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 (w(infinity)) via [ln(/w(infinity))-ln(1/w0)] is-proportional-to sBAR, where sBAR is a temperature-dependent average domain size, and w0 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.