Collective diffusion, self-diffusion and freezing criteria of colloidal suspensions

BANCHIO, A. J.; NÄGELE, G.; BERGENHOLTZ, J.

JOURNAL OF CHEMICAL PHYSICS

Año: 2000 vol. 113 p. 3381 - 3381

0021-9606

In this paper, we examine collective and self-diffusion properties of dispersions of sphericallyshaped colloidal particles at intermediate and long times. Our analysis is based on a fullyself-consistent ~rescaled! mode coupling theory (MCT) adjusted to describe the overdampeddynamics in concentrated suspensions of neutral and charged colloidal particles. The dynamicalquantities studied in dependence on various experimentally controllable system parameters are theparticle mean-squared displacement, long-time collective and self-diffusion coefficients, dynamicstructure factors, nonexponentiallity factors and collective and self-memory functions. The resultsof our theoretical treatment are compared with Brownian dynamics computer simulation data,experiment and other existing theories. It is shown that the rescaled MCT can be successfullyapplied to a wide range of dynamical properties. Our calculations reveal in particular an exponentiallong-time mode of the dynamic structure factor for a limited range of wave numbers and atsufficiently high concentrations. A dynamic scaling behavior of the dynamic structure factor andself-intermediate scattering function is predicted for the important case of salt-free charge-stabilizedsuspensions. As a consequence of the dynamic scaling, the static freezing criterion for colloids byHansen and Verlet [Phys. Rev. 184, 151 (1969)] is shown to be equivalent with the dynamiccriterion by Lo¨wen et al. [Phys. Rev. Lett. 70, 1557 (1993)] related to long-time self-diffusion.