The interactions in highly charged colloidal systems are essentially governed by their number of effective charges and the Debye length related to the ionic strength resulting from the colloidal macroions' counter ions and possibly from stray ions. Since the particle size only marginally influences the interactions, in mixtures of equally charged species with different sizes, the interactions between all species are practically identical. Different particle sizes, however, lead to different short-time mobilities whose propagation to long-time dynamics is investigated by means of Brownian dynamics simulation and mode coupling theory. Both, in simulations and MCT dynamic coupling effects mediated by electrostatic interactions are observed: In presence of a smaller species, the long-time dynamics of a larger species is accelerated and vice versa as visible both in self- and collective dynamics.
Despite MCT predictions for dynamic quantities are in qualitative agreement with simulations, also for these Yukawa systems, the tendency of MCT to overestimate memory effects is observed. Using structure factors of systems with reduced interactions, i.e., reduced number of effective charges preserving the number density and therewith interparticle distances, a nearly quantitative agreement of various dynamic observables between MCT and simulation is achieved. We compare structure factors from simulation and thermodynamic consistent integral equations with Rogers-Young closure. Adjusting a free mixing parameter in this closure relation using a priori information leads to considerable agreement of structure factors from simulation and integral equations for these highly dilute systems. For charged particles, their dimensionless isothermal compressibility and thus the low wave vector limit of the total structure factor is according to the Kirkwood-Buff realation in first approximation the inverse number of total charges.