Single-exponential activation behavior behind the super-Arrhenius relaxations in glass-forming liquids

Abstract

The reported relaxation time for several typical glass-forming liquids was analyzed by using a kinetic model for liquids which invoked a new kind of atomic cooperativity--thermodynamic cooperativity. The broadly studied 'cooperative length' was recognized as the kinetic cooperativity. Both cooperativities were conveniently quantified from the measured relaxation data. A single-exponential activation behavior was uncovered behind the super-Arrhenius relaxations for the liquids investigated. Hence the mesostructure of these liquids and the atomic mechanism of the glass transition became clearer.

Extracting energy and structure properties of glass-forming liquids from structural relaxation time

“…This fact, as observed by Macedo et al in B 2 O 3 [42] and 2Ca(NO 3 ) 2 -3KNO 3 (CKN) [18,19], by Laughlin and Uhlmann [31] and by Hansen et al [38] in several simple organic liquids, seems a general liquid feature. Theoretically, the kinetic liquid model used in this work has, in accord with experimental observations, captured the high and low temperature Arrhenius behaviors in the structural relaxation of glass-forming liquids [35].…”

“…As another example, the measured structural relaxation times of glycerol [36,[43][44][45][46][47] are compiled and fitted in figure 2. It is seen that the data read [35] from [43] show acceptable agreement with those uploaded in [36]. The data for glycerol were found difficult to fit and various possibilities in fitting have been tried.…”

“…In [35] it was shown that the structural relaxation time of glass-forming liquids in a wide temperature range may be fitted by the following two equations with four parameters:…”

“…In a previous work [35], a possible microscopic reason for the super-Arrhenius structural relaxation was proposed on the basis of a kinetic liquid model. By using this liquid model, the structural relaxation times of five typical glass-forming liquids were reasonably fitted in a wide temperature range with four physically clear parameters, namely, a pre-exponential factor, the enthalpy, entropy, and the cooperativity in structural relaxation.…”

“…In this work, efforts are made to apply the kinetic liquid model to as many as 26 different glass-forming liquids, including most of the well-studied materials, for a comprehensive examination of the analysis presented in [35]. Critical evaluations are given to the compiled structural relaxation data.…”