High-pressure structural transformation ofSiO2glass up to 100 GPa

Abstract

We have conducted structure measurements of ${\text{SiO}}_{2}$ glass under high pressure up to 100 GPa by an energy-dispersive x-ray diffraction method with synchrotron white x rays. X-ray diffraction data indicate that ${\text{SiO}}_{2}$ glass transforms from a fourfold- to a sixfold-coordinated structure at pressures between 20 and 35 GPa, and then behaves as an amorphous polymorph having a sixfold-coordinated structure at least up to 100 GPa. These results are consistent with those of density measurements by an x-ray absorption method with monochromatic x rays, except for the slight difference in the pressure range where the transformation from a fourfold- to a sixfold-coordinated structure is completed. They are also mostly consistent with those of structure measurements by an x-ray diffraction method with monochromatic x rays but some aspects are quantitatively different. It is presumed that the irradiation of white x rays may have relaxed the structure and deviatoric stresses of ${\text{SiO}}_{2}$ glass in this study.