Dynamical test of interaction potentials for colloidal suspensions

Abstract

An analytical formula for the ratio between the long- and short-time self-diffusion coefficient ${\mathit{D}}_{\mathit{L}}$/${\mathit{D}}_{\mathit{S}}$ is presented as a result of extensive Brownian dynamics simulations for Yukawa systems. In addition, forced Rayleigh scattering experiments are performed to determine ${\mathit{D}}_{\mathit{L}}$/${\mathit{D}}_{\mathit{S}}$ for suspensions of highly charged latex spheres with a variable low volume fraction immersed in electrolytes of variable concentration. Experimental parameters were precisely controlled using advanced preparational methods. Comparing experimental data to the analytical formula we perform a sensitive dynamical test of Yukawa models for the interaction potential. The observed quantitative agreement provides strong evidence for the validity of the renormalization procedures suggested within the Poisson-Boltzmann cell model [J. Chem. Phys. 80, 5776 (1984)]. Deviations observed for the Dejarguin-Landau-Verwey-Overbeek potential and other models are discussed.