A Comparison of the Approach to Equilibrium of the Viscosity and Diffusivity of Pd--Si-Based Amorphous Metals

The diffusivity of gold in amorphous Pd sub 80 Si sub 20 thin films was measured near the glass transition temperature by Rutherford backscattering. Comparison of the results with viscosity data on Pd sub 77.5 Cu sub 6 Si sub 16.5 led to the following findings. The Stokes-Einstein relation between the equilibrium values does not hold, with the diffusivity being several orders of magnitude higher than predicted from the viscosity; van den Beukel's alternative relation ( eta D exp 2 = C), however, holds. The time constant for equilibrium of the viscosity is similar to that of the diffusivity near the glass transition temperature, but becomes several orders of magnitude greater at lower temperatures.