Valleys and Hills of Graphene on Ru(0001)

The structure of graphene on Ru(0001) has been extensively studied over the last decade, yet with no general agreement. Here, we analyze graphene’s valleys and hills using a combination of X-ray standing wave (XSW) and density functional theory (DFT). The chemical specificity of XSW allows an independent analysis of valleys and hills, which, together with the DFT model, results in the precise determination of the distance between the flat, strongly bounded valleys of graphene and the substrate as well as the corrugation presented in the weakly bounded hills. From the theoretical viewpoint, the good agreement with the experiment validates the choices regarding the unit cell size and the nonlocal correlation functional.