Aggregation of binary colloidal suspensions on attractive walls

The adsorption of colloidal particles from a suspension on a solid surface is of fundamental importance to many physical and biological systems. In this work, Brownian Dynamics simulations are performed to study the aggregation in a suspension of oppositely charged colloidal particles in the presence of an attractive wall. For sufficiently strong attractions, the wall alters the microstructure of the aggregates so that B2 (CsCl-type) structures are more likely obtained instead of B1 (NaCl-type) structures. The probability of forming either B1 or B2 crystallites depends also on the inverse interaction range kappa a. Suspensions with small kappa a are more likely to form B2 crystals than suspensions with larger kappa a, even if the energetic stability of the B2 phase decreases with decreasing kappa a. The mechanisms underlying this aggregation and crystallization behaviour are analyzed in detail.