Phonon spectrum of CuCl at 4.2K and its temperature dependence

Abstract

The phonon dispersion curves of cuprous chloride have been determined at 4.2K by inelastic neutron scattering. The curves are very similar to those for the isomorphous CuBr and CuI. They are analysed within the shell model formalism, which permits the calculation of derived quantities such as one- and two-phonon densities of states, Debye temperature and amplitudes in the Debye-Waller factor for the individual ion. The frequencies of the phonons are not very temperature dependent: 6% renormalisation for some optic modes between 4.2K and 300K, but the peak intensity or the visibility is rapidly decreasing with increasing temperature, indicating the strong anharmonicity of CuCl.