Direct structural evidence for dynamic heterogeneity in supercooled liquid bulk metallic glass

In situ measurements of the X-ray absorption fine structure for the supercooled liquid state of Au65Cu10.5Si17Ag7.5 bulk metallic glass, which exhibits extraordinarily low Tg and a stable supercooled liquid state, were performed. Analyses of data combined with molecular dynamics simulation suggest that the glass transition is caused by the breakdown of Cu–Cu bonding which connects Cu-centered icosahedral clusters. Cu atoms play a key role in the enhancement of glass formability and the low Tg of the Au65Cu10.5Si17Ag7.5 bulk metallic glass.