ON THE THERMALLY ACTIVATED STRUCTURAL RELAXATION IN GLASSES

The asymmetric double-well potential model for thermally activated structural relaxation of Gilroy and Phillips is re-examined. Analytical expressions for the attenuation and the velocity variation of acoustic waves, valid on a large range of temperature and frequency, are found. An application to a-SiO2 shows that this model using a constant distribution of asymmetries is no longer valid for T greater-than-or-similar-to 150 K. A refinement of the model is obtained by considering a Gaussian distribution of asymmetries. Good agreement is obtained in fitting ultrasonic results.