Temperature effects on lattice vibrations in germanium

Abstract

Frequencies of selected normal modes of germanium at temperature of 100°K and (roughly) 700°K were determined using neutron spectrometry. The results (Table 1) show that the frequencies at 700°K are uniformly lower than those at 100°K by 4.5 (± 0.6)%. The various harmonic force constants thus appear to have a common specific dependence on the temperature, probably through a general "softening" of the electronic structure. No energy broadening of the neutron groups was observed; this may simply be an aspect of the smallness of the anharmonicity in germanium.