  Based on Brownian Dynamics computer simulations in two dimensions we
investigate aggregation scenarios of colloidal particles with directional
interactions induced by multiple external fields. To this end we propose a
model which allows continuous change in the particle interactions from
point-dipole-like to patchy-like (with four patches). We show that, as a result
of this change, the non-equilibrium aggregation occurring at low densities and
temperatures transforms from conventional diffusion-limited cluster aggregation
(DLCA) to slippery DLCA involving rotating bonds; this is accompanied by a
pronounced change of the underlying lattice structure of the aggregates from
square-like to hexagonal ordering. Increasing the temperature we find a
transformation to a fluid phase, consistent with results of a simple mean-field
density functional theory.
