The high-frequency dynamics of two strong glasses, v-GeO2 and v-ZnCl2, were studied by means of inelastic neutron scattering experiments carried out with three triple-axis spectrometers in order to selectively access either a wide kinematic region or a high-energy resolution. The experimental spectra show well-defined dispersive acoustic excitations coexisting with non-dispersive waves. A thorough analysis of the inelastic line shape of longitudinal acoustic excitations provides estimates of the damping factors, which can be compared to the results of several earlier inelastic X-ray estimates for a wide class of inorganic glasses. A striking relation is observed between the microscopic damping of phonon-like modes in these glasses well below T-g and the fragility of the supercooled liquids approaching the glass transition, thus suggesting new means of investigation of the glass transition phenomenology. (c) 2006 Elsevier B.V. All rights reserved.
Phonon-like dynamics in glasses: Coupling between damping and fragility
Bove LE;
2006
Abstract
The high-frequency dynamics of two strong glasses, v-GeO2 and v-ZnCl2, were studied by means of inelastic neutron scattering experiments carried out with three triple-axis spectrometers in order to selectively access either a wide kinematic region or a high-energy resolution. The experimental spectra show well-defined dispersive acoustic excitations coexisting with non-dispersive waves. A thorough analysis of the inelastic line shape of longitudinal acoustic excitations provides estimates of the damping factors, which can be compared to the results of several earlier inelastic X-ray estimates for a wide class of inorganic glasses. A striking relation is observed between the microscopic damping of phonon-like modes in these glasses well below T-g and the fragility of the supercooled liquids approaching the glass transition, thus suggesting new means of investigation of the glass transition phenomenology. (c) 2006 Elsevier B.V. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.