A remark on the negative activation volume for defects in solids

TL;DR

This paper explains the phenomenon of negative defect activation volumes in solids using a thermodynamical model, extending previous understanding of glassy material aging and volume-enthalpy relationships.

Contribution

It demonstrates that a thermodynamical model can account for negative defect activation volumes, a rare phenomenon in solid defect dynamics.

Findings

Negative defect activation volumes can be explained thermodynamically.

The model links aging behavior of glasses to defect activation properties.

Empirical observations of volume-enthalpy slopes are supported by the model.

Abstract

The evolution of the aging process of glassy materials quenched from temperatures above their glass transition temperature $T_g$, when plotting the relaxed enthalpy versus the decrease in volume, leads to a slope comparable to the isothermal compressibility close to $T_g$. This empirical result was explained in an earlier publication (V. Katsika-Tsigourakou, G. E. Zardas J. Non-Cryst. Solids 356 (2010) 179-180) by means of a thermodynamical model. Here, we show that the same model enables the explanation of the rare cases of negative defect activation in solids.