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We study the combined effects of electrostatic and hydrodynamic interactions (HI) on the short-time dynamics of charge-stabilized colloidal spheres. For this purpose, we calculate the translational and the rotational self-diffusion coefficients, $D^t_s$ and $D^r_s$, as function of volume fraction $\phi$ for various values of the effective particle charge $Z$ and various concentrations $n_s$ of added 1--1 electrolyte. Our results show that the self-diffusion coefficients in deionized suspensions are less affected by HI than in suspensions with added electrolyte. For very large $n_s$, we recover the well-known results for hard spheres, i.e. a linear $\phi$-dependence of $D^t_s$ and $D^r_s$ at small $\phi$. In contrast, for deionized charged suspensions at small $\phi$, we observe the interesting non-linear scaling properties $D^t_s\propto1-a_t\phi^{4/3}$ and $D^r_s\propto 1-a_r\phi^2$. The coefficients $a_t$ and $a_r$ are found to be nearly independent of $Z$. The qualitative differences between the dynamics of charged and uncharged particles can be well explained in terms of an effective hard sphere (EHS) model., Comment: 4 pages, LaTeX, 3 Postscript figures included using epsf

We report on calculations of the reduced sedimentation velocity $U/U_{0}$ in homogenous suspensions of strongly and weakly charged colloidal spheres as a function of particle volume fraction $\phi$. For dilute suspensions of strongly charged spheres at low salinity, $U/U_{0}$ is well represented by the parametric form $1-p\phi^\alpha$ with a fractional exponent $\alpha=1/3$ and a parameter $p\simeq 1.8$, which is essentially independent from the macroion charge $Z$. This non-linear volume fraction dependence can be quantitatively understood in terms of a model of effective hard spheres with $\phi$-dependent diameter. For weakly charged spheres in a deionized solvent, we show that the exponent $\alpha$ can be equal to 1/2, if an expression for $U/U_0$ given by Petsev and Denkov [J. Colloid Interface Sci. 149, 329 (1992)] is employed. We further show that the range of validity of this expression is limited to very small values of $\phi$ and $Z$, which are probably not accessible in sedimentation experiments. The presented results might also hold for other systems like spherical proteins or ionic micelles., Comment: 15 pages and 8 figures, final version as published