Lattice Dynamics of Potassium Chloride

Abstract

Phonon dispersion curves along the $\left[00\mathrm{}\zeta \right]$, $\left[0\mathrm{}\zeta 1\right]$, $\left[0\mathrm{}\zeta \zeta \right]$, and $\left[\zeta \zeta \zeta \right]$ directions in KCl at 115°K have been measured by inelastic scattering of slow neutrons using the McMaster University triple-axis spectrometer at Chalk River. Various versions of the shell model have been fitted to the measurements. They are also compared with Kucher's predictions and with the results of Schröder's breathing-shell model. Several quantities are calculated using the best-fit shell model. The main features of the frequency distribution function do not, in general, occur at the frequencies of the symmetry points $X$ and $L$. The most prominent peak in the frequency distribution is at 155 ${\mathrm{cm}}^{-1\mathrm{}}$. It agrees with the strongest peak in the Raman spectrum of KCl. The Debye temperature, the Debye-Waller factor, and the inelastic structure factor are also calculated.