54 results on '"Krivovichev SV"'
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2. Reply to 'Experimental measurement of assembly indices are required to determine the threshold for life'.
- Author
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Hazen RM, Burns PC, Cleaves Ii HJ, Downs RT, Krivovichev SV, and Wong ML
- Subjects
- Models, Biological
- Abstract
We clarify misunderstandings of Walker et al. (Walker et al. 2024 J. R. Soc. Interface 21, 20240367 (doi:10.1098/rsif.2024.0367)) related to studies of the assembly pathways of molecular subunits in minerals. The finding that these subunits have calculated assembly pathways less than approximately 25 informs a central premise of Assembly Theory-that only life can produce numerous copies of molecules with assembly indices above a threshold value. What that threshold value might be, and whether the same value applies to chemical systems as different as organic and inorganic molecules, are questions deserving of additional study.
- Published
- 2024
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3. Molecular assembly indices of mineral heteropolyanions: some abiotic molecules are as complex as large biomolecules.
- Author
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Hazen RM, Burns PC, Cleaves HJ 2nd, Downs RT, Krivovichev SV, and Wong ML
- Subjects
- Molecular Conformation, Minerals chemistry, Water
- Abstract
Molecular assembly indices, which measure the number of unique sequential steps theoretically required to construct a three-dimensional molecule from its constituent atomic bonds, have been proposed as potential biosignatures. A central hypothesis of assembly theory is that any molecule with an assembly index ≥15 found in significant local concentrations represents an unambiguous sign of life. We show that abiotic molecule-like heteropolyanions, which assemble in aqueous solution as precursors to some mineral crystals, range in molecular assembly indices from 2 for H
2 CO3 or Si(OH)4 groups to as large as 21 for the most complex known molecule-like subunits in the rare minerals ewingite and ilmajokite. Therefore, values of molecular assembly indices ≥15 do not represent unambiguous biosignatures.- Published
- 2024
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4. The AM-4 Family of Layered Titanosilicates: Single-Crystal-to-Single-Crystal Transformation, Synthesis and Ionic Conductivity.
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Kalashnikova GO, Krivovichev SV, Yakovenchuk VN, Selivanova EA, Avdontceva MS, Ivanyuk GY, Pakhomovsky YA, Gryaznova DV, Kabanova NA, Morkhova YA, Sinel'shchikova OY, Bocharov VN, Nikolaev AI, Goychuk OF, Volkov SN, and Panikorovskii TL
- Abstract
Flexible crystal() structures, which exhibit() single-crystal()-to-single-crystal() (SCSC) transformations(), are attracting attention() in many applied aspects: magnetic() switches, catalysis, ferroelectrics and sorption. Acid treatment() for titanosilicate material() AM-4 and natural() compounds with the same structures led to SCSC transformation() by loss() Na
+ , Li+ and Zn2+ cations with large structural() changes (20% of the unit()-cell() volume()). The conservation() of crystallinity through complex() transformation() is possible due() to the formation() of a strong hydrogen bonding() system(). The mechanism() of transformation() has been characterized using single-crystal() X-ray() diffraction analysis(), powder() diffraction, Rietvield refinement, Raman spectroscopy and electron microscopy. The low migration() energy() of cations in the considered materials() is confirmed using bond()-valence and density() functional() theory() calculations, and the ion conductivity of the AM-4 family's materials() has been experimentally verified.- Published
- 2023
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5. One of Nature's Puzzles Is Assembled: Analog of the Earth's Most Complex Mineral, Ewingite, Synthesized in a Laboratory.
- Author
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Tyumentseva OS, Kornyakov IV, Kasatkin AV, Plášil J, Krzhizhanovskaya MG, Krivovichev SV, Burns PC, and Gurzhiy VV
- Abstract
Through the combination of low-temperature hydrothermal synthesis and room-temperature evaporation, a synthetic phase similar in composition and crystal structure to the Earth's most complex mineral, ewingite, was obtained. The crystal structures of both natural and synthetic compounds are based on supertetrahedral uranyl-carbonate nanoclusters that are arranged according to the cubic body-centered lattice principle. The structure and composition of the uranyl carbonate nanocluster were refined using the data on synthetic material. Although the stability of natural ewingite is higher (according to visual observation and experimental studies), the synthetic phase can be regarded as a primary and/or metastable reaction product which further re-crystallizes into a more stable form under environmental conditions.
- Published
- 2022
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6. The role of local heteropolyhedral substitutions in the stoichiometry, topological characteristics and ion-migration paths in the eudialyte-related structures: a quantitative analysis.
