Size dependence of self-diffusion in a dense hard-disc liquid

For a binary liquid mixture of hard discs well above the freezing density of the one-component liquid the size dependence of the self-diffusion coefficients of small and large particles is calculated by molecular dynamics simulation. The observed size effect can be satisfactorily explained by the size-dependent cut-off of long-wavelength fluctuations of transverse collective flow and gives no indication of the importance of more 'cooperative' processes at high densities.