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A system of nearest-neighbor interacting spins driven by a Glauber-type dynamics on a two-dimensional hexagonal lattice was studied as a model for a first order phase transition. The primary goal of the study was to verify the kinetic aspects of the conventional nucleation and growth description which is associated with the motion of the interface, the growth and decay of individual nuclei, and with their size distributions. The role of time-dependent nucleation was highlighted, and the overall kinetics of the phase transition were examined. By an artificial modification of the dynamics in order to exclude some of the paths in the formation or destruction of nuclei, coagulation effects were studied. The latter have only minor influence in the immediate vicinity of the binodal, but increase rapidly upon intrusion into the metastable phase. ͓S0163-1829͑99͒02305-X͔

Large-scale dynamic Monte Carlo simulations of a lattice gas on a 2000×2000 square lattice with a Glauber-type spin flip dynamics were performed. The results are discussed in the light of classical nucleation theory (CNT) which can be fully specified for the problem due to the availability of exact values for the interfacial energy of a large nucleus, known from the Onsager solution. Several alternative (field-theoretic or nonclassical) descriptions were also considered. Special attention was paid to the pre-exponential in the cluster distribution function and to the finite-size corrections to the interfacial energies which are required in order to comply with observations. If taken literally, the CNT produces large errors when predicting either the cluster distribution function or the nucleation rate. However, at intermediate temperatures (up to 0.7 Tc) the correspondence can be substantially improved by considering the low-temperature properties of small clusters and adjusting the pre-exponential. At higher temperatures the CNT is in qualitative disagreement with the simulations. Several explanations for this, including coagulation between clusters, are proposed.

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