Dynamic scattering function of a dense suspension of hard spheres

We study the time-dependent intermediate scattering function of a dense colloidal suspension of hard spheres with neglect of hydrodynamic interactions. The dynamics of the suspension is assumed to be governed by the generalized Smoluchowski equation. The Laplace transform of the scattering function involves the static structure factor and an irreducible memory kernel. The latter is calculated approximately from an equation of the Enskog type, involving the diffusion of two hard spheres and the value of the equilibrium radial distribution function at touching. We find excellent agreement with the results of computer simulation up to a volume fraction of about forty percent.