  Using dynamical density functional theory (DDFT), we theoretically study
Brownian self-diffusion and structural relaxation of hard disks and compare to
experimental results on quasi two-dimensional colloidal hard spheres. To this
end, we calculate the self and distinct van Hove correlation functions by
extending a recently proposed DDFT-approach for three-dimensional systems to
two dimensions. We find that the theoretical results for both self- and
distinct part of the van Hove function are in very good quantitative agreement
with the experiments up to relatively high fluid packing fractions of roughly
0.60. However, at even higher densities, deviations between experiment and the
theoretical approach become clearly visible. Upon increasing packing fraction,
in experiments the short-time self diffusive behavior is strongly affected by
hydrodynamic effects and leads to a significant decrease in the respective
mean-squared displacement. In contrast, and in accordance with previous
simulation studies, the present DDFT which neglects hydrodynamic effects, shows
no dependence on the particle density for this quantity.
