The limitation for popular descriptions of alpha-relaxation temperature dependence
Abstract
Applicability of three popular functions (Vogel-Fulcher-Tammann, double activation law and frustration-limited domains model) for the description of the temperature dependence of alpha-relaxation time taualpha is considered for three typical glass-formers (propylene carbonate, ethanol and picoline). Two first functions have three free parameters. It was found that while they are in satisfactory agreement with the experimental data of taualpha(T), they fail in describing the transition from an Arrhenius-like to a non-Arrhenius behaviour. This transition is seen in the derivative analysis of taualpha(T). We argue that Vogel-Fulcher-Tammann and double activation functions should be applied and compared only at T < TA, where TA is the temperature of transition from an Arrhenius-like to a non-Arrhenius behaviour. It was shown that the four-parametric frustration-limited domains model with imbedded transition from Arrhenius to non-Arrhenius behaviour at T = T* also has no advantage in the derivative analysis, since T* is systematically different from TA in the cases considered.