On the application of the Adam–Gibbs equation to the non-equilibrium glassy state

A new extension of the Adam–Gibbs (AG) equation to the non-equilibrium glassy state is presented, whereby the configurational entropy is a function of both fictive temperature and thermodynamic temperature. The relative contributions of each are determined by an entropic non-linearity parameter x _s analogous to the non-linearity parameter x of the Tool–Narayanaswamy–Moynihan (TNM) equation. This new form of the AG equation resolves many inconsistencies in the TNM approach: for example, the dependence of x on annealing temperature and time observed by many workers, as well as often unreasonable values for x and for T ₂. Furthermore, it can rationalise the frequently reported correlation between x and β, the KWW non-exponentiality parameter. A physical interpretation of x _s is made in terms of the Gibbs–DiMarzio theory and the relative importance of the freezing-in of either holes or of high energy bond conformations.