Effect of bond lifetime on the dynamics of a short-range attractive colloidal system.

We perform molecular dynamics simulations of short-range attractive colloid particles modeled by a narrow (3% of the hard sphere diameter) square well potential of unit depth. We compare the dynamics of systems with the same thermodynamics but different bond lifetimes, by adding to the square well potential a thin barrier at the edge of the attractive well. For permanent bonds, the relaxation time tau diverges as the packing fraction phi approaches a threshold related to percolation, while for short-lived bonds, the phi dependence of tau is more typical of a glassy system. At intermediate bond lifetimes, the phi dependence of tau is driven by percolation at low phi , but then crosses over to glassy behavior at higher phi . We also study the wave vector dependence of the percolation dynamics.