Diffusion in a binary amorphous metal: Pair-correlation in Cu33Zr67

Diffusion in metallic glasses and their undercooled melts is a highly collective process which upon quenching passes from flow to hopping. In the undercooled liquid one can still describe diffusion by jumps which, however, are too rapid for the system to thermalize between jumps. In our previous work on diffusion in Cu33Zr67 we found that there are no preferred jump lengths in the system despite the observed side-peaks in the van-Hove correlation function. These are ascribed to longer waiting times between jumps caused by the different mobilities of atoms. Here we report results on the time and temperature evolution of the pair correlation functions. Whereas the Zr–Zr pair-correlation decays as one would expect from diffusion without a fixed step length, the Cu–Cu correlation behaves markedly different. Despite the higher Cu-mobility the Cu–Cu correlations decay slower than the Zr–Zr ones and the decay is not monotonous.