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The phase diagram of the first layer of 4He adsorbed on a single graphene sheet has been calculated by a series of diffusion Monte Carlo calculations including corrugation effects. Since the number of C-He interactions is smaller than in graphite, the binding energy of 4He atoms to graphene is reduced approximately 13.4 K per helium atom. Our results indicate that the phase diagram is qualitatively similar to that of helium on top of graphite. A two-dimensional liquid film on graphene is predicted to be metastable with respect to the commensurate solid but the difference in energy between both phases is very small, opening the possibility of such a liquid film to be experimentally observed.

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We carried out molecular dynamics simulations to describe the properties of water inside a narrow graphite channel. Two stable phases were found: a low-density one made of water clusters adsorbed on the graphite sheets and a liquid one that fills the entire channel, forming several layers around a bulk-like region. We analyzed the interfacial structure, orientational order, water residence times in several regions, and hydrogen bonding of this last water phase, calculating also a quantity of electrochemical interest, the probability of electron tunneling through interfacial water. The results are in good qualitative agreement with the available experimental data.