Nonequilibrium structure and rheology of concentrated colloidal suspensions: Linear response

We propose a simple theory for the pair distribution function of a sheared colloidal suspension. The starting point is an exact equation for the stationary state pair distribution. We assume that in a shear flow the higher order distributions can be expressed through the pair distribution in the same way as in an equilibrium state. To get explicit results we use a simple decoupling approximation for the higher order equilibrium correlations. For moderate volume fractions our theory predicts low-shear viscosity that agrees well with Brownian Dynamics simulations results. Low-shear distortion of the pair structure is underestimated by the theory but its shape agrees qualitatively with the simulations.