Phase transitions at the early stages of surface melting

We show that the early stage of surface melting can be associated with a we ll defined phase transition, of the pre-roughening type. The problem is mod eled by simulating the surface as an interface in the three-dimensional lar ge N-state lattice Potts model, which is shown to exhibit pre-roughening, r oughening, and a lattice version of surface melting. The lowest transition is pre-roughening, but it is in fact linked to the appearance of liquid-lik e signatures in the first surface layer, and thus represents the phase tran sition where surface melting starts. We suggest that this physics is realiz ed on rare-gas-solid (111) surfaces and possibly also on other semiconducto r and metal surfaces. (C) 2000 Published by Elsevier Science B.V. All right s reserved.