- Title题目 The role of hidden structural characteristics in glass-forming liquids: Two basic elements
- Speaker报告人 童华（中国科技大学物理学院）
- Date日期 2021年10月15日 15:00
- Venue地点 北楼322会议室
Glass transition takes place when a liquid is cooled fast enough to avoid crystallization, during which the viscosity (or structure relaxation time) increases by many orders of magnitude over a narrow temperature window, but without obvious structural change. The possible role of structural ordering in the drastic dynamical slowing down has been intensively discussed over the decades but remains elusive, due to the intrinsic difficulty in the description of the complex liquid structure. Here we tackle this fundamental problem by showing that two basic elements are essential to identify the role of hidden structural characteristics in glass-forming, namely a proper structural order parameter and a nonlocal scenario for the structure-dynamics correlation.
First, we introduce a new structural order parameter characterizing local packing capability and show that the fast relaxation is controlled by the structure at local level while the slow relaxatiuon is controlled by structural ordering at static correlation length . This result crucially establishes that the two key relaxation modes at two characteristic time scales are the consequence of the presence of the two intrinsic length scales in the structure.
Then, we show quantitatively that the growth of structural order when approaching the glass transition can be described by a linear scaling law as a function of temperatur, which leads to a universal Vogel-Fulcher-Tammann (VFT)-like relation between the relaxation time and the structural order parameter. More importantly, we find, based on the nonlocal scenario of structure-dynamics correlation, that such an intriguing VFT-like relation to be valid even at a particle level. We expect this nonlocal mechanism of structure relaxation, in addition to the hidden structural ordering, to be two essential ingredients for a complete theoretical description of the glass transition as a special type of thermodynamic phase transition.