Dispersion Relations for Phonons in KCl at 80 and 300°K

Phonon dispersion relations in KCl at 80°K have been determined using inelastic neutron scattering. The measurements have been performed mainly in the symmetry directions [100], [110], and [111], but also at some other points in the reciprocal space. More than one third of the phonons in all branches were also studied at 300°K in order to obtain and estimate of the temperature dependence of their frequencies. A comparison is made with dispersion curves calculated by Nüsslein and Schröder for their “breathing shell” variant of the shell model for ionic crystals. The agreement for the dispersion curves is quite satisfactory in the most cases.