RANDOM-WALK APPROACH TO DYNAMIC AND THERMODYNAMIC PROPERTIES OF SUPERCOOLED MELTS .2. COUPLING OF STRUCTURAL UNITS AND SUSCEPTIBILITY SPECTRA

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 narrowi ng of the distribution function for the energies of structural units. As the temperature approaches a critical value T-K the ordered cluster s expand, the distribution function approaches a delta-function, and t he configurational entropy vanishes. This allows to identify the tempe rature T-K as the Kauzmann temperature. The model is also applied to t he calculation of susceptibility spectra. The results are in quantitat ive agreement with existing experimental data.