Neutron scattering studies of vitreous germania

To assess the source of the excess of states, compared to the predictions of the Debye theory, inelastic neutron scattering experiments have been performed, at room temperature in melt-quenched vitreous germania. Coherence effects in the dynamics structure factor, S(q,ω), in the Boson peak energy range have been observed: the Boson peak maximum shifts as a function of the exchanged wave vector. These effects are consistent with average acoustic–phonon dispersion curves, which are similar in structure to the dispersion curves found in crystals but much broadened by the topological disorder.