Single-Crystal Structures of High-Pressure Phases FeOOH, FeOOD, and GaOOH

The structures of the epsilon-FeOOH, epsilon-FeOOD, and beta-GaOOH phases, which belong to the InOOH structure type (the distorted TiO(2) structure type), are determined using single-crystal X-ray diffraction analysis. The measurements are performed on X calibur CCD and CAD-4F diffractometers. The calculations are carried out in space group P2(1)nm with the JANA2000 program. The crystals are twinned and form aggregates related by the rotation around the b axis through an angle close to 62 degrees. In the same crystals, the merohedral twinning is characterized by the rotation around the c axis through an angle of 180 degrees. The alternation of these twin domains in the bulk of the crystal determines the corresponding disordering of the hydrogen positions.