Development of the ReaxFF Reactive Force-Field Description of Gold Oxides

For the investigation of the interaction between oxygen and gold over length-and time-scales which reflect the operation of real catalysts, the reactive force-field (ReaxFF) description of the O/Au interaction has been developed. This development has been achieved in two stages: first, by fitting the parameters of the potential against an extensive set of both bulk and surface Au, O-2, and gold oxides derived from full quantum mechanical simulations. The resulting potential has been used in a series of molecular dynamics (MD) simulations emulating the interaction between oxygen and the Au(111), the missing-row (1 x 2)-mr-Au(110), pairing-row (1 x 3)-pr-Au(110), trenched (1 X 3)-tr-Au(110), and added-row (2 X 1)-ar-Au(100) surfaces. These simulations have shown, in agreement with experimental studies, that oxygen diffusion from the surface to the bulk is heavily limited and generally only possible when thermal processing has started melting the Au substrate. Grand canonical Monte Carlo/molecular dynamics (GC-MC/MD) simulations of Au nanoclusters have shown that the (111) and (100) facets of these particles are unreactive toward oxygen.