Homogeneous nucleation under shear in a two-dimensional Ising model: Cluster growth, coalescence, and breakup

We compute rates and pathways for nucleation in a sheared two-dimensional Ising model with Metropolis spin flip dynamics using forward flux sampling (FFS). We find a peak in the nucleation rate at intermediate shear rate. We analyze the origin of this peak using modified shear algorithms and committor analysis. We find that the peak arises from an interplay between three shear-mediated effects: Shear-enhanced cluster growth, cluster coalescence, and cluster breakup. Our results show that complex nucleation behavior can be found even in a simple driven model system. This work also demonstrates the use of FFS for simulating rare events, including nucleation, in nonequilibrium systems. (C) 2008 American Institute of Physics.