The crystal structure of vyuntspakhite: A redetermination |
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Authors: | O V Yakubovich I M Steele |
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Institution: | 1.Faculty of Geology,Moscow State University,Moscow,Russia;2.University of Chicago,Chicago,USA |
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Abstract: | The crystal structure of the mineral vyuntspakhite (Y, TR)6{Al2(OH)3H1.48Si1.88O7]SiO4]SiO3(OH)]}2(a = 5.7551(11) Å, b = 14.752(3) Å, c = 15.906(4) Å, β = 96.046(4)°, sp. gr. P21/n, Z = 2), which had been established earlier in the pseudo-unit cell, is redetermined by X-ray diffraction (R = 0.040, T = 100 K). The redetermination of the structure shows that pronounced pseudotranslation along the axis c′ = c/3 is associated with the fact that Y(TR) atoms are related by a 1/3 translation along the 001] direction. Most of the hydrogen atoms are located. The crystal-chemical function of hydrogen bonds is analyzed. In the unit cell of vyuntspakhite, the cationic layers consisting of edge-sharing (Y,TR) eight-vertex polyhedra alternate along the b axis with mixed anionic layers composed of isolated Si tetrahedra (orthotetrahedra), Si2O7 double-tetrahedra (diortho) groups, Al five-vertex polyhedra, and Al2O8 double-tetrahedra groups linked by shared vertices and through hydrogen bonding. |
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