COOPERATIVE JUMP MOTIONS IN COLLOIDAL GLASS

We report Brownian dynamics simulation results on binary colloidal mix tures of particles of two different diameters interacting via a repuls ive DLVO potential. As the effective temperature is lowered by reducin g charged impurity concentration, a transition from liquid to crystal at a total volume fraction phi of 0.2 and to glassy state at phi = 0.3 are observed. The mean squared displacements show a marked subdiffusi ve behavior at intermediate and long times below a certain temperature . The particle motion in supercooled liquid with phi = 0.3 is strongly cooperative as revealed by mean squared displacements, self-part of v an-Hove density correlation functions and non-Gaussian parameter. Inte restingly, a few particles exhibit cooperative hop and subsequent hop- back motion at temperatures very close to the glass transition.