scholarly journals Crystal Chemistry and Structural Complexity of Natural and Synthetic Uranyl Selenites

Crystals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 639 ◽  
Author(s):  
Vladislav V. Gurzhiy ◽  
Ivan V. Kuporev ◽  
Vadim M. Kovrugin ◽  
Mikhail N. Murashko ◽  
Anatoly V. Kasatkin ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Crystal Chemistry ◽  
Topological Analysis ◽  
Radioactive Decay ◽  
Structural Complexity ◽  
Building Blocks ◽  
Synthetic Compounds ◽  
Structural Architecture ◽  
Natural And Synthetic

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 H2O 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, Pb2Cu5[(UO2)2(SeO3)6(OH)6](H2O)2, the H atoms positions belonging to the interstitial H2O 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 H2O molecule, which suggests the formula of guilleminite to be written as Ba[(UO2)3(SeO3)2O2](H2O)4 instead of Ba[(UO2)3(SeO3)2O2](H2O)3.

Crystal structure relations in the binary system Li–Sn including the compound c-Li3Sb

2020 ◽  
Vol 235 (12) ◽  
pp. 581-590
Author(s):  
Patric Berger ◽  
Clemens Schmetterer ◽  
Herta Silvia Effenberger ◽  
Hans Flandorfer
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Topological Analysis ◽  
Building Blocks ◽  
Three Dimensions ◽  
Structural Elements ◽  
Compound C ◽  
Similarities And Differences ◽  
The Individual ◽  
Hierarchical Scheme

AbstractA topological analysis of the crystal structures of Li, Li–Sn compounds, Li8Sn3−xSbx and metastable c-Li3Sb showed that these structures can be described by a hierarchical scheme of building blocks based on atom blocks and polyhedra blocks, respectively. These blocks are linked in distinct ways to form the individual 3D atom arrangement. A common model was established for the construction of the mentioned structures from bespoke building blocks, for which bcc-Li is the aristotype. This latter structure can be described on the basis of hexa-capped cubes from which variants are derived through substitution of Li by Sn (or Sb). These are then combined into polyhedra blocks that are in turn assembled into polyhedra sequences. These latter are repeated and linked in three dimensions to form the whole crystal structure. At xSn ≥ 0.5, this mechanism changes and structural elements from bcc-Li and β-Sn can be observed in LiSn and Li2Sn5. In this work, we present the similarities and differences between the various crystal structures, the topological model with its construction rules and its limitations.

scholarly journals Crystal Chemistry and Structural Complexity of the Uranyl Carbonate Minerals and Synthetic Compounds

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 704
Author(s):  
Vladislav V. Gurzhiy ◽  
Sophia A. Kalashnikova ◽  
Ivan V. Kuporev ◽  
Jakub Plášil
Keyword(s):  
Crystal Chemistry ◽  
Room Temperature ◽  
Structural Complexity ◽  
Synthetic Compounds ◽  
International Mineralogical Association ◽  
Mineralogical Association ◽  
Uranyl Carbonate ◽  
Hydration State ◽  
Uranyl Phosphates ◽  
Structural Architecture

Uranyl carbonates are one of the largest groups of secondary uranium(VI)-bearing natural phases being represented by 40 minerals approved by the International Mineralogical Association, overtaken only by uranyl phosphates and uranyl sulfates. Uranyl carbonate phases form during the direct alteration of primary U ores on contact with groundwaters enriched by CO2, thus playing an important role in the release of U to the environment. The presence of uranyl carbonate phases has also been detected on the surface of “lavas” that were formed during the Chernobyl accident. It is of interest that with all the importance and prevalence of these phases, about a quarter of approved minerals still have undetermined crystal structures, and the number of synthetic phases for which the structures were determined is significantly inferior to structurally characterized natural uranyl carbonates. In this work, we review the crystal chemistry of natural and synthetic uranyl carbonate phases. The majority of synthetic analogs of minerals were obtained from aqueous solutions at room temperature, which directly points to the absence of specific environmental conditions (increased P or T) for the formation of natural uranyl carbonates. Uranyl carbonates do not have excellent topological diversity and are mainly composed of finite clusters with rigid structures. Thus the structural architecture of uranyl carbonates is largely governed by the interstitial cations and the hydration state of the compounds. The information content is usually higher for minerals than for synthetic compounds of similar or close chemical composition, which likely points to the higher stability and preferred architectures of natural compounds.

scholarly journals Crystal Chemical Relations in the Shchurovskyite Family: Synthesis and Crystal Structures of K2Cu[Cu3O]2(PO4)4 and K2.35Cu0.825[Cu3O]2(PO4)4

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 807
Author(s):  
Ilya V. Kornyakov ◽  
Sergey V. Krivovichev
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structural Complexity ◽  
Crystal Chemical ◽  
X Ray Diffraction ◽  
Complexity Measures ◽  
X Ray ◽  
The Family ◽  
Similarities And Differences ◽  
Related Compounds

