Cation vacancy and possible hydrogen positions in hydrous forsterite, Mg_<1.985>Si_<0.993>H_<0.06>O_4, synthesized at 13.5GPa and 1300℃
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The crystal structure of a single crystal of synthetic hydrous forsterite, (Mg<sub>1.985</sub>Si<sub>0.993</sub>H<sub>0.06</sub>O<sub>4</sub>), synthesized at <i>T</i> = 1300 °C and <i>P</i> = 13.5 GPa has been investigated using X-ray diffractometry and unpolarized infrared absorption spectroscopy. The data show an Mg atom occupancy of 98.6(2)% at the M(1) site and 99.9(2)% at the M(2) site, indicating that the cation vacancies predominantly occur at the M(1) site. A comparison of the calculated bond distances shows that the most probable H atom locations are at the O(2) and O(3) sites, where H may be located in association with the vacancy at the M(1) or the T site, forming hydrogen bonds between two oxygen pairs, O(3)-O(1) and O(2)-O(1), which correspond to the OH stretching vibrations at 3566 cm<sup>−1</sup> and 3612 cm<sup>−1</sup> observed in the IR spectra.
- Journal of Mineralogical and Petrological Sciences
Journal of Mineralogical and Petrological Sciences 101(5), 265-269, 2006-10-01
Japan Association of Mineralogical Sciences