Structure and kinetics in colloidal films with competing interactions

Abstract

Using computer simulation we explore how two-dimensional systems of colloids with a combination of shortrange attractive and long-range repulsive interactions generate complex structures and kinetics. Cooperative effects mean the attractive potential, despite being very short-ranged compared to the repulsion, can have significant effects on large-scale structure. By considering the number of particles occupying a notional "repulsion zone" defined by the repulsion length scale, we classify different characteristic structural regimes in which the combination of attraction and repulsion leads to different structural and kinetic outcomes, such as compact clustering, chain labyrinths, and coexisting clusters and chains. In some regimes small changes in repulsion range and/or area fraction can change timescales of structural evolution by many orders of magnitude.

Patterns in magnetic granular media at the crossover from two to three dimensions

“…As expected, the increase of the cell height h leads to consecutive structural transitions from a crystalline arrangement toward disordered individual grains that eventually gather into long chains of several particles and form labyrinthine patterns. Similar structures were reported previously both experimentally for paramagnetic grains and colloids [27][28][29] and numerically for systems with particles interacting by a combination of long-range repulsion and short-range attraction [36,37], a combination of hard-and soft-core repulsion [38], or dipolar interactions [29,39].…”