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 (∼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.