Effect of surface roughness on the static and dynamic properties of water adsorbed on graphene

We studied the effects that deviations from a perfectly flat structure have in the adsorption of water on a single graphene sheet at room temperature. To do so we performed molecular dynamics simulations of water on top of a single sheet of carbon atoms whose positions were changed periodically or randomly and the results compared with those obtained for an ideal flat surface. Different textures were considered, and in all cases, the corresponding geometries of the single graphene layers were kept frozen through the simulations. Our results indicate that the effect of the roughness in the water molecules depends basically on the average amplitude of the distortions in the Z direction and not of their particular type (random or periodic). Binding energies and water structure are scarcely affected by corrugation, with an average number of 3.5-3 hydrogen bonds per molecule through the distance perpendicular to the surface. Analysis of water translational diffusion and spectroscopical densities of states indicates changes when water is close to the vacuum interface and far from the graphene surface.