Single crystals of two novel shchurovskyite-related compounds, K2Cu[Cu3O]2(PO4)4 (1) and K2.35Cu0.825[Cu3O]2(PO4)4 (2), were synthesized by crystallization from gaseous phase and structurally characterized using single-crystal X-ray diffraction analysis. The crystal structures of both compounds are based upon similar Cu-based layers, formed by rods of the [O2Cu6] dimers of oxocentered (OCu4) tetrahedra. The topologies of the layers show both similarities and differences from the shchurovskyite-type layers. The layers are connected in different fashions via additional Cu atoms located in the interlayer, in contrast to shchurovskyite, where the layers are linked by Ca2+ cations. The structures of the shchurovskyite family are characterized using information-based structural complexity measures, which demonstrate that the crystal structure of 1 is the simplest one, whereas that of 2 is the most complex in the family.

Crystal chemistry of zirconosilicates and their analogs: topological classification of MT frameworks and suprapolyhedral invariants

2002 ◽  
Vol 58 (2) ◽  
pp. 198-218 ◽  
Author(s):  
G. D. Ilyushin ◽  
V. A. Blatov
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Crystal Chemistry ◽  
Three Dimensional ◽  
Geometrical Interpretation ◽  
Topological Classification ◽  
Hierarchical Analysis ◽  
Framework Structure ◽  
Coordination Spheres

The first attempt is undertaken to consider systematically topological structures of zirconosilicates and their analogs (60 minerals and 34 synthetic phases), where the simplest structure units are MO6 octahedra and TO4 tetrahedra united by vertices ([TO4]:[MO6] = 1:1–6:1). A method of analysis and classification of mixed three-dimensional MT frameworks by topological types with coordination sequences {N k } is developed, which is based on the representation of crystal structure as a finite `reduced' graph. The method is optimized for the frameworks of any composition and complexity and implemented within the TOPOS3.2 program package. A procedure of hierarchical analysis of MT-framework structure organization is proposed, which is based on the concept of polyhedral microensemble (PME) being a geometrical interpretation of coordination sequences of M and T nodes. All 12 theoretically possible PMEs of MT 6 polyhedral composition are considered where T is a separate and/or connected tetrahedron. Using this methodology the MT frameworks in crystal structures of zirconosilicates and their analogs were analyzed within the first 12 coordination spheres of M and T nodes and related to 41 topological types. The structural correlations were revealed between rosenbuschite, lavenite, hiortdahlite, woehlerite, siedozerite and the minerals of the eudialyte family.

scholarly journals Refinement of the crystal structure of a synthetic non-stoichiometric Rb-feldspar

2001 ◽  
Vol 65 (4) ◽  
pp. 523-531 ◽  
Author(s):  
A. Kyono ◽  
M. Kimata
Keyword(s):  
Crystal Structure ◽  
Ir Spectra ◽  
Crystal Structures ◽  
Monoclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
Deviation From Stoichiometry ◽  
The Mean ◽  
Unit Formula ◽  
Natural And Synthetic

AbstractThe crystal structure of hydrothermally synthesized Rb-feldspar (monoclinic, space group C2/m, a= 8.839(2)Å, b= 13.035(2)Å, c= 7.175(2)Å, β = 116.11(1)8, V= 742.3(3)Å3, Z= 4) has been refined to a final R of 0.0574 for 692 independent X-ray reflections. Microprobe analyses of the Rb-feldspar suggest deviation from stoichiometry, with excess Si and Al, resulting in a unit formula of Rb0.811□0.127Al1.059Si3.003O8. Infrared (IR) spectra indicate the structural occupancy of large H2O content, which implies that the □Si4O8 substitution favours the structural incorporation of the H2O molecule at the M-site. The mean T–O distances are 1.632 Å for T1 and 1.645 Å for T2, revealing highly disordered (Al,Si) distribution with Al/Si = 0.245/0.755 (T1 site) and 0.255/0.745 (T2 site).There are two geochemical implications from this refinement: (1) identification of both rubicline triclinic with (Al,Si) ordered distribution and synthetic monoclinic RbAlSi3O8 with (Al,Si) disordered distribution implies that Rb cannot be one of factors disrupting the (Al,Si) ordered and disordered distributions in feldspars; and (2) natural and synthetic feldspars capable of accommodating the large cations tend to incorporate □Si4O8, excess Al and H2O components in their crystal structures.

