Realistic grand canonical Monte Carlo surface simulation: application to Ar(111)

Most realistic, off-lattice surface simulations are done canonically--- conserving particles. For some applications, however, such as studying the thermal behavior of rare gas solid surfaces, these constitute bad working conditions. Surface layer occupancies are believed to change with temperature, particularly at preroughening, and naturally call for a grand canonical approach, where particle number is controlled by a chemical potential. We report preliminary results of novel realistic grand canonical Monte Carlo simulations of the Lennard-Jones (LJ) fcc(111) surface, believed to represent a quantitative model of e.g. Ar(111). The results are successful and highly informative for temperatures up to roughly 0.8 T_m, where clear precursor signals of preroughening are found. At higher temperatures, convergence to equilibrium is hampered by large fluctuations.