Amorphous silica from the Rigid Unit Mode approach

We apply the Rigid Unit Mode model, which was initially developed for cryst alline silicates, to the study of the flexibility of silica glass. Using a density-of-states approach we show that silica glass has the same flexibili ty against infinitesimal displacements of crystalline phases. Molecular dyn amics simulations also show that parts of the silica structure are able to undergo large spontaneous changes through reorientations of the SiO4 tetrah edra with no energy cost.