Self-Diffusion in Supercooled Binary Liquids.

Abstract

Frequency-dependent self-diffusion coefficients ${D}_{s}(\ensuremath{\omega})$ for both particle species of a supercooled binary hard-sphere liquid have been calculated within a mode-coupling approximation. For a disparate-size mixture we find a glass transition at a critical packing fraction ${\ensuremath{\eta}}_{B}$ in connection with the localization of the large particles only. The small spheres retain a finite mobility within the glass. It is found that a little bump appears in ${D}_{s}(\ensuremath{\omega})$ of the small particles at low frequencies when the glass transition is approached, which implies that the diffusion mechanism of the small particles changes from fast liquidlike diffusion to slow diffusion in a random potential.