Thermodynamic universality of configurational entropy in glass-forming liquids

Glass is a liquid-like disordered material but behaves mechanically like a solid. Ubiquitous in nature and important in technology, the vitreous state manifests its presence from window glass, polymers, to optical fiber, and almost all kinds of materials have ability to form glass. Significant progress has been made in understanding the nature of the phenomenon, yet the issue remains a major scientific challenge. Here we propose one concise, explicit thermodynamic expression in both temperature and pressure for the configurational entropy of the Adam-Gibbs theory, and show its excellent universal description of experimental data. The formulation generalizes the most important equations in the field such as the VFT equation, judiciously unifies for the first time the two key thermodynamic variables in one form, has non-divergence which resolves the long-standing Kauzmann paradox, tentatively provides a sound foundation addressing the mutual effects of temperature and pressure, and predicts the glass transition as a second-order phase transition. This approach should thus offer an organizing principle to rationalize the vast body of dynamic properties and advance researches on the thermodynamics including the glass transition of glass-forming substances.