High Pressure Phase Transition in Groutite, MnO(OH)

Groutite, -MnO(OH), is a mineral that belongs to the diaspore group.We used X-ray synchrotron radiation in the pressure range from 0.65(6) GPa to 39.85(8) GPa to collect diffraction data for three single crystals of groutite placed in a diamond anvil cell.Groutite is orthorhombic, space group Pbnm.Analysis of the reciprocal lattice planes and the intensities of the measured reflections revealed that above 30 GPa, a phase transformation begins in the structure.This transition is gradual, with observable changes in the intensity of specific reflections, particularly those that are forbidden in the Cmcm space group.Although we see significant decreases in the intensities of these reflections, many of them still have intensities significantly greater than zero after the beginning of transformation.This is accompanied by a smooth, continuous shrinkage in the unit cell volume, symmetrization of hydrogen