Glassy Aging with Modified Kohlrausch-Williams-Watts Form

TL;DR

This paper proposes a new model for glassy aging that directly relates relaxation time to aging, fitting experimental data with a different stretching exponent than the alpha-relaxation, challenging previous assumptions about aging control.

Contribution

It introduces an alternative functional form for modeling glassy aging, directly involving relaxation time and differing from prior models by using a distinct stretching exponent.

Findings

The new model fits experimental aging data perfectly.

The stretching exponent in the model differs from the alpha-relaxation exponent.

Aging in glassy states may not be solely controlled by alpha-relaxation.

Abstract

In this report we address the question whether aging in the non equilibrium glassy state is controlled by the equilibrium alpha-relaxation process which occur at temperatures above Tg. Recently Lunkenheimer et. al. [Phys. Rev. Lett. 95, 055702 (2005)] proposed a model for the glassy aging data of dielectric relaxation using a modified Kohlrausch-Williams-Watts (KWW) form. The aging time dependence of the relaxation time is defined by these authors through a functional relation involving the corresponding frequency but the stretching exponent is same as the alpha-relaxation stretching exponent. We present here an alternative functional form directly involving the relaxation time itself. The proposed model fits the data of Lunkenheimer et. al. perfectly with a stretching exponent different from the alpha-relaxation stretching exponent.