A paper led by our alumnus Dr. Mori on the elastic wave velocity of hydrous post-stishovite under ultrahigh pressures has been published in American Mineralogist.
Dense SiO2 phases such as stishovite and post-stishovite are known to retain relatively large amounts of water in their crystal structures under lower-mantle conditions. In this study, we directly measured the shear-wave velocity of hydrous post-stishovite at pressures of up to 100 GPa by Brillouin spectroscopy using a diamond-anvil cell. The results show that hydrous post-stishovite has a lower shear-wave velocity than its anhydrous counterpart, although the difference gradually diminishes with increasing pressure. This indicates that water softens SiO2 at lower pressures but enhances its pressure-induced stiffening at higher pressures.
Mori Y., Murakami M., Yoshino T., and Kagi H. (2026) Ultrahigh-pressure elasticity of dense hydrous SiO2. American Mineralogist, 111, 1025-1035.