3D Monte Carlo simulations of diffusion limited cluster aggregation up to the sol-gel transition: Structure and kinetics

Three-dimensional (3D) Monte Carlo simulations of diffusion limited cluster aggregation at different concentrations (phi) show a crossover from a flocculation regime at short times to a percolation regime close to the gel time (t(g)). Contrary to suggestions in the literature t(g) is independent of the system size (L) for large L. The structural and temporal crossovers between flocculation and percolation take place at characteristic values of the cluster mass (m(c)) and the time (t(c)) which depend on phi. After normalisation by these characteristic values the crossovers are independent of phi except for very small clusters and at short times. The concentration dependence of m(c) and t(c) indicates that the crossover takes place at a given cumulated volume fraction of the clusters independent of phi. At low concentrations the phi-dependence of t(g) is determined by the cluster growth in the flocculation regime.