Nonequilibrium effects on slow dynamics in concentrated colloidal suspensions.

Abstract

An alternative stochastic diffusion equation is proposed to study the dynamics of nonequilibrium density fluctuations in concentrated hard-sphere suspensions of interacting Brownian particles with both hydrodynamic and direct interactions among particles. The singularity of the correlation effect of the many-body hydrodynamic interactions is shown to drastically influence the qualitative behavior of the relaxation of nonequilibrium density fluctuations, and thus to cause the two different slow relaxations whose time scales, ${t}_{\ensuremath{\beta}}$ and ${t}_{\ensuremath{\alpha}}$, diverge as the volume fraction of Brownian particles approaches the critical value ${\ensuremath{\varphi}}_{c}=\frac{{(\frac{4}{3})}^{3}}{(7\mathrm{ln}3\ensuremath{-}8\mathrm{ln}2+2)}$; ${t}_{\ensuremath{\beta}}\ensuremath{\sim}{(1\ensuremath{-}\frac{\ensuremath{\varphi}}{{\ensuremath{\varphi}}_{c}})}^{\ensuremath{-}1}$ and ${t}_{\ensuremath{\alpha}}\ensuremath{\sim}{(1\ensuremath{-}\frac{\ensuremath{\varphi}}{{\ensuremath{\varphi}}_{c}})}^{\ensuremath{-}2}$.