TOPOLOGICAL MODEL FOR VISCOUS RELAXATION IN CRITICAL OXIDE MIXTURES.

A topological model is formulated to analyze results from supercritical viscosity and ultrasonic relaxation measurements in molten oxide glasses. The model assumes that a distribution of relaxation times can be related to a distribution of environments and shows that the change in width of the distribution of relaxation times directly depends upon changes in the local composition. These changes in local composition are formulated in terms of the temperature dependent mean square compositioon fluctuation which appears above the liquid-liquid critical point. A final equation is then obtained which describes the change in the width of the relaxation time spectrum in terms of a parameter defined as the ratio of the range of structural forces to the supercritical correlation length. The final equation is compared to the results from ultrasonic spectroscopy, and is qualitatively extended to non-critical oxide systems. Author