Actinyl Compounds with Hexavalent Elements (S, Cr, Se, Mo) – Structural Diversity, Nanoscale Chemistry, and Cellular Automata Modeling

Krivovichev, Sergey V.

doi:10.1002/ejic.201000168

Cited by 64 publications

(46 citation statements)

References 71 publications

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“…In the framework of this approach [36][37][38], the U and Se coordination polyhedra are symbolized by black and white nodes, respectively. The vertices are linked by an edge if two respective polyhedra share a common oxygen atom.…”

Section: Topological Analysismentioning

confidence: 99%

Topologically and geometrically flexible structural units in seven new organically templated uranyl selenates and selenite–selenates

Gurzhiy

Kovrugin

Tyumentseva

et al. 2015

Journal of Solid State Chemistry

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a b s t r a c tSingle crystals of seven novel uranyl oxysalts of selenium with protonated methylamine molecules, [C 2 Their crystal structures have been solved by direct methods and their uranyl selenate and selenite-selenate units investigated using black-and-white graphs from the viewpoints of topology of interpolyhedral linkages and isomeric variations. The crystal structure of IV is based upon complex layers with unique topology, which has not been observed previously in uranyl selenates. Investigations of the statistics and local distribution of the U-O br -Se bond angles demonstrates that shorter angles associate with undulations, whereas larger angles correspond to planar areas of the uranyl selenite layers.

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Section: Topological Analysismentioning

confidence: 99%

Topologically and geometrically flexible structural units in seven new organically templated uranyl selenates and selenite–selenates

Gurzhiy

Kovrugin

Tyumentseva

et al. 2015

Journal of Solid State Chemistry

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“…9 Actinide sulfates, chromates and selenates are known to form diverse and complex structures with such interesting structural features as cation-cation interactions, microporous frameworks and nanotubules. [10][11][12][13][14][15][16] Actinide molybdates and tungstates may adopt structure types more resembling dense complex oxides than oxosalts. 4 In comparison to molybdates, uranyl tungstates are less studied with relatively few reports available in the literature.…”

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confidence: 99%

Polytypism and oxo-tungstate polyhedra polymerization in novel complex uranyl tungstates

et al. 2012

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The chemistry of actinides is an important and currently active field of inorganic chemistry. Actinides and their compounds play a prime role in nuclear waste management and safety assessment. [1][2][3] In particular, investigations of complexation of uranyl ions 4-6 with oxygen-based complexes consisting of highvalent elements such as S, Cr, Se, Mo or W have high relevance for nuclear waste disposal, owing to their use in nuclear engineering (e.g., Mo 7 and W 8 are used in refractory alloys) or due to their formation in burn-up processes of nuclear fuel (Mo, Se). 9 Actinide sulfates, chromates and selenates are known to form diverse and complex structures with such interesting structural features as cation-cation interactions, microporous frameworks and nanotubules. [10][11][12][13][14][15][16] Actinide molybdates and tungstates may adopt structure types more resembling dense complex oxides than oxosalts. 4 In comparison to molybdates, uranyl tungstates are less studied with relatively few reports available in the literature. 17 The mixture was heated to 820°C for 4 h and cooled down to room temperature with the rate of 7°C h −1 . The obtained product consisted of yellowish crystals of 1 and 2 immersed within an amorphous yellow solid. Powder samples consisting of both 1 and 2 phases were prepared by heating a mixture of CsNO 3 (0.273 g, 1.40 mmol), UO 3 (0.400 g, 1.40 mmol) and WO 3 (0.324 g, 1.40 mmol) in a 1 : 1 : 1 molar ratio at 750°C for 72 h in a porcelain crucible. X-ray powder diffraction indicated that the sample is a mixture of α-and β-Cs 2 [(UO 2 ) 2 (W 2 O 9 )] in a ratio 1 : 4 (Fig. S1 †). Our attempts to obtain pure powders of either α-or β-Cs 2 [(UO 2 ) 2 (W 2 O 9 )] were not successful. Single crystals of 3 were obtained by high-temperature solid-state reaction of an initial mixture of RbNO 3 (0.103 g, 0.70 mmol), UO 3 (0.200 g, 0.70 mmol) and WO 3 (0.162 g, 0.70 mmol) with a Rb : U : W ratio equal to 1 : 1 : 1. The mixture was slowly heated to 870°C in a porcelain crucible and then cooled down to 400°C at a rate of 4°C h −1 . The product consisted of yellowish crystals of 3 in a glassy amorphous mass. Single crystals of the obtained phases were investigated by means of single-crystal X-ray diffraction analysis. It is noteworthy that the crystals of 1 were observed to be of considerably lower quality in comparison to the crystals of 2, which may indicate its lower stability.The structures of all three compounds are based upon 2D uranyl tungstate layers (Fig. 1). The layers in these structures are based on UO 2 2+ linear groups linked with oxo-tungstates polyhedra. In all three structures, U 6+ cations form linear uranyl groups, [OvUvO] 2+ , equatorially coordinated by five O atoms. In the structures of 1 and 2, UO 7 pentagonal bipyramids share edges to † Electronic supplementary information (ESI) available: Includes powder diffractograms and IR spectra. CCDC 881326-881328. For ESI and crystallographic data in CIF or other electronic format see

