Random-Walk Approach to Dynamic and Thermodynamic Properties of Supercooled Melts. 2. Coupling of Structural Units and Susceptibility Spectra

Abstract

The random-walk model of structural dynamics in supercooled liquids is generalized to account for long-range cooperative phenomena. Coupling of structural units within ordered clusters is shown to cause narrowing of the distribution function for the energies of structural units. As the temperature approaches a critical value TK the ordered clusters expand, the distribution function approaches a δ-function, and the configurational entropy vanishes. This allows to identify the temperature TK as the Kauzmann temperature. The model is also applied to the calculation of susceptibility spectra. The results are in quantitative agreement with existing experimental data.