Geology of Ore Deposits
Volume 50, Number 8, 789-794, DOI: 10.1134/S1075701508080163

Mineralogical Crystallography

Crystal chemistry of selenates with mineral-like structures: V. Crystal structures of (H3O)2[(UO2)(SeO4)2(H2O)](H2O)2 and (H3O)2[(UO2)(SeO4)2(H2O)](H2O), new compounds with rhomboclase and goldichite topology

S. V. Krivovichev

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Abstract

The crystal structures of two new compounds (H3O)2[(UO2)(SeO4)2(H2O)](H2O)2 (1, orthorhombic, Pnma, a = 14.0328(18), b = 11.6412(13), c = 8.2146(13) Å, V = 134.9(3) Å3) and (H3O)2[(UO2)(SeO4)2(H2O)](H2O) (2, monoclinic, P21/c, a = 7.8670(12), b = 7.5357(7), c = 21.386(3) Å, β = 101.484(12)°, V = 1242.5(3) Å3) have been solved by direct methods and refined to R 1 = 0.076 and 0.080, respectively. The structures of both compounds contain sheet complexes [(UO2)(SeO4)2]2− formed by cornershared [(UO2)O4(H2O)] bipyramids and SeO4 tetrahedrons. The sheets are parallel to the (100) plane in structure 1 and to (−102) in structure 2. The [(UO2)(SeO4)2(H2O)]2− layers are linked by hydrogen bonds via interlayer groups H2O and H3O+. The sheet topologies in structures 1 and 2 are different and correspond to the topologies of octahedral and tetrahedral complexes in rhomboclase (H2O2)+[Fe(SO4)2(H2O)2] and goldichite K[Fe(SO4)2(H2O)2](H2O)2, respectively.
Original Russian Text © S.V. Krivovichev, 2008, published in Zapiski Rossiiskogo Mineralogicheskogo Obshchestva, 2008, Pt CXXXVII, No. 1, pp. 54–61.

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