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Figure 1
(a) Thermogravimetry results of DHMS phase E [Mg3−0.5xSixH6−3xO6] and brucite [Mg(OH)2] measured at ambient pressure using Rigaku Thermo plus EV02. The former structure retains most of its hydrogen at around 900 K, while the latter retains it at around 600 K. We consider that the difference in dehydration temperatures between these minerals is related to the difference in their hydrogen bonding strengths. (b) Two equally plausible hydrogen site models that have been adopted so far for DHMS phase E (Tomioka et al., 2016BB24). Each corner of the octahedra is made of an oxygen anion (not shown). In the normal O—D model, the dipole is parallel to the c axis and normal to the MgO6 octahedral layers. In the tilted O—D model, the dipole is tilted from the c axis. The crystallographic illustrations were created using the software VESTA3 (Momma & Izumi, 2011BB8).

IUCrJ
Volume 7| Part 3| May 2020| Pages 370-374
ISSN: 2052-2525
https://doi.org/10.1107/S2052252520003036