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 dynamics 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 strong surface-induced structural fluctuations at the close packed 100 surface. Away from equilibrium we find (i) the surfaces exhibit identical 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 melting, double that seen in freezing; and (iv) over a range of small supercoolings (less than 0.5% of the melting temperature) the interfacial velocity vanishes. The 111 surface is found to exhibit microfacets of 100 orientation over the entire temperature range studied. The asymmetry between freezing and melting dynamics and the origin of the stationary surface at small supercoolings are discussed in terms of the role of symmetry breaking fluctuations on the dynamics of interface motion.