We report on a comprehensive theory-simulation-experimental study ofcollective and self-diffusion in suspensions of charge-stabilized colloidalspheres. In simulation and theory, the spheres interact by a hard-core plusscreened Coulomb pair potential. Intermediate and self-intermediate scatteringfunctions are calculated by accelerated Stokesian Dynamics simulations wherehydrodynamic interactions (HIs) are fully accounted for. The study spans therange from the short-time to the colloidal long-time regime. Additionally,Brownian Dynamics simulation and mode-coupling theory (MCT) results aregenerated where HIs are neglected. It is shown that HIs enhance collective andself-diffusion at intermediate and long times, whereas at short timesself-diffusion, and for certain wavenumbers also collective diffusion, areslowed down. MCT significantly overestimate the slowing influence of dynamicparticle caging. The simulated scattering functions are in decent agreementwith our dynamic light scattering (DLS) results for suspensions of chargedsilica spheres. Simulation and theoretical results are indicative of along-time exponential decay of the intermediate scattering function. Theapproximate validity of a far-reaching time-wavenumber factorization of thescattering function is shown to be a consequence of HIs. Our study ofcollective diffusion is amended by simulation and theoretical results for theself-intermediate scattering function and the particle mean squareddisplacement (MSD). Since self-diffusion is not assessed in DLS measurements, amethod to deduce the MSD approximately in DLS is theoretically validated.
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