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- Title
Determination of hydrogen site and occupancy in hydrous Mg<sub>2</sub>SiO<sub>4</sub> spinel by single‐crystal neutron diffraction.
- Authors
Purevjav, Narangoo; Okuchi, Takuo; Wang, Xiaoping; Hoffmann, Christina; Tomioka, Naotaka
- Abstract
Ringwoodite [(Mg,Fe2+)2SiO4 spinel] has been considered as one of the most important host minerals of water in the Earth's deep mantle. Its extensive hydration was observed in high‐pressure synthesis experiments and also by its natural occurrence. Water can dissolve into ringwoodite as structurally bound hydrogen cations by substituting other cations, although the hydrogen site and its occupancy remain unclear. In this study, neutron time‐of‐flight single‐crystal Laue diffraction analysis was carried out for synthetic hydrous ringwoodite. Hydrogen cations were found only in the sites in MgO6 octahedra in the ringwoodite structure, which compensated the reduced occupancies of both magnesium and silicon cations. The refined cation occupancies suggest that the most plausible hydration mechanism is that three hydrogen cations simultaneously occupy an MgO6 octahedron, whereas four such hydrogenated octahedra surround a vacant SiO4 tetrahedron.
- Subjects
MAGNESIUM; SILICON
- Publication
Acta Crystallographica Section B: Structural Science, Crystal Engineering & Materials, 2018, Vol 74, Issue 1, p115
- ISSN
2052-5192
- Publication type
Article
- DOI
10.1107/S2052520618000616