Non-Arrhenius response of glass-forming liquids

A Gaussian size distribution of independently relaxing domains is used to model the response of various glass-forming liquids. With a single temperature-dependent parameter, the model accurately characterizes the observed dielectric susceptibility of salol and glycerol [P. K. Dixon et al., Phys. Rev. Lett. 65, 1108 (1990); N. Menon et al., J. Non-Cryst. Solids 141, 61 (1992)] over more than 13 orders of magnitude in frequency. The quality and range of these data allow quantitative confirmation of all assumptions of the model. As a function of temperature, the model gives excellent agreement with observed asymptotic relaxation rates (${\mathit{w}}_{\mathrm{\infty }}$) via [ln(l/${\mathit{w}}_{\mathrm{\infty }}$)-ln(1/${\mathit{w}}_0$)]∝s¯, where s¯ is a temperature-dependent average domain size, and ${\mathit{w}}_0$ a constant intrinsic relaxation rate. Thus, the model provides a physical explanation for non-Arrhenius primary response, without resorting to the three adjustable parameters of the Vogel-Tammann-Fulcher law.