Structural and dynamical consequences of density variation in vitreous silica

Abstract

We present structural and dynamical results of molecular dynamics simulation of vitreous silica undergoing a hydrostatic compression and decompression cycle at room temperature. Structural results as a function of density compare fairly well with experiments as well as with the longitudinal and transverse sound velocity pressure dependence. A shift of the boson peak (BP) toward higher energies and its simultaneous weakening is observed as in experiments. A detailed study of the dispersion of the glass vibration is presented at several densities and for the densified state. Evidence of phonon-like character with two distinct pseudo-periods is shown for longitudinal and transverse dynamics. The relationship between the BP vibrations and the correlation length scale indicated by the first sharp diffraction peak is discussed.