Meeting room "Glova", 4 floor, Integrated Research Building
Abstract
Because of the extraordinary high pressure stability, d-AlOOH, a high pressure phase of diaspore and boehmite, is attracted particular attention in geophysics as a possible carrier and reservoir of water (OH-) into the deep Earth's interior. So far we have investigated and reported the structure, vibrational and elastic properties of this phase. Recently, we found a new high-pressure phase of AlOOH stabilizing at ~170 GPa by first principles density functional calculations. The structure predicted has a cubic pyrite-type AlO2 framework with interstitial H atoms forming symmetric hydrogen bonds, whose symmetry is assigned to the space group Pa3 (No. 205). The predicted d-AlOOH to pyrite-type phase sequence is quite analogous to a recent theoretical and experimental discovery of the high-pressure phase evolution in InOOH, but the transition pressure is much greater in AlOOH. Interestingly it also invokes high-pressure phase relationships in dioxide compounds such as SiO2. Relative enthalpies also indicate that the dissociation of this phase into a Cmcm phase of Al2O3 plus Ice X likely finally occurs at a quite high pressure of 300 GPa. The present results suggest that AlOOH has an unexpectedly wide stability range in pressure compared to common hydrous materials.
For inquiry：Taku Tsuchiya TEL:（089）927-8198
E-mail takut@sci.ehime-u.ac.jp
