Phonons and their interactions

Abstract The power of neutron scattering methods to probe the dynamical behaviour of atoms and molecules in solids is illustrated by several examples taken from the now enormous literature on phonons, related excitations and phonon interactions in perfect and not so perfect crystals. The seminal role played by the soft mode concept is stressed. Although references are made to early investigations in some areas, the emphasis is on the last decade of research. Nearly all of this research has been carried out at steady state reactor sources with triple axis crystal spectrometers.