Neutron Scattering Study of Lattice Dynamics in CuBr Part I. Phonon Dispersion Relations

Phonon dispersion relations of CuBr having zincblende-type structure were measured by the neutron inelastic scattering technique with a triple-axis spectrometer. The dispersion curves measured at 77 K were well described by the shell model with 14 parameters which has been successfully applied to explain the data for GaAs, GaP and InSb. The elastic constants were obtained both from sound velocities estimated from the initial slopes of acoustic phonon dispersion curves and from the shell-model-fit. The optical phonon energies at the zone center are in good agreement with the Raman scattering data. The temperature dependence of phonon scattering was also measured. It was found that the phonon energies as well as the shape of phonon peaks varied considerably with temperature, suggesting that the effect of anharmonicity is remarkable in CuBr even at room temperature.