| Abstract Scope |
The conventional view on the atomic dynamics in glass and liquid is that it is controlled by confinement or caging by the near neighbor atoms. However, recent data suggest a different story. The near neighbors, characterized by the short-range order (SRO), are not totally frozen even in the glassy state, and about 20% of them retain a liquid-like character. Instead, the medium-range order (MRO), characterized by the oscillations in the pair-distribution function (PDF) beyond the first peak, controls the atomic dynamics including the glass transition. This is consistent with the observation that the relaxation of the first peak of the structure function, S(Q), the alpha-relaxation, closely tracks the bulk mechanical relaxation, because the MRO is well represented by the first peak of S(Q). The implication of this result on the role of structural defects in deformation is discussed. This work is supported by the US Department of Energy. |