Heat capacities, as a function of temperature, are calculated for Ar-7, Ne-7, and Kr-7 clusters adsorbed on the basal plane of graphite using the J-walking Monte Carlo technique. The graphite surface is modeled using the Steele potential, with and without corrugation. By applying simulated annealing techniques, the minimum-energy configuration at zero kelvin is obtained. The minimum-energy configuration in the flat surface is a two-dimensional structure at a distance above the surface, identical to that determined for the rare-gas atom forming the cluster; On the Other hand, the corrugated surface yields incommensurate clusters, but which are centered in the hexagonal adsorption sites of the basal plane of graphite. The large number of high-energy isomers in the corrugated surface leads to an increase in the coexistence region when compared to the flat surface. Calculation of heat capacity as a function of temperature clearly. shows this increment.