Transitions of gases physisorbed on graphene

The behavior of gases physically adsorbed on graphene might be expected to be similar to that of ones adsorbed on graphite. Here, three kinds of phase transitions are examined for gases adsorbed on suspended, free-standing graphene. In one case, the quasi-two-dimensional condensation of a van der Waals fluid is evaluated, using perturbation theory. In a second case, changes are discussed for contributions to the ground state energies of monolayer solid and liquid phases of quantum adsorbates (especially He) on graphene. This includes a determination of the leading perturbation terms in the adsorption-mediated (McLachlan) dispersion energy for two adatoms on a graphene sheet. The third problem is the wetting transition of water and other fluids on graphene. In each case, the relevant energies are somewhat different from those for adsorption on graphite.