Phonons in Amorphous Solids

Abstract

Lattice vibrations, or phonons, in crystalline solids have been studied since the beginning of the century1. Until about 15 years ago they were seen experimentally rather indirectly but since then, inelastic neutron scattering has made the direct measurement of phonon dispersion curves almost routine.2 The phonons in a solid are a basic ingredient in understanding such things as specific heat, melting, ferroelectricity and superconductivity. Phonons also occur in amorphous solids or glasses and play similar roles in determining their physical properties. It is therefore important to understand them from a fundamental, i.e. microscopic, viewpoint. It is only recently with the advent of good experimental data on simple systems that this has been undertaken and the subject is still in its infancy. In these lectures we will attempt to outline the progress that has been made and point out some of the problems that still remain.