Ex situ ambient pressure Raman spectra of non-densified silica (black bold solid line), sample R 12 (blue dotted line), sample B 22 (red dashed line), compared with crystalline analogs of SiO2, α cristobalite (black solid line), and coesite (red dashed and dotted line).
In situ Raman spectra from sample R 12, recorded upon decompression at 4.4 GPa (red dashes), 2.7 GPa (blue dots), and ambient pressure (black).
In situ Raman spectra from sample R 19, recorded upon decompression at 4.5 GPa (red dashes), 2.7 GPa (blue dots), and ambient pressure (black).
Main band shift as a function of applied pressure: non-densified SiO2 upon compression up to 19 GPa—thus including up to 12 GPa (full squares), SiO2 compressed up to 12 GPa upon decompression (full circles), SiO2 compressed up to 19 GPa upon decompression (full stars). Open symbols: same evolution upon decompression but after the first compression/decompression cycle up to the maximum pressure reached and a second compression up to 5 GPa. Solid lines: linear fits of the MB evolutions with pressure.
MB shift with pressure in the elastic regime. Squares: non-densified silica upon first compression.8 Circles: sample R 12, upon decompression. Stars: sample R 19, upon decompression. Full lines correspond to polynomial fits and linear fit, as guides to the eye. Inset: derivative of the polynomial fits to the corresponding MB evolutions for non-densified silica (solid line), sample R 12 (dotted line), sample R 19 (dashed line).
Brillouin frequency shift evolution in silica glass upon compression from ambient pressure up to 12 GPa (full black squares) and upon decompression from 12 GPa (open blue squares), this study: sample B 12. Brillouin frequency shift evolution in silica glass upon decompression from 15 GPa (open pink up triangles), this study: sample B 15. Tran results35 upon decompression from 10 GPa (open black down triangles), Grimsditch results1 up to 17 GPa (full green stars) and upon decompression from 17 GPa (open green stars). Compression up to 22 GPa (full red circles) and decompression from 22 GPa (open red circles), this study: sample B 22.
Evolution of with pressure for different maximum pressure reached. Black dots correspond to a maximum pressure reached of 10 GPa (Tran35), blue dashes to sample B 12 (12 GPa), purple dots dashes to sample B 15 (15 GPa), and red solid line to a maximum pressure reached of 17 GPa (Grimsditch1). Solid lines correspond to constant fits between 2 and 9 GPa of the different x%.
Evolution of HDA ratio with the maximum pressure reached: squares correspond to our results, triangle to Tran results.35 Open red stars correspond to the non-hydrostatic point of Grimsditch.1 Points at 8 GPa and at 20 GPa are retrieved from Refs. 7,24. The dashed black line is a growth fit as a guide for the eyes.
Samples description summary.
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