We have carried out a comparative study of phase separation and subsequent coarsening of the microstructure in a two-dimensional atomistic model system using two approaches: a stochastic Monte Carlo model and a deterministic mean field model. The differences between these approaches in the microstructural morphology, coarsening mechanisms, and kinetics are discussed. As a main result, we have found that using a realistic diffusion mechanism of vacancy motion in a Monte Carlo model produces a variety of coarsening mechanisms over a range of temperatures, which is reflected in the corresponding kinetic behavior. At low and intermediate temperatures coarsening proceeds through Brownian motion and coalescence of smaller particles, but at higher temperatures the Lifshitz-Slyozow-Wagner evaporation of smaller particles and growth of larger particles dominates. By contrast, Brownian motion of particles is not observed in a microscopic mean field model, either with or without an environment dependence in the mobility, nor is it observed within a Monte Carlo model in which diffusion is effected by direct atomic exchange (Kawasaki dynamics). The time scale associated with microscopic mean field models is discussed critically.

• Received 23 June 1998

DOI:https://doi.org/10.1103/PhysRevB.59.13681