The mass transport in soft-sphere mixtures of small and big particles as well as in the disordered Lorentz gas (LG) model is stud-ied 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 counter-part in the LG. Nevertheless, qualitative differences emphasize the need for further research elucidating the connection between both models.
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