Hopping time of a hard disk fluid in a narrow channel.

We use Monte Carlo (MC) and molecular dynamics (MD) methods to study the self-diffusion of hard disk fluids, confined within a narrow channel. The channels have a pore radius of Rp, above the passing limit of hard disk diameter (sigma(hd)). We focus on the average time (tau(hop)) needed for a hard disk to hop past a nearest neighbor in the longitudinal direction. This parameter plays a key role in a recent theory of the crossover from single-file diffusion to the bulk limit. For narrow channels near the hopping threshold (Rp=1 in units of sigma(hd)), both MC and MD results for tau(hop) diverge as approximately (Rp-1)(-2). Our results indicate that the scaling law exponent does not appear to be dependent on the differences between the two dynamics. This exponent is consistent with the prediction of an approximate transition state theory.