- Author
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Aksenov SM, Kabanova NA, Chukanov NV, Panikorovskii TL, Blatov VA, and Krivovichev SV
- Subjects
- Cations, Models, Molecular, Sodium
- Abstract
Topological analysis of the heteropolyhedral MT framework (where M and T are octahedral and tetrahedral cations, respectively) in the eudialyte-type structure and its derivatives was performed based on a natural tiling analysis of the 3D cation. To analyze the migration paths of sodium cations in these structures, the Voronoi method was used. The parental eudialyte-type MT framework is formed by isolated ZO
6 octahedra, six-membered [M(1)6 O24 ] rings of edge-sharing M(1)O6 octahedra, and two kinds of rings of tetrahedra, [Si3 O9 ] and [Si9 O27 ]. Different occupancies of M(2), M(3) and M(4) sites with variable coordination numbers by the additional Q, T* and M* cations, respectively, result in 12 different types of the MT framework. Based on the results of natural tilings calculations as well as theoretical analysis of migration paths, it is found that Na+ ions can migrate through six- and seven-membered rings, while all other rings are too small for the migration. In eight types of MT frameworks, Na+ -ion migration and diffusion is possible at ambient temperature and pressure, while in four other types cages are connected by narrow windows and, as a result, the Na+ diffusion in them is complicated at ambient conditions because of the window diameter, but may be possible either at higher temperatures or under mild geological conditions for long periods of time.- Published
- 2022
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7. Expanding the Averievite Family, ( MX )Cu 5 O 2 ( T 5+ O 4 ) 2 ( T 5+ = P, V; M = K, Rb, Cs, Cu; X = Cl, Br): Synthesis and Single-Crystal X-ray Diffraction Study.
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Kornyakov IV, Vladimirova VA, Siidra OI, and Krivovichev SV
- Abstract
Averievite-type compounds with the general formula ( MX )[Cu
5 O2 ( T O4 )], where M = alkali metal, X = halogen and T = P, V, have been synthesized by crystallization from gases and structurally characterized for six different compositions: 1 ( M = Cs; X = Cl; T = P), 2 ( M = Cs; X = Cl; T = V), 3 ( M = Rb; X = Cl; T = P), 4 ( M = K; X = Br; T = P), 5 ( M = K; X = Cl; T = P) and 6 ( M = Cu; X = Cl; T = V). The crystal structures of the compounds are based upon the same structural unit, the layer consisting of a kagome lattice of Cu2+ ions and are composed from corner-sharing (OCu4 ) anion-centered tetrahedra. Each tetrahedron shares common corners with three neighboring tetrahedra, forming hexagonal rings, linked into the two-dimensional [O2 Cu5 ]6+ sheets parallel to (001). The layers are interlinked by ( T5+ O4 ) tetrahedra ( T5+ = V, P) attached to the bases of the oxocentered tetrahedra in a "face-to-face" manner. The resulting electroneutral 3D framework {[O2 Cu5 ]( T5+ O4 )2 }0 possesses channels occupied by monovalent metal cations M+ and halide ions X- . The halide ions are located at the centers of the hexagonal rings of the kagome nets, whereas the metal cations are in the interlayer space. There are at least four different structure types of the averievite-type compounds: the P -3 m 1 archetype, the 2 × 2 × 1 superstructure with the P -3 space group, the monoclinically distorted 1 × 1 × 2 superstructure with the C 2/ c symmetry and the low-temperature P 21 / c superstructure with a doubled unit cell relative to the high-temperature archetype. The formation of a particular structure type is controlled by the interplay of the chemical composition and temperature. Changing the chemical composition may lead to modification of the structure type, which opens up the possibility to tune the geometrical parameters of the kagome net of Cu2+ ions.- Published
- 2021
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8. Embedding parallelohedra into primitive cubic networks and structural automata description.
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Bouniaev MM and Krivovichev SV
- Abstract
The main goal of the paper is to contribute to the agenda of developing an algorithmic model for crystallization and measuring the complexity of crystals by constructing embeddings of 3D parallelohedra into a primitive cubic network (pcu net). It is proved that any parallelohedron P as well as tiling by P, except the rhombic dodecahedron, can be embedded into the 3D pcu net. It is proved that for the rhombic dodecahedron embedding into the 3D pcu net does not exist; however, embedding into the 4D pcu net exists. The question of how many ways the embedding of a parallelohedron can be constructed is answered. For each parallelohedron, the deterministic finite automaton is developed which models the growth of the crystalline structure with the same combinatorial type as the given parallelohedron.
- Published
- 2020
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9. Producing highly complicated materials. Nature does it better.
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Bindi L, Nespolo M, Krivovichev SV, Chapuis G, and Biagioni C
- Abstract
Through the years, mineralogical studies have produced a tremendous amount of data on the atomic arrangement and mineral properties. Quite often, structural analysis has led to elucidate the role played by minor components, giving interesting insights into the physico-chemical conditions of mineral crystallization and allowing the description of unpredictable structures that represented a body of knowledge critical for assessing their technological potentialities. Using such a rich database, containing many basic acquisitions, further steps became appropriate and possible, into the directions of more advanced knowledge frontiers. Some of these frontiers assume the name of modularity, complexity, aperiodicity, and matter organization at not conventional levels, and will be discussed in this review.
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- 2020
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10. Polyoxometalate clusters in minerals: review and complexity analysis.
