Evaluation of heterogeneity measures and their relation to the glasstransition

For most phase transitions, dynamic slowdown is accompanied by a static structure change. However, in the case of the supercooled liquid, which is a special liquid state below the melting temperature, one observes pronounced dynamic slowdown, i.e., diffusion coefficient, relaxation time, and viscosity change 10-14 orders of magnitude within a relatively small temperature range. This occurs without the pronounced static structure change observed in other phase transitions. Over the past several decades, there has been extensive research aimed to understand why the glass transition occurs, to establish what the glass transition exactly is, and to improve our understanding of how molecules move near to the glass transition. In the present work, we have examined the idea that the dramatic reduction in molecular mobility or dynamic slowdown in a supercooled liquid during cooling from above T-g occurs because of the increasing length scale of heterogeneous subregions, or the cooperatively r