Reaction coordinates for the crystal nucleation of colloidal suspensions extracted from the reweighted path ensemble.

We study the mechanisms of the homogeneous crystal nucleation from the supercooled liquid to the crystal phase in the Gaussian core model for colloidal suspensions with the aim to find optimal reaction coordinates. We introduce a set of novel collective variables based on the local structure of particles. By applying likelihood maximization of the committor function for the reweighted path ensemble constructed by replica exchange transition interface sampling, we select the optimal reaction coordinates from the set of collective variables. We find that the size of the cloud of prestructured particles surrounding the crystalline nucleus enhances the description of the transition. Further, we show that the rearrangement of the inner core of the nucleus according to Ostwald's step rule is a separate process, independent of the growth of the nucleus.