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Krivovichev SV
- Abstract
Most research on polyoxometalates (POMs) has been devoted to synthetic compounds. However, recent mineralogical discoveries of POMs in mineral structures demonstrate their importance in geochemical systems. In total, 15 different types of POM nanoscale-size clusters in minerals are described herein, which occur in 42 different mineral species. The topological diversity of POM clusters in minerals is rather restricted compared to the multitude of moieties reported for synthetic compounds, but the lists of synthetic and natural POMs do not overlap completely. The metal-oxo clusters in the crystal structures of the vanarsite-group minerals ([As
3+ V4+ 2 V5+ 10 As5+ 6 O51 ]7- ), bouazzerite and whitecapsite ([M3+ 3 Fe7 (AsO4 )9 O8-;n (OH)n ]), putnisite ([Cr3+ 8 (OH)16 (CO3 )8 ]8- ), and ewingite ([(UO2 )24 (CO3 )30 O4 (OH)12 (H2 O)8 ]32- ) contain metal-oxo clusters that have no close chemical or topological analogues in synthetic chemistry. The interesting feature of the POM cluster topologies in minerals is the presence of unusual coordination of metal atoms enforced by the topological restraints imposed upon the cluster geometry (the cubic coordination of Fe3+ and Ti4+ ions in arsmirandite and lehmannite, respectively, and the trigonal prismatic coordination of Fe3+ in bouazzerite and whitecapsite). Complexity analysis indicates that ewingite and morrisonite are the first and the second most structurally complex minerals known so far. The formation of nanoscale clusters can be viewed as one of the leading mechanisms of generating structural complexity in both minerals and synthetic inorganic crystalline compounds. The discovery of POM minerals is one of the specific landmarks of descriptive mineralogy and mineralogical crystallography of our time.- Published
- 2020
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11. The Fedorov-Groth law revisited: complexity analysis using mineralogical data.
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Krivovichev SV and Krivovichev VG
- Abstract
The Fedorov-Groth law points out that, on average, chemical simplicity corresponds to higher symmetry, and chemically complex compounds usually have lower symmetry than chemically simple compounds. Using mineralogical data, it is demonstrated that the Fedorov-Groth law is valid and statistically meaningful, when chemical complexity is expressed as the amount of Shannon chemical information per atom and the degree of symmetry as the order of the point group of a mineral.
- Published
- 2020
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12. Polyoxometalate chemistry at volcanoes: discovery of a novel class of polyoxocuprate nanoclusters in fumarolic minerals.
- Author
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Britvin SN, Pekov IV, Yapaskurt VO, Koshlyakova NN, Göttlicher J, Krivovichev SV, Turchkova AG, and Sidorov EG
- Abstract
Polyoxometalate (POM) chemistry is an important avenue of comprehensive chemical research, due to the broad chemical, topological and structural variations of multinuclear polyoxoanions that result in advanced functionality of their derivatives. The majority of compounds in the polyoxometalate kingdom are synthesized under laboratory conditions. However, Nature has its own labs with the conditions often unconceivable to the mankind. The striking example of such a unique environment is volcanic fumaroles - the natural factories of gas-transport synthesis. We herein report on the discovery of a novel class of complex polyoxocuprates grown in the hot active fumaroles of the Tolbachik volcano at the Kamchatka Peninsula, Russia. The cuboctahedral nanoclusters {[MCu
12 O8 ](AsO4 )8 } are stabilized by the core Fe(III) or Ti(IV) cations residing in the unique cubic coordination. The nanoclusters are uniformly dispersed over the anion- and cation-deficient NaCl matrix. Our discovery might have promising implications for synthetic chemistry, indicating the possibility of preparation of complex polyoxocuprates by chemical vapor transport (CVT) techniques that emulate formation of minerals in high-temperature volcanic fumaroles.- Published
- 2020
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13. Extraordinary structural complexity of ilmajokite: a multilevel hierarchical framework structure of natural origin.
- Author
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Zolotarev AA Jr, Krivovichev SV, Cámara F, Bindi L, Zhitova ES, Hawthorne F, and Sokolova E
- Abstract
The crystal structure of ilmajokite, a rare Na-K-Ba-Ce-titanosilicate from the Khibiny mountains, Kola peninsula, Russia, has been solved using single-crystal X-ray diffraction data. The crystal structure is based on a 3D titanosilicate framework consisting of trigonal prismatic titanosilicate (TPTS) clusters centered by Ce
3+ in [9]-coordination. Four adjacent TPTS clusters are linked into four-membered rings within the (010) plane and connected via ribbons parallel to 101. The ribbons are organized into layers parallel to (010) and modulated along the a axis with a modulation wavelength of c sinβ = 32.91 Å and an amplitude of ∼ b /2 = 13.89 Å. The layers are linked by additional silicate tetrahedra. Na+ , K+ , Ba2+ and H2 O groups occur in the framework cavities and have different occupancies and coordination environments. The crystal structure of ilmajokite can be separated into eight hierarchical levels: atoms, coordination polyhedra, TPTS clusters, rings, ribbons, layers, the framework and the whole structure. The information-based analysis allows estimation of the complexity of the structure as 8.468 bits per atom and 11990.129 bits per cell. According to this analysis, ilmajokite is the third-most complex mineral known to date after ewingite and morrisonite, and is the most complex mineral framework structure, comparable in complexity to paulingite-(Ca) (11 590.532 bits per cell)., (© Zolotarev et al. 2020.)- Published
- 2020
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14. Chemically Induced Polytypic Phase Transitions in the Mg[(UO 2 )( T O 4 ) 2 (H 2 O)](H 2 O) 4 ( T = S, Se) System.
