Single-crystal structures of high-pressure phases FeOOH, FeOOD, and GaOOH

The structures of the ɛ-FeOOH, ɛ-FeOOD, and β-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 Xcalibur CCD and CAD-4F diffractometers. The calculations are carried out in space group P 2 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°. In the same crystals, the merohedral twinning is characterized by the rotation around the c axis through an angle of 180°. The alternation of these twin domains in the bulk of the crystal determines the corresponding disordering of the hydrogen positions.