| The first three-dimensional Brownian dynamics simulations of concentrated colloidal suspensions, modeling the disorder/order transition in polymerically stabilized systems, are analyzed. The mechanisms of the transition are explored as a function of volume fraction and interparticle potential, for both a steeply repulsive potential and for one containing an additional attractive tail. The simulation includes not only the interparticle forces, but also Brownian motion and viscous forces due to the interstitial fluid, treated as a continuum. The simplest hydrodynamics, neglecting interactions, are utilized.; The full range of behavior (from liquid, to partially-crystalline solid, to glass) is observed as volume fraction increases, in agreement with experimental studies and atomic simulations of the transition. The relaxation from a metastable, disordered state toward an ordered one is manifested in steep changes in system properties, in particular, the particle mean-squared displacement, the osmotic compressibility factor, and the radial distribution function. The qualitative aspects of the relaxation agree with those observed in simulations of atomic systems. The purely repulsive potential gives rise to more dramatic changes in system properties and a greater tendency toward glass formation.; The Voronoi polyhedra analysis, applied here for the first time to colloidal systems, reveals an increase in the number of particles in crystalline environments as the system properties listed above relax. Quantitative measures of the critical nucleus size and the time for onset of nucleation agree with those found in simulations of atomic systems, when appropriately scaled. The rate of growth of the nuclei coincides with that observed experimentally for crystallization in electrostatically stabilized suspensions. In addition, characterization of the nuclei indicates a fractal dimension comparable to that for aggregate formation. |