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Gurzhiy VV, Tyumentseva OS, Izatulina AR, Krivovichev SV, and Tananaev IG
- Abstract
Chemically induced polytypic phase transitions have been observed during experimental investigations of crystallization in the mixed uranyl sulfate-selenate Mg[(UO
2 )( T O4 )2 (H2 O)](H2 O)4 ( T = S, Se) system. Three different structure types form in the system, depending upon the Se:S ratio in the initial aqueous solution. The phases with the Se/(Se + S) ratios (in mol %) in the ranges 0-9, 16-47, and 58-100 crystallize in the space groups P 21 , Pmn 21 , and P 21 / c , respectively. The structures of the phases are based upon the same type of uranyl-based sulfate/selenate chains that, through hydrogen bonds, are linked into pseudolayers of the same topological type. The layers are linked into three-dimensional structures via interlayer Mg-centered octahedra. The three structure types contain the same layers but with different stacking sequences that can be conveniently described as belonging to the 1 M , 2 O , and 2 M polytypic modifications. The Se-for-S substitution demonstrates a strong selectivity with preferential incorporation of Se into less tightly bonded T 1 site. The larger ionic radius of Se6+ relative to S6+ induces rotation of ( T 1O4 ) tetrahedra in the adjacent layers and reconstruction of the structure types. From the information-theoretic viewpoint, the intermediate Pmn 21 structure type is more complex than the monoclinic end-member structure types.- Published
- 2019
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15. Rb 2 CaCu 6 (PO 4 ) 4 O 2 , a novel oxophosphate with a shchurovskyite-type topology: synthesis, structure, magnetic properties and crystal chemistry of rubidium copper phosphates.
- Author
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Aksenov SM, Borovikova EY, Mironov VS, Yamnova NA, Volkov AS, Ksenofontov DA, Gurbanova OA, Dimitrova OV, Deyneko DV, Zvereva EA, Maximova OV, Krivovichev SV, Burns PC, and Vasiliev AN
- Abstract
Single crystals of Rb
2 CaCu6 (PO4 )4 O2 were synthesized by a hydrothermal method in the multicomponent system CuCl2 -Ca(OH)2 -RbCl-B2 O3 -Rb3 PO4 . The synthesis was carried out in the temperature range from 690 to 700 K and at the general pressure of 480-500 atm [1 atm = 101.325 kPa] from the mixture in the molar ratio 2CuO:CaO:Rb2 O:B2 O3 :P2 O5 . The crystals studied by single-crystal X-ray analysis were found to be monoclinic, space group C2, a = 16.8913 (4), b = 5.6406 (1), c = 8.3591 (3) Å, β = 93.919 (3)°, V = 794.57 (4) Å3 . The crystal structure of Rb2 CaCu6 (PO4 )4 O2 is similar to that of shchurovskyite and dmisokolovite and is based upon a heteropolyhedral open framework formed by polar layers of copper polyhedra linked via isolated PO4 tetrahedra. The presence of well-isolated 2D heteropolyhedral layers in the title compound suggests low-dimensional magnetic behavior which is masked, however, by the fierce competition between multiple ferromagnetic and antiferromagnetic exchange interactions. At TC = 25 K, Rb2 CaCu6 (PO4 )4 O2 reaches a magnetically ordered state with large residual magnetization.- Published
- 2019
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16. High pressure phase transitions of paracelsian BaAl 2 Si 2 O 8 .
- Author
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Gorelova LA, Pakhomova AS, Krivovichev SV, Dubrovinsky LS, and Kasatkin AV
- Abstract
Three new polymorphs of aluminosilicate paracelsian, BaAl
2 Si2 O8 , have been discovered using synchrotron-based in situ high-pressure single crystal X-ray diffraction. The first isosymmetric phase transition (from paracelsian-I to paracelsian-II) occurs between 3 and 6 GPa. The phase transition is associated with the formation of pentacoordinated Al3+ and Si4+ ions, which occurs in a stepwise fashion by sequential formation of Al-O and Si-O bonds additional to those in AlO4 and SiO4 tetrahedra, respectively. The next phase transition occurs between 25 and 28 GPa and is accompanied by the symmetry change from monoclinic (P21 /c) to orthorhombic (Pna21 ). The structure of paracelsian-III consists of SiO6 octahedra, AlO6 octahedra and distorted AlO4 tetrahedra, i.e. the transition is reconstructive and associated with the changes of Si4+ and Al3+ coordination, which show rather complex behaviour with the general tendency towards increasing coordination numbers. The third phase transition is observed between 28 and 32 GPa and results in the symmetry decreasing from Pna21 to Pn. The transition has a displacive character. In the course of the phase transformation pathway up to 32 GPa, the structure of polymorphs becomes denser: paracelsian-II is based upon elements of cubic and hexagonal close-packing arrangements of large O2- and Ba2+ ions, whereas, in the crystal structure of paracelsian-III and IV, this arrangement corresponds to 9-layer closest-packing with the layer sequence ABACACBCB.- Published
- 2019
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17. High-temperature Fe oxidation coupled with redistribution of framework cations in lobanovite, K 2 Na(Fe 2+ 4 Mg 2 Na)Ti 2 (Si 4 O 12 ) 2 O 2 (OH) 4 - the first titanosilicate case.
