General two-parameter model of alpha-relaxation in glasses

In the vicinity of the glass transition, the characteristic relaxation time (e.g., the α-relaxation time in dielectric spectroscopy) of a glass-former exhibits a strongly super-Arrhenius temperature dependence, as compared to the classical Arrhenius behavior at high temperatures. A comprehensive description of both regions thus requires five parameters. Here, we demonstrate that many glass formers exhibit a general scaling, with only two material-specific parameters setting the timescale and the temperature scale; the other three being material-independent constants. Furthermore, we show that the master curve can be described by the recently developed two-state, two-(time) scale (TS2) theory [V. Ginzburg, Soft Matter 16, 810 (2020)10.1039/C9SM01575B] and regress the general TS2 parameters. We also show the connection between the TS2 model and the Hall-Wolynes elastic relaxation theory.