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“…The relations between the triplets are illustrated in Figure 6b, which represents an analogue of de Brujin diagram for cellular automata [25][26][27] that was considered as a model of crystallization processes [28,29]. The arrow lines in the diagram indicate the only possible sequence of triplets starting at the preceding triplet and ending at the following.…”

Section: I-iii Ii-iv I-v Ii-vii Iii-i Iv-ii V-viii Vi-i Vii-vi Viii-iimentioning

confidence: 99%

Kurchatovite and Clinokurchatovite, Ideally CaMgB2O5: An Example of Modular Polymorphism

et al. 2018

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Kurchatovite and clinokurchatovite, both of ideal composition CaMgB 2 O 5 , from the type localities (Solongo, Buryatia, Russia, and Sayak-IV, Kazakhstan, respectively) have been studied using electron microprobe and single-crystal X-ray diffraction methods. The empirical formulae of the samples are Ca for kurchatovite and clinokurchatovite, respectively. The crystal structures of the two minerals are similar and based upon two-dimensional blocks arranged parallel to the c axis in kurchatovite and parallel to the a axis in clinokurchatovite. The blocks are built up from diborate B 2 O 5 groups, and Ca 2+ and Mg 2+ cations in seven-and six-fold coordination, respectively. Detailed analysis of geometrical parameters of the adjacent blocks reveals that symmetrically different diborate groups have different degrees of conformation in terms of the δ angles between the planes of two BO 3 triangles sharing a common O atom, featuring two discrete sets of the δ values of ca. 55 • (B' blocks) and 34 • (B" blocks). The stacking of the blocks in clinokurchatovite can be presented as . . . (+B')(+B")(+B')(+B") . . . or [(+B')(+B")], whereas in kurchatovite it is more complex and corresponds to the sequence . . . (+B')(+B")(+B')(−B')(−B")(−B')(+B')(+B")(+B')(−B')(−B")(−B'). . . or [(+B')(+B")(+B')(−B')(−B")(−B')]. The B':B" ratios for clinokurchatovite and kurchatovite are 1:1 and 2:1, respectively. According to this description, the two minerals cannot be considered as polytypes and their mutual relationship corresponds to the term modular polymorphs. From the viewpoint of information-based measures of structural complexity, clinokurchatovite (I G = 4.170 bits/atom and I G,total = 300.235 bits/cell) is structurally simpler than kurchatovite (I G = 4.755 bits/atom and I G,total = 1027.056 bits/cell). The high structural complexity of kurchatovite can be inferred from the modular character of its structure. The analysis of structural combinatorics in terms of the modular approach allows to construct the whole family of theoretically possible "kurchatovite"-type structures that bear the same structural features common for kurchatovite and clinokurchatovite. However, the crystal structures of the latter minerals are the simplest and are the only ones that have been observed in nature. The absence of other possible structures is remarkable and can be explained by either the maximum-entropy of the least-action fundamental principles.

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Actinyl Compounds with Hexavalent Elements (S, Cr, Se, Mo) – Structural Diversity, Nanoscale Chemistry, and Cellular Automata Modeling

Cited by 64 publications

References 71 publications

Topologically and geometrically flexible structural units in seven new organically templated uranyl selenates and selenite–selenates

Topologically and geometrically flexible structural units in seven new organically templated uranyl selenates and selenite–selenates

Polytypism and oxo-tungstate polyhedra polymerization in novel complex uranyl tungstates

Kurchatovite and Clinokurchatovite, Ideally CaMgB2O5: An Example of Modular Polymorphism

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