Theoretical Study of Adsorption of Ag Clusters on the Anatase TiO2(100) Surface

The adsorption of silver atoms, dimers, tetramers, and octamers on the perfect anatase (100) surface has been studied theoretically at density functional theory level. Two complementary approaches based on linear combinations of atom-centered Gaussian-type basis functions and plane waves were applied. The most preferable adsorption positions were found to be hollow sites between two-coordinated oxygen atoms (O(2c)). Adsorption on the Ti-O planes is energetically less favorable. The binding mechanism was interpreted in terms of the interaction between cluster orbitals and orbitals of O(2c) atoms. The charge transfer leads to a deformation of the cluster shape compared with the stable gas-phase structures. In the Ti-O plane sites, an additional binding mechanism exists through the overlap between the silver cluster's HOMO and unoccupied orbitals of five-coordinated titanium atoms. The same bonding mechanisms have been found previously for the adsorption of Ag particles on the rutile (110) surface(1). The growth of silver clusters on the anatase (100) surface via aggregation is an exothermic process and leads to the formation of three-dimensional structures.