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Dynamical heterogeneity in a highly supercooled liquid under a sheared situation
Hideyuki Mizuno1, Ryoichi Yamamoto
1Department of Chemical Engineering, Kyoto University, Kyoto 615-8510, Japan. h-mizuno@cheme.kyoto-u.ac.jp
The Journal of Chemical Physics
|March 3, 2012
Summary
Steady shear flow reduces dynamical heterogeneity in supercooled liquids. Key measures like correlation length and lifetime decrease with increasing shear rate, suggesting a universal role for heterogeneity in relaxation dynamics.
Area of Science:
- Condensed Matter Physics
- Soft Matter Physics
- Computational Materials Science
Background:
- Dynamical heterogeneity is a key feature of supercooled liquids, influencing their relaxation dynamics.
- Understanding how external fields like shear flow affect this heterogeneity is crucial for materials science.
Purpose of the Study:
- To investigate the impact of steady shear flow on dynamical heterogeneity in supercooled liquids.
- To quantify the changes in correlation length, intensity, and lifetime of dynamical heterogeneity under shear.
Main Methods:
- Molecular dynamics simulations were employed to model supercooled liquid behavior.
- Four-point correlation functions were extended to analyze particle dynamics under steady shear flow.
- Local dynamics were defined using the alpha-relaxation time (τ(α)) and the time of maximum non-Gaussian parameter (τ(ngp)).
Main Results:
- All three measures of dynamical heterogeneity (correlation length ξ(4)(t), intensity χ(4)(t), and lifetime τ(hetero)(t)) decrease with increasing shear rate (γ).
- Specific scaling relations were found: ξ(4)(τ(α))~γ(-0.08), χ(4)(τ(α))~γ(-0.26), and τ(hetero)(τ(α))~γ(-0.88).
- Steady shear flow was shown to suppress both the heterogeneous structure and its lifetime.
Conclusions:
- Dynamical heterogeneity in supercooled liquids is suppressed by steady shear flow.
- The behavior of dynamical heterogeneity under shear can be mapped to equilibrium conditions using the alpha-relaxation time (τ(α)).
- Dynamical heterogeneity plays a significant role in the shear-rate-dependent relaxation dynamics of supercooled liquids, similar to its role in temperature-dependent dynamics.
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