Vibrational dynamic of ‘strong’ glasses: the case of v-SiO2 and v-GeO2

The vibrational dynamic of vitreous germania (v-GeO2) with respect to that of vitreous silica (v-SiO2) has been investigated by means of several inelastic and elastic scattering experiments. These amorphous systems belong to the large family of continuous random network forming glasses. In spite of their topological similarity, some dynamical differences have been singled out. We present experimental data on light Raman scattering at room temperature as well as new elastic and inelastic neutron scattering. Transversal-acoustic character of the vibrations responsible for the density of states excess in the Boson peak energy range is found.