Vibrations in amorphous silica

• An accurate first principles calculation of structure and dynamics of amorphous silica
• The largest ab initio study of phonons in silica yet presented
• A detailed analysis of the resulting modes and their localization
• Revealing animations of the modes, of both pedagogic and research value
• New insights into the origin of the Boson peak

In this paper, we describe the vibrational properties of a realistic 648-atom model of SiO2 ([1] Tafen and Drabold, 2005). The normal modes of the model are computed with the ab initio density functional code SIESTA ([2] Soler et al., 2002). The static structure factor and the electronic density of states are in reasonable agreement with the experimental data. The vibrational density of states is analyzed by evaluating the partial density of states and localization. The vibrational modes were further investigated by calculating phase quotient and stretching character, and constructing animations of specific nodes of interest. We have obtained a low temperature specific heat in qualitative agreement with experiments, including a feature resembling the Boson peak, and the modes that give rise to this feature.