Phonon spectra of hexagonal potassium tungsten bronze (K0,33WO3)

Abstract
The phonon dispersion curves of hexagonal potassium tungsten bronze have been investigated through inelastic scattering of thermal neutrons. The low frequency modes along the [ξ; 0,0|, [ξ ξ, 0] and [0,0, ξ] symmetry directions have been determined at room temperature. Of particular interest is the occurrence of relatively flat transverse acoustic modes near 1.3 Thz. These modes would seem to be responsible for the dramatic departure from Debye-like behavior exhibited in a crude evaluation of the phonon density of states. The resulting maximum in g(v)/v 2 agrees well with the frequency of an Einstein mode postulated by Bevolo et al. 1 as a possible explanation for anomalies in the heat capacity.