Onset of the crystalline phase in small assemblies of colloidal particles

We report the findings of a computational study designed to determine the onset of a stable crystalline phase in assemblies of small numbers (13-32) of colloidal particles that interact via a depletion-based short-ranged attractive potential. Using Monte Carlo umbrella sampling with coarse graining in two order parameters, we generate free-energy landscapes that can indicate coexistence between fluid-like and crystalline phases. The emergence of a stable crystalline phase is observed as the number of particles in the assembly increases beyond a critical value. We find that the critical cluster size for crystallization onset decreases with increasing strength of the interparticle attraction.