A theory of phonons in amorphous systems and liquids

Abstract A successful theory for electronic states in amorphous solids, based on a novel approach to the description of structural disorder, is extended to calculate the phonon spectral distribution function. It will be shown that both the structural model, based on correlations between neighbourhoods, and the approximation procedures, based on the response to an infinitesimal applied field, are capable of systematic improvement. It will also be demonstrated that this development allows earlier work by Hubbard and Beeby on collective excitations to be extended into the long wavelength, i.e. hydrodynamic, regime.