DYNAMIC MONTE-CARLO SIMULATIONS OF FREEZING AND MELTING AT THE 100 AND 111 SURFACES OF THE SIMPLE CUBIC PHASE IN THE FACE-CENTERED-CUBIC LATTICE-GAS

Dynamic Monte Carlo simulations are used to study the structure and dy namics of the 100 and the 111 crystal-liquid interfaces of the simple cubic phase in the face-centered-cubic lattice gas. At equilibrium the two surfaces are found to be distinguished only by the presence of st rong surface-induced structural fluctuations at the close packed 100 s urface. Away from equilibrium we find (i) the surfaces exhibit identic al velocity vs temperature curves; (ii) the interfacial velocity is a Linear function of temperature (except at small supercoolings); (iii) the slope of velocity vs temperature in these linear regions is, for m elting, double that seen in freezing; and (iv) over a range of small s upercoolings (less than 0.5% of the melting temperature) the interfaci al velocity vanishes. The 111 surface is found to exhibit microfacets of 100 orientation over the entire temperature range studied. The asym metry between freezing and melting dynamics and the origin of the stat ionary surface at small supercoolings are discussed in terms of the ro le of symmetry breaking fluctuations on the dynamics of interface moti on.