Colloidal gelation, percolation and structural arrest

By means of molecular dynamics, we study a model system for colloidal suspensions where the interaction is based on a competition between attraction and repulsion. At low temperatures the relaxation time $\tau$ first increases as a power law as a function of the volume fraction $\phi$ and then, due to the finite lifetime of the bonded structures, it deviates from this critical behavior. We show that colloidal gelation at low temperatures and low volume fractions is crucially related to the formation of spanning long living cluster. Besides agreeing with experimental findings in different colloidal systems, our results shed new light on the different role played by the formation of long living bonds and the crowding of the particles in colloidal structural arrest.