Double transition scenario for anomalous diffusion in glass-forming mixtures.

We study by molecular dynamics computer simulation a binary soft-sphere mixture that shows a pronounced difference in the species' long-time dynamics. Anomalous, power-law-like diffusion of small particles arises that can be understood as a precursor of a double-transition scenario, combining a glass transition and a separate small-particle localization transition. Switching off small-particle excluded-volume constraints slows down, rather than enhances, small-particle transport.