Determination of hydrogen site and occupancy in hydrous Mg 2SiO4 spinel by single-crystal neutron diffraction
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.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division
- Grant/Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1625829
- Journal Information:
- Acta Crystallographica. Section B, Structural Science, Crystal Engineering and Materials (Online), Vol. 74, Issue 1; ISSN 2052-5206
- Publisher:
- International Union of CrystallographyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Quasielastic neutron scattering of brucite to analyse hydrogen transport on the atomic scale
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journal | October 2018 |
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