Crystal structure of sibirskite (CaHBO_3) by Monte Carlo simulation and Rietveld refinement
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The crystal structure of sibirskite (CaHBO<sub>3</sub>) was solved by the Monte Carlo simulation using powder X-ray diffraction data and confirmed by the Rietveld refinement. The mineral sibirskite is monoclinic with space group <i>P</i>2<sub>1</sub>/<i>a</i> and cell constants of <i>a</i> = 8.643(6), <i>b</i> = 9.523(2), <i>c</i> = 3.567(3) Å, and <i>β</i> = 119.23(3)°. The unit cell consists of independent atoms such as calcium, boron, hydrogen, and three oxygen atoms. The calcium atom is surrounded by six oxygen atoms in an octahedral coordination, and a symmetrical pair of edge-shared CaO<sub>6</sub> octahedra forming a double chain elongates the crystallographic <i><b>c</b></i> axis. The CaO<sub>6</sub> double chains are not directly connected to each other. The BO<sub>3</sub> triangles are linked to one vertical and two shared oxygen atoms in three CaO<sub>6</sub> double chains to form the sibirskite structure. Sibirskite is isostructural with nahcolite (NaHCO<sub>3</sub>), which consists of NaO<sub>6</sub> double chains and CO<sub>3</sub> triangles.
- Journal of Mineralogical and Petrological Sciences
Journal of Mineralogical and Petrological Sciences 103(2), 156-160, 2008-04-01
Japan Association of Mineralogical Sciences