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Published on: March 6, 2017
On the Williams-Watts function of dielectric relaxation
1Office of Naval Research, 800 North Quincy Street, Arlington, VA 22217.
Summary
The Williams-Watts polarization decay function accurately describes dielectric constants in polymers and glasses. A new random-walk model explains this function, linking material properties to molecular relaxation dynamics.
Area of Science:
- Materials Science
- Statistical Physics
- Dielectric Spectroscopy
Background:
- Experimental frequency-dependent dielectric constants in polymers and glasses are often described by the Williams-Watts polarization decay function.
- This function's parameters, alpha and T, are material-dependent and influenced by external conditions like temperature and pressure.
Purpose of the Study:
- To derive the Williams-Watts polarization decay function from a microscopic random-walk model.
- To provide a theoretical explanation for the observed dielectric behavior in various materials.
Main Methods:
- A random-walk model involving mobile defects and frozen dipoles was developed.
- The model simulates defect diffusion as a continuous-time random walk with a specific pausing-time distribution.
Main Results:
- The random-walk model successfully reproduces the fractional exponential form of the Williams-Watts polarization decay function.
- The model establishes a connection between defect dynamics and macroscopic dielectric relaxation.
Conclusions:
- The study provides a theoretical foundation for the Williams-Watts function based on defect-mediated molecular reorientation.
- This work offers insights into the relationship between microscopic dynamics and dielectric properties of materials.
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