Refinement of the crystal structure of kröhnkite

Hawthorne, Frank C.; Ferguson, R. B.

doi:10.1107/s0567740875006048

Cited by 82 publications

(68 citation statements)

References 8 publications

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“…Crystal structures of derriksite and another two synthetic compounds (Tables 1 and 2, Figure 1a-c), which are actually the same but were refined in different space groups, are based on the 1D units of the cc1-1:2-1 topological type (graph is an infinite chain of four-membered vertex-sharing rings). The graph corresponds to the type of chains, which were observed in the kröhnkite [63]. This topology is one of the most common and simplest chain topologies among U(VI)-bearing compounds with the [TO m ] n− groups (m = 3,4; T = S, Se, P, As).…”

Section: Topological Analysismentioning

confidence: 99%

Crystal Chemistry and Structural Complexity of Natural and Synthetic Uranyl Selenites

et al. 2019

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Comparison of the natural and synthetic phases allows an overview to be made and even an understanding of the crystal growth processes and mechanisms of the particular crystal structure formation. Thus, in this work, we review the crystal chemistry of the family of uranyl selenite compounds, paying special attention to the pathways of synthesis and topological analysis of the known crystal structures. Comparison of the isotypic natural and synthetic uranyl-bearing compounds suggests that uranyl selenite mineral formation requires heating, which most likely can be attributed to the radioactive decay. Structural complexity studies revealed that the majority of synthetic compounds have the topological symmetry of uranyl selenite building blocks equal to the structural symmetry, which means that the highest symmetry of uranyl complexes is preserved regardless of the interstitial filling of the structures. Whereas the real symmetry of U-Se complexes in the structures of minerals is lower than their topological symmetry, which means that interstitial cations and H 2 O molecules significantly affect the structural architecture of natural compounds. At the same time, structural complexity parameters for the whole structure are usually higher for the minerals than those for the synthetic compounds of a similar or close organization, which probably indicates the preferred existence of such natural-born architectures. In addition, the reexamination of the crystal structures of two uranyl selenite minerals guilleminite and demesmaekerite is reported. As a result of the single crystal X-ray diffraction analysis of demesmaekerite, Pb 2 Cu 5 [(UO 2 ) 2 (SeO 3 ) 6 (OH) 6 ](H 2 O) 2 , the H atoms positions belonging to the interstitial H 2 O molecules were assigned. The refinement of the guilleminite crystal structure allowed the determination of an additional site arranged within the void of the interlayer space and occupied by an H 2 O molecule, which suggests the formula of guilleminite to be written as Ba 3 . occurrence is limited to just a few localities. First, these are Musonoi and Shinkolobwe mines in DR Congo [6], two of the minerals were only found in the Repete mine (San Juan County, Utah, USA) [5], and a few more occurrences in Europe could be mentioned (small uranium deposit Zálesí in the Czech Republic, Liauzun in France, and La Creusaz U prospect in Switzerland) [8]. Nevertheless, apart from mineralogy, uranyl selenites are of great interest from the geochemical and radiochemical points of view. It is known that fission products contain 53 g per ton [9] of long-lived 79 Se isotope with a half-life of 1.1 × 10 6 years [10] after three years of nuclear fuel irradiation in the reactor. Thus, an understanding of the processes of mineral formation in nature and their synthetic analogs in laboratories can help in the processing of nuclear wastes. Crystal chemical and structural investigations are key points in such a material's scientific studies due to the essential knowledge of how the variation in the chemical composi...

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Section: Topological Analysismentioning

confidence: 99%

Crystal Chemistry and Structural Complexity of Natural and Synthetic Uranyl Selenites

et al. 2019

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“…For n = 2, two polymorphic phases have been identified (Petrova, Angelova & Macf~ek, 1996). One of them is built up of infinite kr6hnkite-type chains (Hawthorne & Ferguson, 1975), while in the other, the chains consist of CDS303 octahedra linked by alternating double ReO4 and tu bridges. The crystal structure of Cd(ReO4)2.4tu is built up of isolated trans-[M(ReO4)2tu4] clusters (Petrova, Angelova, Bakardjieva & Macf~ek, 1996).…”

Section: Commentmentioning

confidence: 99%

Molecular Adducts of Inorganic Salts. VII. Cadmium Tetraoxorhenium Hexakis(thiourea) Hydrate

Petrova¹,

Angelova²,

Macicek³

1997

Acta Crystallogr C

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“…2H20 phases. 1521 intensities were collected according to the experimental method of Hawthorne & Ferguson (1975); standard data-reduction procedures (including absorption corrections) resulted in 1216 (40-) observed reflexions. With scattering factors for neutral atoms (Cromer & Mann, 1968) and anomalous dispersion corrections from Cromer & Liberman (1970), the refinement converged to R=5.9 and Rw=6"3 %.…”

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confidence: 99%