Density profiles of colloidal suspensions in equilibrium inside slit pores

Abstract

The problem of sedimentation equilibrium is treated within the integral equation formalism of inhomogeneous fluids using the Ornstein-Zernike approach, and using the Percus-Yevick closure, to describe sterically stabilized and charged colloidal suspensions contained in pores of different size. The calculated density profiles exhibit pronounced oscillations near the bottom, showing layering, and, for large pores, a non-oscillatory tail, in agreement with Monte Carlo simulations. For small pores, the particle distribution includes the appearance of layers for small separations. In the case of bidispersions, the computation shows that for large pores there is non-monotonic behaviour by one of the components, owing to competition between excluded volume and gravity. A similar effect is shown in monocomponent systems if the particles interact via a Yukawa-type potential.