Titre
Synchrotron diffraction study of the crystal structure of Ca(UO2)6(SO4)2O2(OH)6·12H2O, a natural phase related to Uranopilite
Type
article
Institution
UNIL/CHUV/Unisanté + institutions partenaires
Périodique
Auteur(s)
Krivovichev, Sergey
Auteure/Auteur
Meisser, Nicolas
Auteure/Auteur
Brugger, Joel
Auteure/Auteur
Chernyshov, Dmitry
Auteure/Auteur
Gurzhiy, Vladislav
Auteure/Auteur
Liens vers les personnes
Liens vers les unités
ISSN
2075-163X
Statut éditorial
Publié
Date de publication
2018
Volume
8
Première page
569
Dernière page/numéro d’article
570
Peer-reviewed
Oui
Langue
anglais
Résumé
The crystal structure of a novel natural uranyl sulfate, Ca(UO2)6(SO4)2O2(OH)6·12H2O (CaUS), has been determined using data collected under ambient conditions at the Swiss–Norwegian beamline BM01 of the European Synchrotron Research Facility (ESRF). The compound is monoclinic, P21/c, a = 11.931(2), b = 14.246(6), c = 20.873(4) Å, β = 102.768(15), V = 3460.1(18) Å3, and R1 = 0.172 for 3805 unique observed reflections. The crystal structure contains six symmetrically independent U6+ atoms forming (UO7) pentagonal bipyramids that share O…O edges to form hexamers oriented parallel to the (010) plane and extended along [1–20]. The hexamers are linked via (SO4) groups to form [(UO2)6(SO4)2O2(OH)6(H2O)4]2− chains running along the c-axis. The adjacent chains are arranged into sheets parallel to (010). The Ca2+ ions are coordinated by seven O atoms, and are located in between the sheets, providing their linkage into a three-dimensional structure. The crystal structure of CaUS is closely related to that of uranopilite, (UO2)6(SO4)O2(OH)6·14H2O, which is also based upon uranyl sulfate chains consisting of hexameric units formed by the polymerization of six (UO7) pentagonal bipyramids. However, in uranopilite, each (SO4) tetrahedron shares its four O atoms with (UO7) bipyramids, whereas in CaUS, each sulfate group is linked to three uranyl ions only, and has one O atom (O16) linked to the Ca2+ cation. The chains are also different in the U:S ratio, which is equal to 6:1 for uranopilite and 3:1 for CaUS. The information-based structural complexity parameters for CaUS were calculated taking into account H atoms show that the crystal structure of this phase should be described as very complex, possessing 6.304 bits/atom and 1991.995 bits/cell. The high structural complexity of CaUS can be explained by the high topological complexity of the uranyl sulfate chain based upon uranyl hydroxo/oxo hexamers and the high hydration character of the phase.
PID Serval
serval:BIB_76B13B6DAB45
URL éditeur
Open Access
Oui
Date de création
2021-03-18T10:56:47.376Z
Date de création dans IRIS
2025-05-21T04:11:41Z
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Nom
minerals-08-00569.pdf
Version du manuscrit
published
Licence
https://creativecommons.org/licenses/by-nc-nd/4.0
Taille
2.65 MB
Format
Adobe PDF
PID Serval
serval:BIB_76B13B6DAB45.P001
URN
urn:nbn:ch:serval-BIB_76B13B6DAB456
Somme de contrôle
(MD5):88d1c3cf136214421f77a65edc689361