Comparing models for diffusion in supercooled liquids: The
eutectic composition of the Ag-Cu alloy
Charles F. Vardeman II and J. Daniel Gezelter
Department of Chemistry and Biochemistry
University of Notre Dame
Notre Dame, Indiana 46556
We present a comparison between the Continuous Time Random Walk (CTRW)
model for dispersive transport and Zwanzig's model of
self-diffusion in liquids [R. Zwanzig, J. Chem. Phys.
79, 4507 (1983)] using the cage correlation function as a means for
obtaining the characteristic hopping times. This comparison was done
using a realistic model for the interactions between metal atoms in a
system which is known to form metallic glasses. We find that although
the CTRW model uses a pathological model for the distribution of
waiting times, the predictions of this theory are much closer to the
actual diffusion constants than those obtained via Zwanzig's model.
We also find that there is a simple linear relationship between the
stretching parameter ß for Kohlrausch-Williams-Watts decay of
the cage correlation function and the dispersion parameter (gamma)
that characterizes the ``fractal'' distribution of waiting times in
the CTRW model.
