Phonon Density of States in Germanium at 80 K Measured by Neutron Spectrometry

Abstract

More than 500 frequencies of phonons with reduced wave vectors evenly distributed over an irreducible section of the first Brillouin zone have been measured in germanium at 80 K with a neutron crystal spectrometer. The phonon density of states was calculated from the data with an improved sampling technique. Comparisons between thermodynamic quantities derived from calorimetric data and from the present spectrum reveal an excellent agreement. A critical-point scheme determined by use of a method originating from Phillips is also presented. The scheme properly satisfies the Morse relations and other topological conditions, and most of the van Hove singularities expected are clearly displayed in the spectrum.