Preroughening and Reentrant Layering Transitions on Triangular Lattice Substrates

Recent ellipsometric and calorimetric studies of argon and krypton adsorbed on triangular lattice graphite substrates have found a novel sequence of apparent reentrant layering transitions between integer-plus-one-half coverages. Related behavior has been demonstrated in a Monte Carlo study by Phillips, Zhang, and Larese. In contrast to arguments made by these authors, however, we use solid-on-solid models that include a substrate potential to demonstrate that this behavior should be expected to arise out of the physics that produces roughening and preroughening of a bulk crystal surface, which then provides a unified picture of both the experiments and the simulation results.