The glass transition involves only a minor change in the internal energy, and yet the physical and mechanical properties of the glass change dramatically. Atomic bonding behavior is critical to understanding these interesting changes. In order to determine the evolution of the atomic structure through the glass transition, we employed in situ synchrotron x-ray scattering measurements as a function of temperature on a model material—Zr-Cu-Al metallic glass. Based upon the study of pair distribution function and the characterization of the free volume in terms of atomic bonding lengths, we found that the relative change of the quantity, Δ$N$/$N$ ($N$ represents the number of atom pairs), with significantly longer interatomic distances for the nearest atomic pairs, increases abruptly above the glass transition temperature ($T_g$). These phenomena are interpreted in terms of the tight-bond cluster model developed recently.

• Received 23 January 2011

DOI:https://doi.org/10.1103/PhysRevB.83.195207