First-principles study of the adsorption of Au atoms and Au-2 and Au-4 clusters on FeO/Pt(111)

Adsorption of Au atoms and Au-2 and Au-4 clusters on Pt(111)-supported bilayer FeO film were studied using first-principles density functional theory. For atom adsorption on the FeO/Pt(111) coincidence lattice, two types of adsorption were found, in agreement with previous studies. One is that the Au atom binds with one Fe cation lifted from underneath to the top of the oxygen layer (flipped adsorption), and the other is that the Au atom adsorbs directly on the oxygen layer (direct adsorption). Flipped adsorption was found to be energetically most favored in all domains of the Moire superstructure, while direct adsorption was either metastable or unstable. The charge of the Au adatom is negative for the flipped adsorption and positive for the direct adsorption. For the Au2 and Au4 clusters, the global most stable adsorption configurations on the FeO/Pt(111) were explored, and the results indicated that one-dimensional (dimer) or two-dimensional (Au-4) upright configurations of direct adsorption were energetically preferred over the flat or three-dimensional ones throughout the Moire superstructure. Moreover, it was found that the configurations of Au-2 dimers and Au-4 clusters on FeO/Pt(111) is tightly related to the interfacial interaction including two effects: the direction-dependent reactivity of a planar Au cluster and the interfacial electrostatic interaction between the Au clusters and the FeO/Pt(111) support. The role of relativistic effects in the configuration of Au clusters and the interaction with FeO/Pt(111) were illustrated. The evolution of small Au cluster configuration on FeO/Pt(111) was discussed