Citation:
Lev D. Gelb, Molecular Physics 88 #6 (1996) 1541-1561

Abstract: We have developed a lattice model in the mean-field approximation in order to study the surface phase behaviour of the Lennard-Jones system. This model reproduces the phase diagram of Lennard-Jones atoms to reasonable accuracy. We have studied the effects of all of the inherent approximations in the model, and performed many supplementary calculations to determine the sensitivity of the bulk and surface phase diagrams to these approximations. We have investigated the phenomenon of surface melting using this model, and found that the three different crystal faces we consider all exhibit different degrees of layering behavior at the onset of surface melting. A more careful analysis indicates that this behavior is due to a perturbation caused by the reference lattice. Although a very similar model has been used to study the same system by A. Trayanov and E. Tosatti (1988, Phys. Rev. B, 38, 6961), much of this behaviour went unobserved. We have determined that this is due to their observing a melting point that is too high, which obscures this behaviour. We have also resolved some technical difficulties which they experienced in their study of the (111) face of the Lennard-Jones crystal. Based on these data we argue that the Lennard-Jones crystal only surface melts incompletely.