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Local-Average Free Volume Correlates with Dynamics in Glass Formers
Baicheng Mei1,2, Bilin Zhuang3, Yuyuan Lu1
1State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China.
The Journal of Physical Chemistry Letters
|April 28, 2022
Summary
Researchers found that local-average free volume strongly correlates with dynamic heterogeneity in glass formers. This resolves debates on the structural origins of slow dynamics near the glass transition.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Chemical Physics
Background:
- Glass-forming liquids exhibit significant slowdowns and increasing heterogeneity approaching the glass transition.
- A key debate concerns whether this dynamical slowdown arises from dynamical heterogeneity and its structural origins.
- Previous studies showed weak correlations between dynamical heterogeneity and single-particle free volume distribution.
Purpose of the Study:
- To investigate the relationship between structural properties and dynamic heterogeneity in glass-forming liquids.
- To determine if a purely structural origin for dynamic heterogeneity exists.
- To clarify the role of free volume in particle rearrangements during activated hopping relaxation.
Main Methods:
- Introduction of the 'local-average free volume' concept.
- Numerical simulations to analyze correlations between structural properties and dynamics.
- Examination of correlations over length scales of neighboring atomic shells.
Main Results:
- Long-time dynamic heterogeneity shows significantly enhanced correlation with the average local free volume.
- This correlation is observed over a length scale of a few neighboring shells.
- The findings suggest a stronger link between structural free volume and dynamic heterogeneity than previously thought.
Conclusions:
- Free volume plays a crucial role in particle rearrangements and activated hopping relaxation in glass formers.
- The concept of local-average free volume provides a better structural descriptor for dynamic heterogeneity.
- The 'local average' approach can be extended to other structural descriptors for analyzing glass-forming liquids.
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