Abstract

In this work we will face the problem of the vibrational properties of glasses focusing on the origin and nature of the boson peak (BP). This feature is an universal characteristic of glasses and a fingerprint of the presence of disorder. Two samples have been chosen for this study. The first is permanently densified vitreous SiO$_2$. Permanent densification has been exploited to tune the glassy properties focusing on their evolution. The second sample is a silicon-selenium glass whose low sound velocity allows a detailed study of its dynamics by means of neutron inelastic scattering.