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Abstract <p>The anthropogenic calcium fluorosilicate “kutyukhinite” Ca<sub>5</sub>[SiO<sub>4</sub>]<sub>2</sub>F<sub>2</sub> from burnt dumps of the Chelyabinsk coal basin has been studied by single crystal and powder X-ray diffraction analyses in a wide temperature range. “Kutyukhinite” (<i>P</i>2<sub>1</sub>/<i>a</i>, <i>a</i> = 11.4985(4) Å, <i>b</i> = 5.0535(2) Å, <i>c</i> = 8.7848(3) Å, β = 109.008(4)°, <i>V</i> = 482.63(3) Å<sup>3</sup>, <i>R</i><sub>1</sub> = 0.0183) is an anthropogenic analogue of kumtyubeite, which belongs to the structural type of chondrodite. The empirical formula of “kutyukhinite” is Ca<sub>5.02</sub>[Si<sub>1.99</sub>O<sub>7.98</sub>]F<sub>2.04</sub>. Upon heating, its crystal structure expands anisotropically, with the direction of maximum thermal expansion close to the [100] direction. The relative change in bond lengths in silicon–oxygen tetrahedra with increasing temperature (27–927 °C) is less than 0.6%, which is within the margin of error. At the same time, the relative increase in the average bond length 〈Ca–O〉 varies from 1% (〈Ca1–O〉) to 1.5% (〈Ca3–O〉). The largest relative change of &#xa0;2% was found for the average bond length 〈Ca3–F1〉.</p>

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Calcium Fluorosilicate Ca5[SiO4]2F2 from Burnt Dumps of the Chelyabinsk Coal Basin (South Urals): Crystal Chemistry, Spectroscopy, Thermal Behavior

  • 期刊论文

  • 发表日期：

    2025年6月1日

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  • A. S. Brazhnikova,
  • A. A. Zolotarev,
  • M. S. Avdontceva,
  • S. V. Krivovichev,
  • M. G. Krzhizhanovskaya,
  • V. N. Bocharov,
  • N. S. Vlasenko,
  • M. A. Rassomakhin

摘要

Abstract

The anthropogenic calcium fluorosilicate “kutyukhinite” Ca5[SiO4]2F2 from burnt dumps of the Chelyabinsk coal basin has been studied by single crystal and powder X-ray diffraction analyses in a wide temperature range. “Kutyukhinite” (P21/a, a = 11.4985(4) Å, b = 5.0535(2) Å, c = 8.7848(3) Å, β = 109.008(4)°, V = 482.63(3) Å3, R1 = 0.0183) is an anthropogenic analogue of kumtyubeite, which belongs to the structural type of chondrodite. The empirical formula of “kutyukhinite” is Ca5.02[Si1.99O7.98]F2.04. Upon heating, its crystal structure expands anisotropically, with the direction of maximum thermal expansion close to the [100] direction. The relative change in bond lengths in silicon–oxygen tetrahedra with increasing temperature (27–927 °C) is less than 0.6%, which is within the margin of error. At the same time, the relative increase in the average bond length 〈Ca–O〉 varies from 1% (〈Ca1–O〉) to 1.5% (〈Ca3–O〉). The largest relative change of  2% was found for the average bond length 〈Ca3–F1〉.