Neutron diffraction study of hydrous ringwoodite

Abstract

Ringwoodite is one of the potential water reservoirs in the deep mantle. Its crystal structure has been well refined by X-ray diffraction studies; however, hydrogen positions in the ringwoodite structure are still not clear due to very low X-ray sensitivity of hydrogen atom. In order to determine positions and site occupancies of hydrogen, homogenous powder of deuterated hydrous ringwoodite were synthesized in large volume by newly developed cell assembly at ~20GPa and 1000-1300°C. A powder neutron diffraction pattern was successfully obtained from ~65 mg of the sample and the obtained diffraction pattern is now under Rietveld refinement.