A simple model of tracer-diffusion of nonspherical Brownian particles

Abstract

We present a Brownian dynamic simulation of the translational and rotational motion of an interacting nonspherical Brownian particle. This simulation experiment involves an idealized model system of a suspension of spherical colloidal particles with which the nonspherical particle interacts. The latter is represented as a rigid linear array of (two or three) spherical particles. The direct pair interactions between all the spheres in the system (including those of the tracer particle) are modeled by a repulsive Yukawa potential. For simplicity, the two-dimensional version of this simulation experiment is considered, and hydrodynamic interactions are ignored. From the simulation experiment, we determine the translational and rotational mean-square-displacement of the nonspherical tracer particle. Here we focus only on the early deviations, due to the direct interactions, from the short-time, free-diffusion regime. In the analysis of these results, use is made of the recently developed Generalized Langevin equation theory of tracer diffusion of nonspherical Brownian particles.