Many-body interactions in colloidal suspensions

At low ionic strength the interaction between any two charged colloids in a concentrated charge-stabilized suspension is strongly influenced by the charge distributions of other colloids in the neighbourhood of the two interacting colloids. When such many-body interactions become important, a colloidal suspension can no longer be treated as a simple Yukawa liquid. We here (i) discuss experimental data showing that many-body interactions are indeed present in low-salt-content colloidal suspensions, (ii) report on three-body calculations in colloidal systems that help in understanding the concept of 'macroion shielding', (iii) demonstrate the configuration dependence of effective forces and (iv) illustrate, using simulations based on (a) a truncated Yukawa potential with a density-dependent cut-off and (b) a full Poisson–Boltzmann mean-field description, the effect of many-body interactions on the solid–liquid phase behaviour of colloidal suspensions.