**************** The 9th., Lab Seminar *****************

Date: Mon, July 25, 2005  PM 1:30-

Place: No.616 Seminar room
　　　　　　 Graduate School of Information Science

Speaker: Takuya Okamoto

Title: Short-time self-diffusion in dilute suspensions of highly charged colloids

Abstract:
 tatistical-mechanical theory of short-time self-diffusion
in dilute suspensions of highly charged colloids
The short-time self-diffusion of highly charged colloids is studied
theoretically. Generalized Langevin equations for the momenta of colloids are
derived from a statistical.mechanical point of view. The mean-square
displacement of colloids is then calculated for short times. The finite size
effect of small ions on short-time self-diffusion of colloids is thus
investigated. The short-time self-diffusion coefficient is shown to
decrease as the ratio of a single diffusion coefficient of a colloid to that of a
small ion increases. The dependence of the short-time dynamics on charges and volume
fractions is also discussed. The present theory is valid even for such small
ions which do not satisfy the so-called Stokes-Einstein relation. For
medium size of small ions which satisfy that relation, the validity of the theory
is confirmed by Brownian-dynamics simulations.

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