Effects of permanent densification on the vibrational density of states of vitreous silica

We present a detailed Raman scattering study of the boson peak evolution in vitreous silica as a function of density, from the normal one up to ~ 22% of densification. We show that the distribution of low frequency modes in the boson peak range does not change as a function of density, at least until the densification process starts to modify the glassy network structure from a fourfold coordinated structure into a sixfold coordinated one.