Phonons in cadmium at 80K

Abstract

The phonon spectrum of cadmium has been measured using the inelastic neutron scattering technique at 80K. Besides the usual dispersion curves for symmetry directions, a number of interesting features of the spectrum have been studied in detail. They include the splitting of the branches at the point K, accidental degeneracy of branches with the same symmetry, the behaviour of the low-frequency transverse modes in non-symmetry directions and the effect of temperature on the dispersion of these modes. The results are compared with calculations using a local model potential of the Abarenkov-Heine type and taking into account third-order terms in the potential. The model reproduces the phonon spectrum in general, but proves to be inadequate to describe the finer details.