Transport in Random Structures Localized vibrational states above a mobility energy are thought to characterize amorphous and glassy structures. Lattice anharmonicity can connect extended and localized states, affecting dispersion and lifetimes for both species. These effects are being used to extract transport properties for a wide variety of random materials. The vibrational lifetimes of localized excitations of high energy are found to be anomalously long at low temperatures for amorphous and glassy structures. The lifetimes are found to increase with increasing vibrational energy, quite opposite to that found in crystalline materials.
Calculations are underway to determine vibrational lifetimes in a variety of random structures.
Comparison with experiment is excellent, suggesting that this approach may have very general applicability.