Observation of pressure-induced phase transition of -AlOOH by using single-crystal synchrotron X-ray diffraction method

Kuribayashi, Takahiro*; Sano, Asami   ; Nagase, Toshiro*

Pressure-induced phase transition of -AlOOH was confirmed between 6.1 and 8.2 GPa by using a single-crystal synchrotron X-ray diffraction method. The phase transition is reversible and unquenchable. The space group of the post-transition phase should be or 2 to satisfy the systematic absence rule. Crystal structure refinements of the post-transition phase conducted for the three models (, 2, and 2) indicate that the space group of the post-transition phase is . The O-O distance of hydrogen bond in the post-transition phase at 8.2 GPa is 2.439(6) and is significantly longer than the predicted distance (2.366 ) of the hydrogen bond symmetrization in -AlOOH. The H distribution in the post-transition phase would display a fully disordered hydrogen bond pattern.