Simulation of homogeneous crystal nucleation close to coexistence

We discuss a numerical scheme to study homogeneous crystal nucleation. Using this approach, it is possible to compute the height of the free energy barrier that separates the solid from the liquid phase and the rate at which this barrier is crossed. We point out that there is a fundamental difference between the use of a global- and a local-order parameter to measure the degree of crystallinity. Using a global-order parameter, precritical nuclei may break up spontaneously for entropic reasons. Near the top of the barrier the nuclei combine to form a relatively large cluster. The transition from many small clusters to one large cluster is discussed in some detail. Finally we present a new method that allows us to avoid this entropic cluster break up.