Abstract
The space group and hydrogen positions of δ-(Al0.84Mg0.07Si0.09)OOH are investigated using a single crystal synthesized using a multi-anvil apparatus under conditions of 1000 °C and 21 GPa. The space group determined by single-crystal X-ray diffraction is to Pnn2, with unit-cell parameters of a=4.6975(8) Å, b= 4.2060(6) Å, c=2.8327(4) Å, and V=55.97(1) Å3. Partial occupancy of the Al site by Mg and Si suggests the possibility of a limited solid solution between δ-AlOOH, stishovite, and a hypothetical CaCl2-type Mg(OH)2 that is 16% denser than brucite. Difference-Fourier maps reveal two small but significant Fourier peaks attributable to hydrogen atoms. Atomic distances and angles around the first peak indicate a hydrogen bond with O···O distances of 2.511 Å, while those around the second peak are suggestive of a bifurcated hydrogen bond with O···O distances of 2.743 and 2.743 Å.
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Acknowledgments
This work was partly supported by Grant-in-Aid for Scientific Research (no. 13304041) from the Japan Society for the Promotion of Science.
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Kudoh, Y., Kuribayashi, T., Suzuki, A. et al. Space group and hydrogen sites of δ-AlOOH and implications for a hypothetical high-pressure form of Mg(OH)2. Phys Chem Minerals 31, 360–364 (2004). https://doi.org/10.1007/s00269-004-0404-0
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DOI: https://doi.org/10.1007/s00269-004-0404-0