Minimal model for Beta relaxation in viscous liquids

Area of Science:

• Condensed matter physics
• Materials science
• Physical chemistry

Background:

• Beta relaxation is a key dynamic process in viscous liquids and glasses.
• Understanding the differences between liquid and glass dynamics is crucial for materials science.
• Hysteresis observed during glass transitions complicates dynamic analysis.

Purpose of the Study:

• To rationalize the contrasting behaviors of beta relaxation in equilibrium viscous liquids and glasses.
• To propose and test a theoretical model explaining these dynamic differences.
• To investigate the phenomenon of hysteresis in dielectric loss during glass transitions.

Main Methods:

• Development of a double-well potential model with structure-dependent asymmetry.
• Description of material structure using a single order parameter.
• Application and testing of the model to experimental data for tripropylene glycol.

Main Results:

• The double-well potential model successfully rationalizes the contrasts between beta relaxation in liquids and glasses.
• The model accounts for the observed hysteresis in the dielectric beta loss peak frequency and magnitude for tripropylene glycol.
• Structure-dependent asymmetry in the potential is identified as a key factor.

Conclusions:

• The proposed double-well potential model provides a unified framework for understanding beta relaxation dynamics across the liquid-glass transition.
• The model's success in explaining hysteresis highlights its predictive power for glassy materials.
• Further studies can explore the application of this model to other amorphous systems.