that of the Au rows. The cohesive energy per atom in a Au-n cluster is about 2.2 eV for the n >= 5 clusters and is larger (similar to 2.3-2.4 eV) for smaller ones. We found that all clusters studied are negatively charged with about 1.1 electron charge. This charging shows only a weak dependence on the odd-even number of gold atoms forming a cluster.