Are rare, long waiting times between rearrangement events responsible for the slowdown of the dynamics at the glass transition?

作者：Ahn Ji Won^*; Falahee Bryn; Del Piccolo Chiara; Vogel Michael; Bingemann Dieter

来源：Journal of Chemical Physics, 2013, 138(12): 12A527.

DOI：10.1063/1.4775740

The dramatic slowdown of the structural relaxation at the glass transition is one of the most puzzling features of glass dynamics. Single molecule orientational correlation times show this strong Vogel-Fulcher-Tammann temperature dependence typical for glasses. Through statistical analysis of single molecule trajectories, we can identify individual glass rearrangement events in the vicinity of a probe molecule in the glass former poly(vinyl acetate) from 8 K below to 6 K above the glass transition temperature. We find that changes in the distribution of waiting times between individual glass rearrangement events are much less dramatic with temperature, the main difference being a small, but decisive number of increasingly long waiting times at lower temperatures. We notice similar individual, local relaxation events in molecular dynamics trajectories for a variety of glassy systems further from the glass transition, leading to waiting time distributions with similar features as those observed in the single molecule experiments. We show that these rare long waiting times are responsible for the dramatic increase in correlation time upon cooling.

• 出版日期2013-3-28