Pressure-induced densification of vitreous silica: Insight from elastic properties
Coralie Weigel, Marouane Mebarki, Sébastien Clément, René Vacher, Marie Foret, and Benoit Rufflé *
Laboratoire Charles Coulomb (L2C), University of Montpellier, CNRS, Montpellier, France
(Received 19 December 2018; published 3 September 2019)

In situ high-pressure Brillouin light scattering experiments along loading-unloading paths are used to investigate the compressibility of vitreous silica. Below 9 GPA, the equation of state obtained from the sound velocities corrected for dispersion agrees with volume measurements. Conversely, huge anelastic effects are observed in the range 10–60 GPa, unveiling the reversible transformation from the fourfold-coordinated structure to the sixfold one. The associated density changes correlate with the average Si coordination number.
Decompression curves from above 20 GPa reveal abrupt backward coordination changes around 10–15 GPa and
significant hysteresis. Contrary to common wisdom, the residual densification of the recovered silica samples
can be figured out from changes in elastic properties along pressure cycles, ruling out a plastic description of the
latter process.