Abstract: Colloidal aggregation within the context of long range van der Waals forces was studied by computer simulations. The motion of colloidal particles or clusters was guided by the long range van der Waals forces. Compared to the diffusion limited cluster aggregation (DLCA), which takes no account of the guiding effect, the directionalism of van der Waals forces not only accelerates the aggregation velocity but also results in morphologies of clusters with higher density and higher fractal dimensions. The directionalism arising from long range van der Waals forces was very sensitive to the initial concentration of particles. Whether on the morphology or on the aggregating velocity, the directionalism was distinct only at low initial concentration of particles. The possible reason was that, at a high particle concentration condition, both a short average random range and the steric effect of particles may screen the guiding effect.

Key words: Long range van der Waals forces, Attraction driven cluster aggregation, Directionalism, Steric effect