- and -relaxations in supercooled binary liquids

Abstract

The - and -relaxations in a disparate-size binary liquid near the glass transition have been investigated within a mode-coupling theory. We focus our attention on the - and -peaks in the frequency-dependent susceptibility and their dependence on the concentrations of big and small particles. For the 1:1 mixture of big and small particles (size ratio = 0.2), a large peak appears in the susceptibility of the small particles in the frequency range of the -relaxation, which corresponds to the fast relaxation of the small particles within the random potential produced by the big particles. The intensity of this peak grows further as the concentration of the small particles is decreased. For large , on the other hand, the peak becomes lower than the -peak and the susceptibility is similar to that of a one-component liquid.