- Author
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Zhitova ES, Zolotarev AA, Hawthorne FC, Krivovichev SV, Yakovenchuk VN, and Goncharov AG
- Abstract
The high-temperature (HT) behaviour of lobanovite, K
2 Na(Fe2+ 4 Mg2 Na)Ti2 (Si4 O12 )2 O2 (OH)4 , was studied using in situ powder X-ray diffraction in the temperature range 25-1000°C and ex situ single-crystal X-ray diffraction of 17 crystals quenched from different temperatures. HT iron oxidation associated with dehydroxylation starts at 450°C, similar to other ferrous-hydroxy-rich heterophyllosilicates such as astrophyllite and bafertisite. A prominent feature of lobanovite HT crystal chemistry is the redistribution of Fe and Mg+Mn cations over the M(2), M(3), M(4) sites of the octahedral (O) layer that accompanies iron oxidation and dehydroxylation. This HT redistribution of cations has not been observed in titanosilicates until now, and seems to be triggered by the need to maintain bond strengths at the apical oxygen atom of the TiO5 pyramid in the heteropolyhedral (H) layer during oxidation-dehydroxylation. Comparison of the HT behaviour of lobanovite with five-coordinated Ti and astrophyllite with six-coordinated Ti shows that the geometry of the Ti polyhedron plays a key role in the HT behaviour of heterophyllosilicates. The thermal expansion, geometrical changes and redistribution of site occupancies which occur in lobanovite under increasing temperature are reported. A brief discussion is given of minerals in which the cation ordering (usually for Fe and Mg) occurs together with iron oxidation-dehydroxylation at elevated temperatures: micas, amphiboles and tourmalines. Now this list is expanded by the inclusion of titanosilicate minerals.- Published
- 2019
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18. Functionality in metal-organic framework minerals: proton conductivity, stability and potential for polymorphism.
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Huskić I, Novendra N, Lim DW, Topić F, Titi HM, Pekov IV, Krivovichev SV, Navrotsky A, Kitagawa H, and Friščić T
- Abstract
Rare metal-organic framework (MOF) minerals stepanovite and zhemchuzhnikovite can exhibit properties comparable to known oxalate MOF proton conductors, including high proton conductivity over a range of relative humidities at 25 °C, and retention of the framework structure upon thermal dehydration. They also have high thermodynamic stability, with a pronounced stabilizing effect of substituting aluminium for iron, illustrating a simple design to access stable, highly proton-conductive MOFs without using complex organic ligands.
- Published
- 2019
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19. On the origin of crystallinity: a lower bound for the regularity radius of Delone sets.
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Baburin IA, Bouniaev M, Dolbilin N, Erokhovets NY, Garber A, Krivovichev SV, and Schulte E
- Abstract
The mathematical conditions for the origin of long-range order or crystallinity in ideal crystals are one of the very fundamental problems of modern crystallography. It is widely believed that the (global) regularity of crystals is a consequence of `local order', in particular the repetition of local fragments, but the exact mathematical theory of this phenomenon is poorly known. In particular, most mathematical models for quasicrystals, for example Penrose tiling, have repetitive local fragments, but are not (globally) regular. The universal abstract models of any atomic arrangements are Delone sets, which are uniformly distributed discrete point sets in Euclidean d space. An ideal crystal is a regular or multi-regular system, that is, a Delone set, which is the orbit of a single point or finitely many points under a crystallographic group of isometries. The local theory of regular or multi-regular systems aims at finding sufficient local conditions for a Delone set X to be a regular or multi-regular system. One of the main goals is to estimate the regularity radius \hat{\rho}_d for Delone sets X in terms of the radius R of the largest `empty ball' for X. The celebrated `local criterion for regular systems' provides an upper bound for \hat{\rho_d} for any d. Better upper bounds are known for d ≤ 3. The present article establishes the lower bound \hat{\rho_d}\geq 2dR for all d, which is linear in d. The best previously known lower bound had been \hat{\rho}_d\geq 4R for d ≥ 2. The proof of the new lower bound is accomplished through explicit constructions of Delone sets with mutually equivalent (2dR - ℇ)-clusters, which are not regular systems. The two- and three-dimensional constructions are illustrated by examples. In addition to its fundamental importance, the obtained result is also relevant for the understanding of geometrical conditions of the formation of ordered and disordered arrangements in polytypic materials.
- Published
- 2018
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20. ℇ-RbCuCl 3 , a new polymorph of rubidium copper trichloride: synthesis, structure and structural complexity.
