Periodicity, work function and reactivity of graphene on Ru(0001) from first principles

Using density functional theory (DFT), a detailed analysis of the energetic and electronic properties of monolayer graphene on Ru(0001) was performed. Firstly, we demonstrate that the corrugated (12 x 12)C/(11 x 11) Ru structure is an absolute minimum among smaller and larger commensurabilities. Secondly, we show that the reduced work function originates from the charge depletion in the graphene skeleton states at bonded carbon atoms, in contrast to the assumed n-doping of pi states. We further propose that the higher-lying regions of the graphene layer form an array of electronically disconnected nanographene islands. Finally, we explore the adsorption properties of this template with respect to metals by comparing the adsorption of Au and Pt single atoms. A 1.1 eV (0.7 eV) preference is found for Au (Pt) atop adsorption in the low region with 0.2-0.3 eV selectivity for the (hcp, top) locations, in agreement with recent experiments on Pt clusters.