DYNAMICAL TEST OF INTERACTION POTENTIALS FOR COLLOIDAL SUSPENSIONS

An analytical formula for the ratio between the long- and short-time s elf-diffusion coefficient D-L/D-S is presented as a result of extensiv e Brownian dynamics simulations for Yukawa systems. In addition, force d Rayleigh scattering experiments are performed to determine D-L/D-S f or suspensions of highly charged latex spheres with a variable low vol ume fraction immersed in electrolytes of variable concentration. Exper imental parameters were precisely controlled using advanced preparatio nal methods. Comparing experimental data to the analytical formula we perform a sensitive dynamical test of Yukawa models for the interactio n potential. The observed quantitative agreement provides strong evide nce for the validity of the renormalization procedures suggested withi n the Poisson-Boltzmann cell model [J. Chem. Phys. 80, 5776 (1984)]. D eviations observed for the Dejarguin-Landau-Verwey-Overbeek potential and other models are discussed.