Using a radiotracer technique in conjunction with ion beam sputtering, we h
ave measured the concentration dependence of Co-57 diffusion in CoxZr1-x gl
asses for 0.3 less than or equal to x less than or equal to 0.86. The conce
ntration dependence at 573 K shows a strong variation over more than three
orders of magnitude with a pronounced minimum near x = 0.65. This reflects
structural changes, which are consistent with recent molecular dynamics sim
ulations and other investigations. The effect of structure on the diffusion
mechanism is discussed, in particular in connection with pressure dependen
ce and isotope effect measurements.