According to mode coupling theory, liquid-like motion became frozen at a critical temperature Tc well above the caloric glass transition temperature Tg. Here, for the first time, radiotracer diffusion in a supercooled Pd43Cu27Ni10P20 alloy from Tg to the equilibrium melt was studied. Liquid-like motion was seen to set in exactly above Tc as reflected by a gradual drop in the effective activation energy. This strongly supported the mode-coupling scenario. Isotope effect measurements, which had never been carried out near to Tc in any material, showed atomic transport up to the equilibrium melt to be far away from the hydrodynamic regime of uncorrelated binary collisions.

Diffusion in a Metallic Melt at the Critical Temperature of Mode Coupling Theory. V.Zöllmer, K.Rätzke, F.Faupel, A.Meyer: Physical Review Letters, 2003, 90[19], 195502 (4pp)