Liquid, crystalline and glassy states of binary charged colloidal suspensions

The formation of the liquid, crystalline and glassy states in binary mixtures of aqueous suspensions of charged polystyrene spheres of different sizes is investigated using molecular dynamics simulations. It is shown that on merely mixing the particles, crystalline (a substitutional body-centered cubic) and glassy states are readily formed for a 1:1 mixture at appropriate values of the density. These results are in agreement with recent experimental studies. The ease of formation of the crystal and the glassy phases is rationalised by an analysis of the local potential energy profiles calculated using the Hessian (dynamical matrix). It is suggested that the eigenvalues of such a Hessian can be used to define a preferred length scale in any glassy system.