Diffusion of Classical Particles in a Random Medium. II. Nonlinear Response

Abstract

A formalism developed in a preceding paper [J. Phys. Soc. Jpn. 51 (1982) 1482.] is extended and applied to a nonlinear response of a single classical particle diffusing in a random array of medium particles which behave as obstructions or traps. The expressions of the mobility in second and inverse-second order in the strength of the external force are derived on the basis of a given radial distribution function of medium particles. The mobility is calculated explicitly for hard-sphere and attractive Gaussian core systems and influence of short-range order between medium particles is revealed. For hard-sphere systems, the calculations show that the strong external force causes the capture of the diffusing particle in gaps formed by medium particles.