Order and disorder in high-temperature long-wave acoustics (I): dielectrics, semiconductors, and conductors

The linear long-wave approximation is used to analyze the classical interaction between elastic waves and local disorder in dielectric, semiconducting, and metallic crystals. It is shown that carriers of thermal and nonthermal disorder provide significantly different contributions to the acoustic parameters of crystals such as the velocity of sound and the sound attenuation coefficient. The effect of direct and indirect interactions between elastic waves and the ensemble of carriers of disorder on the attenuation of sound is examined. In the former case, deformation by the wave modifies the motion of the carriers of disorder themselves, whereas in the latter case the elastic wave interacts with quasiparticles in the crystal, and the presence of disorder is seen as a change in the character of motion of these quasiparticles. The effects of high concentrations of carriers of disorder produced by melting one of the sublattices of superionic crystals are also described.