Dynamic structure factor of vitreous germania

Abstract

Inelastic neutron scattering experiments have been performed in melt-quenched vitreous Germania, v-GeO 2, at room temperature. Coherence effects have been observed in the dynamical structure factor over the collective excitations energy range. Indeed, because of the relatively low velocity of sound of this system (3600 m/s), the linear low- q region of the ( q, ω) dispersion relationship was accessible to the neutron experiment. The observed effects are consistent with the acoustic-phonon dispersion curves of the corresponding crystal, thus supporting the hypothesis that, also in glassy systems, longitudinal and transverse acoustic branches can be still defined, even if they are broader than in crystals, due to topological disorder.