Crystal structure of the (Mg,Fe)[UO2(P,As)O4]2 · 10H2O solid solution—A novel mineral variety of saléeite

• Published in: Crystallography reports 2008-09, Vol.53 (5), p.764-770
• Main Authors: Yakubovich, O. V., Steele, I. M., Atencio, D., Menezes, L. A., Chukanov, N. V.
• Format: Article
• Language: English
• Subjects: Crystallography and Scattering Methods; Physics; Physics and Astronomy; Structure of Inorganic Compounds
• ISSN: 1063-7745; 1562-689X
• DOI: 10.1134/S1063774508050064

The crystal structure of a novel variety {[(Mg 0.81 Fe 0.19 )(H 2 O) 6 ](H 2 O) 4 }{(UO 2 )[(P 0.67 As 0.33 )O 4 ]} 2 of the mineral saléeite is determined using X-ray diffraction (Bruker Smart diffractometer, λMo K α , graphite monochromator, 2θ max = 56.62°, R = 0.0321 for 2317 reflections, T = 100 K). The main crystal data are as follows: a = 6.952(6) Å, b = 19.865(5) Å, c = 6.969(2) Å, β = 90.806(4)°, space group P 12 1 / n 1, Z = 2, and ρ calcd = 3.34 g/cm 3 . It is shown that the structure is formed by alternating (along the [010] direction) anionic layers, which are composed of uranium bipyramids and T (P,As) tetrahedra, and cation layers consisting of M (Mg,Fe) octahedra and water molecules, which are joined through a system of asymmetric hydrogen bonds. The hydrogen atoms are located, the scheme of hydrogen bonds is established, and their geometric characteristics are calculated.