Raman, Brillouin light, and x-ray scattering measurements have been carried out to characterize the low-frequency vibrational dynamics of the SiO(2) glass as function of its density. The obtained results demonstrate that while the distribution of the low-frequency states in the boson peak range is conserved under densification, these modes do not shift as a function of density as the acoustic modes do. The clear difference between the behavior of the vibrational states in the Boson peak range and that of the acoustic modes, could be explained considering the contribution of specific nonacoustic modes (tetrahedra rotation

Inelastic neutron, light, and x-ray scattering are used to investigate the vibrational density of states (VDOS) and the elastic properties of a sodium silicate glass as a function of temperature. The elastic moduli show the frequency and temperature dependence typical of anharmonic effects. The measured VDOS spectra, up to and including the excess vibrational density at the boson peak, scale with the Debye level only if this is calculated from the high-frequency values of the elastic constants. This emphasizes that conclusions on the relation between VDOS and elastic properties can be drawn only if anharmonic and relaxational effects are properly taken into account.

A specific and widely accepted protocol for quality controls in DWI is still lacking. The DWI quality assurance protocol proposed in this study can be applied in order to assess the reliability of DWI-derived indices before tackling single- as well as multicenter studies.

Vitreous GeO(2), one of the main prototypes of strong glasses, was densified at several pressures up to 6 GPa, achieving more than 20% of densification. The density dependence of the vibrational density of states and of the low temperature properties of these glasses was investigated by means of inelastic neutron scattering and calorimetric measurements. With increasing density, both the boson peak and the bump in c(p)/T(3) versus T plot exhibit variations which are stronger than the elastic medium expectation. If one reduces the measured spectra to a common master curve, one finds that this is only possible for the densified samples; the first densification step has an additional effect, similar to other cases in the literature. Nevertheless, the existence of a master curve for the three densified samples proves that the total number of excess modes remains constant on further densification. The experimental data are discussed in the framework of different theoretical models.