Vibrational dynamics of densified silica glasses studies by inelastic x-ray scattering

An anomaly present in the vibrational density of states (VDOS), g(E), at energies of few meV has attracted much interest due to its universal occurrence in glasses. This anomaly is best evidenced as a broad bump, known as boson peak (BP), appearing in the reduced density of states g(E)/E2 over the Debye, elastic continuum prediction in an energy range where the Debye model still works reasonably well for the corresponding crystals.
Silica glasses with densities between 2.20 and 2.67 g/cm3 have been prepared pressurizing silica at high-pressure high-temperature conditions in a large volume press. The corresponding VDOS spectra have been measured using nuclear resonant analysis of inelastic X-ray scattering. The effect of densification on the BP of silica has then been obtained, indicating a continuous transition from a VDOS spectrum similar to that of α-cristobalite to one similar to that of α-quartz.