- Author
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Kornyakov IV, Krivovichev SV, Gurzhiy VV, and Leoni M
- Abstract
A novel polymorph of RbCuCl
3 (rubidium copper trichloride), denoted ℇ-RbCuCl3 , has been prepared by chemical vapour transport (CVT) from a mixture of CuO, CuCl2 , SeO2 and RbCl. The new polymorph crystallizes in the orthorhombic space group C2221 . The crystal structure is based on an octahedral framework of the 4H perovskite type. The Rb+ and Cl- ions form a four-layer closest-packing array with an ABCB sequence. The Cu2+ cations reside in octahedral cavities with a typical [4 + 2]-Jahn-Teller-distorted coordination, forming four short and two long Cu-Cl bonds. ℇ-RbCuCl3 is the most structurally complex and most dense among all currently known RbCuCl3 polymorphs, which allows us to suggest that it is a high-pressure phase, which is unstable under ambient conditions.- Published
- 2018
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21. The first lead cobalt phosphite, PbCo 2 (HPO 3 ) 3 .
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Kovrugin VM, Colmont M, Siidra OI, Krivovichev SV, Colis S, and Mentré O
- Abstract
Single crystals of a new lead cobalt phosphite, PbCo
2 (HPO3 )3 , have been synthesized using mild hydrothermal techniques and characterized by X-ray diffraction analysis, SQUID magnetic measurements, IR spectroscopy, UV/vis spectroscopy, thermogravimetric analysis, and scanning electron microscopy. PbCo2 (HPO3 )3 crystallizes in the non-centrosymmetric (NCS) R3m space group, a = 5.3145(15) Å, c = 25.494(7) Å, V = 623.6(4) Å3 . The crystal structure of PbCo2 (HPO3 )3 is based upon 2D heteropolyhedral blocks built up from Co2 O9 octahedral dimers and HPO3 pseudo-tetrahedra. Lead cations reside in the interlayer space of the structure. Here, the NCS character results reasonably from the cooperative Pb2+ lone electron pair arrangements, by analogy to the centrosymmetric compound (NH4 )2 Co2 (HPO3 )3 with similar but disordered blocks. A local twisting of specific HPO3 groups arises due to unreasonably short HH contacts between two phosphite oxoanions. In terms of the magnetic behavior, the new PbCo2 (HPO3 )3 phase demonstrates weak antiferromagnetic interactions inside the Co2 O9 dimers between cobalt ions as expected from the phosphite μ-O bridges.- Published
- 2017
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22. Xenon in Rigid Oxide Frameworks: Structure, Bonding and Explosive Properties of Layered Perovskite K 4 Xe 3 O 12 .
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Britvin SN, Kashtanov SA, Krivovichev SV, and Chukanov NV
- Abstract
The tendency of high-valence xenon to form consolidated oxide structures is herein supported by the study of K
4 Xe3 O12 , the first example of a layered xenon perovskite. Xenon seems to be the only nontransition element that can adopt single-cation oxide perovskite frameworks. At the same time, peculiarities of electronic structure of xenon impose specific features on the bonding within a perovskite structure. Weak supramolecular interactions known as aerogen bonds are the linkers that maintain structural integrity of perovskite slabs in K4 Xe3 O12 . The occurrence of aerogen bonding can provide an insight into the explosive properties of K4 Xe3 O12 : the weakness of supramolecular interactions allows consideration of them as possible trigger bonds responsible for the detonation sensitivity of layered xenon perovskite.- Published
- 2016
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23. Minerals with metal-organic framework structures.
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Huskić I, Pekov IV, Krivovichev SV, and Friščić T
- Subjects
- Chemistry Techniques, Analytical, Models, Molecular, Oxalates chemistry, Metals chemistry, Minerals chemistry, Organometallic Compounds chemistry
- Abstract
Metal-organic frameworks (MOFs) are an increasingly important family of advanced materials based on open, nanometer-scale metal-organic architectures, whose design and synthesis are based on the directed assembly of carefully designed subunits. We now demonstrate an unexpected link between mineralogy and MOF chemistry by discovering that the rare organic minerals stepanovite and zhemchuzhnikovite exhibit structures found in well-established magnetic and proton-conducting metal oxalate MOFs. Structures of stepanovite and zhemchuzhnikovite, exhibiting almost nanometer-wide and guest-filled apertures and channels, respectively, change the perspective of MOFs as exclusively artificial materials and represent, so far, unique examples of open framework architectures in organic minerals.
- Published
- 2016
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24. Structural complexity and configurational entropy of crystals.
- Author
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Krivovichev SV
- Abstract
Using a statistical approach, it is demonstrated that the complexity of a crystal structure measured as the Shannon information per atom [Krivovichev (2012). Acta Cryst. A68, 393-398] represents a negative contribution to the configurational entropy of a crystalline solid. This conclusion is in full accordance with the general agreement that information and entropy are reciprocal variables. It also agrees well with the understanding that complex structures possess lower entropies relative to their simpler counterparts. The obtained equation is consistent with the Landauer principle and points out that the information encoded in a crystal structure has a physical nature.
- Published
- 2016
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25. Structural Evolution from 0D Units to 3D Frameworks in Pb Oxyhalides: Unexpected Strongly Corrugated Layers in Pb7O6Br2.