Crystal chemistry of orthosilicates and their analogs: the classification by topological types of suprapolyhedral structural units

2002 ◽  
Vol 58 (6) ◽  
pp. 948-964 ◽  
Author(s):  
G. D. Ilyushin ◽  
V. A. Blatov ◽  
Yu. A. Zakutkin
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Crystal Structures ◽  
Crystal Chemistry ◽  
Topological Classification ◽  
Structural Units ◽  
Coordination Sequence ◽  
Coordination Spheres

A method is developed for the analysis and classification of orthosilicates and their analogs Mx (TO4) y containing M cations and tetrahedral TO4 anions. The method uses the concepts of coordination sequence and crystal structure `reduced' graphs and is optimized for orthostructures of any complexity. First, the suprapolyhedral level of crystal structure organization was studied, where T tetrahedra were considered as templates for condensing M polyhedra, constructing as a result T polyhedral microensembles. Using this methodology, the crystal structures of 54 orthosilicates and orthogermanates were analyzed within the first 12 coordination spheres of T nodes and were arranged into 21 topological types. The topological types were expanded with the analogs found within the orthostructures of phosphates, sulfates etc. T polyhedral microensembles were used for the topological classification of reconstruction mechanisms of thermal and baric phase transitions of orthosilicates.

Natural and synthetic compounds with kröhnkite-type chains: review and classification

2002 ◽  
Vol 217 (9) ◽  
Author(s):  
Michel Fleck ◽  
U. Kolitsch ◽  
B. Hertweck
Keyword(s):  
Crystal Structure ◽  
Synthetic Compounds ◽  
Natural And Synthetic

AbstractThe crystal structure of kröhnkite [Na

Crystal chemistry of tetraradial species. Part 4. Hydrogen bonding to aromatic π systems: crystal structures of fifteen tetraphenylborates with organic ammonium cations

1994 ◽  
Vol 72 (5) ◽  
pp. 1273-1293 ◽  
Author(s):  
Pradip K. Bakshi ◽  
Antony Linden ◽  
Beverly R. Vincent ◽  
Stephen P. Roe ◽  
D. Adhikesavalu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Crystal Chemistry ◽  
Phenyl Ring ◽  
Orientational Disorder ◽  
Compromise Solutions ◽  
The Mean ◽  
General Organization

The aim of this investigation is to provide a classification and examples of N—H …π (and also O—H …π) bonds to the aromatic π systems in organic ammonium tetraphenylborates that would serve as reference for X—H …π(arene) bonds in general. To this end the crystal structures of the tetraphenylborates of the following cations have been determined: Me3NH+, Et3NH+, quinuclidinium, DabcoH+, Et(iso-Pr)2NH+ (monohydrate), (Ph3B)NH[—(CH2)2—]2NHMe+ (Me2CO solvate), Me2NH2+ (MeCN and Et2CO solvates), Et2NH2+, (iso-Pr)2NH2+, azoniacycloheptane, guanidinium (monohydrate), MeNH3+, EtNH3+, and 1-adamantammonium (monohydrate). These structures contain a variety of normal, bifurcated, and trifurcated N—H …π bonds as well as normal O—H …π bonds to the phenyl groups of the anion. The X—H …π bonds will form whenever opportunity arises, even though the result may be unfavourable bonding geometry. Branched bonds and orientational disorder represent compromise solutions in situations where the H(X) hydrogens are presented with competing phenyl acceptors or where the general organization of the crystal structure offers unfavourable bonding conditions to these hydrogens. The distributions of the distances from X or H(X) to the centre of the phenyl-ring skeleton are analyzed in detail, as are also those of the mean X … C and H(X)… C distances to the ring carbons.

Crystal chemistry of tetraradial species. Part 2. Crystal structures of Et4NI, Ph4PBr•H2O, and Ph4PBr•2H2O

1988 ◽  
Vol 66 (12) ◽  
pp. 3060-3069 ◽  
Author(s):  
Beverly R. Vincent ◽  
Osvald Knop ◽  
Anthony Linden ◽  
T. Stanley Cameron ◽  
Katherine N. Robertson
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Crystal Chemistry ◽  
Cyclic Dimer ◽  
Nias Type ◽  
First Time

The crystal structure of Et4NI [Formula: see text], a = 8.860(2) Å, c = 6.933(1) Å, Z = 2) has been redetermined and those of Ph4PBr•H2O ([Formula: see text], a = 10.005(3) Å, b = 10.659(2) Å, c = 10.697(4) Å, α = 102.61(2)°, β = 83.39(3)°, γ = 108.09(3)°, Z = 2) and Ph4PBr•2H2O (Pnma, a = 16.255(4) Å, b = 10.810(4) Å, c = 12.667(9) Å, Z = 4) have been determined for the first time. In the Et4NI structure Et4N+ cations in an extended S4 conformation and I− anions are arranged in a zincblende-type packing. The two hydrate structures are ionic and very similar. The anion in the monohydrate is a centrosymmetric cyclic dimer [Br2(OH2)2]2−; in the dihydrate the anion, which is an almost planar infinite [Br−(OH2)4/2]x chain 11b, appears to be of a novel type. If the H2O molecules are not considered, the ion packing in both hydrates may be regarded as of the anti-NiAs type. The ion packing in R4EX structures and the conformation of the Et4N+ ion in crystals are discussed in some detail.

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