REALISTIC MODEL-CALCULATIONS BASED ON THE KUBO THEORY FOR THE THERMAL-CONDUCTIVITY OF AMORPHOUS INSULATORS

The thermal conductivity of models of amorphous silicon and vitreous s ilica are discussed. In previous work on amorphous silicon, 216- and 1 000-atom models were studied within the Kubo theory and the harmonic a pproximation using the Stillinger-Weber potential and good agreement w ith the experimental high-temperature apparent saturation value was ob tained. In order to test the model dependence of such results we perfo rmed calculations for models based on the Keating potential. The Keati ng model apparently gives much less force-constant disorder than does the Stillinger-Weber model, as evident from the N dependence and the f requency range of localized states. We also present results of calcula tions for vitreous silica based on the Feuston-Garofalini model that w e relaxed, using their potential, to zero pressure. The results for vi treous silica are in fair agreement with experiment at temperatures ab ove 100 K which corresponds to the lowest normal-mode frequency contai ned within the model.