Structural evolutions of CaSiO3 and CaMgSi2O6 metasilicate glasses by static compression

We determined the structural changes in CaSiO3 and CaMgSi2O6 glasses recovered from high pressure and temperature conditions (up to 7.5 GPa and 500 °C) using X-ray diffraction, Raman, infrared and X-ray emission spectroscopy. Densities of the metasilicate glasses increase with applied pressure at high temperature; CaMgSi2O6 glass is more compressed than CaSiO3 glass when recovered from 7.5 GPa and 500 °C. We propose a mechanism for densification of these glasses, that is mainly due to the compaction in medium-range scale (i.e. decrease in cluster size of SiO4 anionic units with Ca, Mg polyhedra). Reduction of Si–O–Si bond angle is very small in the recovered CaSiO3 and CaMgSi2O6 glasses, as previously suggested.