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Siidra OI, Gogolin M, Lukina EA, Kabbour H, Bubnova RS, Mentré O, Agakhanov AA, Krivovichev SV, Colmont M, and Gesing T
- Abstract
Novel Pb7O6Br2 (1) lead oxybromide was prepared from Pb oxybromide melt by the "rapid quenching" route. Bonding scheme, thermal expansion, and structural properties were studied. The structural features of this unexpectedly complex phase are described on the basis of lone electron pair stereochemical activity and Pb-Br versus Pb-O bonding scheme. The structure of 1 contains a number of cavities, which can be assigned to the self-containments of the lone electron pairs on Pb(2+) cations. "Empty" □Pb4 chains are observed in between of the folding sides of the adjacent strongly corrugated oxocentered [Pb7O6](2+) layers. Highly isotropic thermal expansion of 1 appeared to be unexpected. The possible explanations of such a behavior in 1 are given. The structure of 1 is an interesting example of tetrahedral framework with mixed chemical bonding and is the densest known among Pb oxyhalides with the density of 18.4 tetrahedra/1000 Å(3). Current study shows that oxocentered layers derivatives from α-PbO can be very flexible and form rather dense three-dimensional structural topologies. The properties and structure are compared to other phases crystallizing in the anhydrous PbO-PbX2 (X = F, Cl, Br, I) systems, illustrate the complexity of lead oxyhalides, and reveal new and general pathways for the targeted synthesis of new phases with the Pb-O units of desired dimensionality. The indirect gap value of ∼ 2.04 eV obtained from generalized gradient approximation calculations demonstrates potentially good photocatalytic properties of 1.
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- 2015
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26. Perovskites with the Framework-Forming Xenon.
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Britvin SN, Kashtanov SA, Krzhizhanovskaya MG, Gurinov AA, Glumov OV, Strekopytov S, Kretser YL, Zaitsev AN, Chukanov NV, and Krivovichev SV
- Abstract
The Group 18 elements (noble gases) were the last ones in the periodic system to have not been encountered in perovskite structures. We herein report the synthesis of a new group of double perovskites KM(XeNaO6) (M = Ca, Sr, Ba) containing framework-forming xenon. The structures of the new compounds, like other double perovskites, are built up of the alternating sequence of corner-sharing (XeO6) and (NaO6) octahedra arranged in a three-dimensional rocksalt order. The fact that xenon can be incorporated into the perovskite structure provides new insights into the problem of Xe depletion in the atmosphere. Since octahedrally coordinated Xe(VIII) and Si(IV) exhibit close values of ionic radii (0.48 and 0.40 Å, respectively), one could assume that Xe(VIII) can be incorporated into hyperbaric frameworks such as MgSiO3 perovskite. The ability of Xe to form stable inorganic frameworks can further extend the rich and still enigmatic chemistry of this noble gas., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2015
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27. Oxocentered Cu(II) lead selenite honeycomb lattices hosting Cu(I)Cl2 groups obtained by chemical vapor transport reactions.
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Kovrugin VM, Colmont M, Siidra OI, Mentré O, Al-Shuray A, Gurzhiy VV, and Krivovichev SV
- Abstract
Chemical vapor transport (CVT) reactions were used to prepare three modular mixed-valent Cu(I)-Cu(II) compounds, (Pb2Cu(2+)9O4)(SeO3)4(Cu(+)Cl(2))Cl5 (1), (PbCu(2+)5O2)(SeO3)2(Cu(+)Cl2)Cl3 (2), and (Pb(x)Cu(2+)(6-x)O2)(SeO3)2(Cu(+)Cl2)K(1-x)Cl(4-x) (x = 0.20) (3). In their crystal structures chains of anion-centered (OCu(2+)4) and (OCu(2+)3Pb) tetrahedra form honeycomb-like double layers with cavities occupied by linear [Cu(+)Cl2](-) groups.
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- 2015
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28. pH controlled pathway and systematic hydrothermal phase diagram for elaboration of synthetic lead nickel selenites.
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Kovrugin VM, Colmont M, Terryn C, Colis S, Siidra OI, Krivovichev SV, and Mentré O
- Subjects
- Hydrogen-Ion Concentration, Hot Temperature, Lead chemistry, Nickel chemistry, Selenious Acid chemistry
- Abstract
The PbO-NiO-SeO2 ternary system was fully studied using constant hydrothermal conditions at 473 K. It yields the establishment of the corresponding phase diagram using a systematic assignment of reaction products by both powder and single-crystal X-ray diffraction. It leads to the preparation of three novel lead nickel selenites, α-PbNi(SeO3)2 (I), β-PbNi(SeO3)2 (II), and PbNi2(SeO2OH)2(SeO3)2 (III), and one novel lead cobalt selenite, α-PbCo(SeO3)2 (IV), which have been structurally characterized. The crystal structures of the α-forms I, IV, and III are based on a 3D complex nickel selenite frameworks, whereas the β-PbNi(SeO3)2 modification (II) consists of nickel selenite sheets stacked in a noncentrosymmetric structure, second-harmonic generation active. The pH value of the starting solution was shown to play an essential role in the reactive processes. Magnetic measurements of I, III, and IV are discussed.
