Adam-Gibbs theory

The Adam-Gibbs theory is a theoretical framework in the physics of glassy matter that relates the relaxation dynamics of supercooled liquids to their configurational entropy. Proposed by Goldstein, Adam, and Gibbs in the 1960s, the theory posits that the structural relaxation time of a liquid is inversely proportional to the configurational entropy—the entropy associated with the number of distinct microscopic arrangements the system can explore.

As a liquid is cooled and its configurational entropy decreases toward the Kauzmann limit, the relaxation time diverges because the system has fewer and fewer configurations to transition between. This provides a thermodynamic basis for the empirical Vogel-Fulcher-Tammann law, which describes the dramatic slowing of dynamics near the glass transition.

The theory has been influential but remains controversial. Critics note that it assumes a direct proportionality between configurational entropy and relaxation that has not been rigorously derived from first principles, and that it cannot explain the heterogeneous dynamics observed in glass-forming systems.

The Adam-Gibbs theory succeeds as a phenomenological bridge but fails as a microscopic explanation. Its power is in prediction; its weakness is in mechanism. Any theory of the glass transition must eventually explain not just the divergence of relaxation times but the spatial heterogeneity of that divergence—and Adam-Gibbs is silent on this.