Acoustic nature of the boson peak in vitreous silica

New temperature-dependent inelastic X-ray scattering (IXS) and Raman scattering (RS) data are compared with each other and with existing inelastic neutron scattering (INS) data in vitreous silica, in the 300-1775 K region. The IXS data show collective propagating excitations up to Q = 3.5 nm −1 . The temperature behaviour of the excitations at Q = 1.6 nm −1 matches that of the boson peak found in INS and RS. This supports the fact that the acoustic origin of the excess of vibrational states gives rise to the boson peak in this glass.