Density hardening plasticity and mechanical aging of silica glass under   pressure: A Raman spectroscopic study
  In addition of a flow, plastic deformation of structural glasses (in particular amorphous silica) is characterized by a permanent densification. Raman spectroscopic estimators are shown to give a full account of the plastic behavior of silica under pressure. While the permanent densification of silica has been widely discussed in terms of amorphous-amorphous transition, from a plasticity point of view, the evolution of the residual densification with the maximum pressure of a pressure cycle can be discussed as a density hardening phenomenon. In the framework of such a mechanical aging effect, we propose that the glass structure could be labelled by the maximum pressure experienced by the glass and that the saturation of densification could be associated with the densest packing of tetrahedra only linked by their vertices. 
Damien Vandembroucq (SVI, PMMH), Thierry Deschamps (LPCML), Camille   Coussa (LPCML), Antoine Perriot (SVI), Etienne Barthel...