  The mass transport in soft-sphere mixtures of small and big particles as well
as in the disordered Lorentz gas (LG) model is studied using molecular dynamics
(MD) computer simulations. The soft-sphere mixture shows anomalous
small-particle diffusion signifying a localization transition separate from the
big-particle glass transition. Switching off small-particle excluded volume
constraints slows down the small-particle dynamics, as indicated by incoherent
intermediate scattering functions. A comparison of logarithmic time derivatives
of the mean-squared displacements reveals qualitative similarities between the
localization transition in the soft-sphere mixture and its counterpart in the
LG. Nevertheless, qualitative differences emphasize the need for further
research elucidating the connection between both models.