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- 2015
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29. Earth's Phosphides in Levant and insights into the source of Archean prebiotic phosphorus.
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Britvin SN, Murashko MN, Vapnik Y, Polekhovsky YS, and Krivovichev SV
- Abstract
Natural phosphides--the minerals containing phosphorus in a redox state lower than zero--are common constituents of meteorites but virtually unknown on the Earth. Herein we present the first rich occurrence of iron-nickel phosphides of terrestrial origin. Phosphide-bearing rocks are exposed in three localities in the surroundings of the Dead Sea, Levant: in the northern Negev Desert, Israel and Transjordan Plateau, south of Amman, Jordan. Seven minerals from the ternary Fe-Ni-P system have been identified with five of them, NiP2, Ni5P4, Ni2P, FeP and FeP2, previously unknown in nature. The results of the present study could provide a new insight on the terrestrial origin of natural phosphides--the most likely source of reactive prebiotic phosphorus at the times of the early Earth.
- Published
- 2015
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30. Which inorganic structures are the most complex?
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Krivovichev SV
- Abstract
The discovery of the diffraction of X-rays on crystals opened up a new era in our understanding of nature, leading to a multitude of striking discoveries about the structures and functions of matter on the atomic and molecular scales. Over the last hundred years, about 150,000 of inorganic crystal structures have been elucidated and visualized. The advent of new technologies, such as area detectors and synchrotron radiation, led to the solution of structures of unprecedented complexity. However, the very notion of structural complexity of crystals still lacks an unambiguous quantitative definition. In this Minireview we use information theory to characterize complexity of inorganic structures in terms of their information content., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
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- 2014
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31. Synthesis and modular structural architectures of mineralogically inspired novel complex Pb oxyhalides.
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Siidra OI, Zinyakhina DO, Zadoya AI, Krivovichev SV, and Turner RW
- Abstract
Three novel Pb oxyhalides, Pb3[O10Pb20](GeO4)4Cl10 (1), [O16Pb22][OPb](OH)I10(I,Br)(H2O) (2), and Pb5.5Si0.5O6Cl (3), have been prepared by high-temperature solid-state reactions (1 and 3) and hydrothermal method (2). The structure of 1 is based upon novel [O10Pb20](20+) layers of edge- and corner-sharing oxocentered OPb4 tetrahedra with cavities occupied by the GeO4 tetrahedral anions. The interlayer space contains low-occupied Pb sites and Cl(-) anions. The structure of 2 contains unique [O16Pb22][12+] layers of edge-sharing OPb4 tetrahedra with X(-) ions (X = I, Br) in and in between the layers. The structure of 3 is the first example of the Pb oxyhalide with the 3:1 ratio between the O-Pb and X sheets (X = halide). The unprecedented structure topologies and architectures observed in the title compounds are closely related to those observed in rare natural Pb oxyhalides that have no synthetic analogues to date.
- Published
- 2013
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32. Anion-centered tetrahedra in inorganic compounds.
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Krivovichev SV, Mentré O, Siidra OI, Colmont M, and Filatov SK
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- 2013
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33. Crystal structures and variable magnetism of PbCu2(XO3)2Cl2 with X = Se, Te.
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Berdonosov PS, Janson O, Olenev AV, Krivovichev SV, Rosner H, Dolgikh VA, and Tsirlin AA
- Abstract
Novel Cu(2+)-based compounds PbCu2(SeO3)2Cl2 (space group C2/c; a = 13.056(1) Å; b = 9.5567(9) Å; c = 6.9006(6) Å; β = 90.529(7)°; RI = 0.0371) and PbCu2(TeO3)2Cl2 (space group P2(1); a = 7.2401(2) Å; b = 7.2688(2) Å; c = 8.2846(2) Å; β = 96.416(2)°; R(I) = 0.0570) have been obtained by solid-state synthesis. Their crystal structures are remarkably dissimilar and underlie a very different magnetic behavior. While PbCu2(SeO3)2Cl2 can be well described by a spin-chain model with an exchange coupling of J1 ≃ 160 K, PbCu2(TeO3)2Cl2 is a spin-dimer system that, however, features a comparable magnetic nearest-neighbor coupling of J ≃ 213 K. PbCu2(SeO3)2Cl2 orders antiferromagnetically below 12 K, whereas PbCu2(TeO3)2Cl2 lacks long-range magnetic order down to at least 2 K, owing to the strong dimerization of the Cu(2+) spins. Crystal structures of both compounds are rationalized in terms of relevant magnetic exchange pathways, and the implications for a broader range of Cu(2+) compounds are discussed.
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- 2013
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34. Cr(VI) trioxide as a starting material for the synthesis of novel zero-, one-, and two-dimensional uranyl dichromates and chromate-dichromates.
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Siidra OI, Nazarchuk EV, Suknotova AN, Kayukov RA, and Krivovichev SV
- Abstract
Six different dichromate-based uranyl compounds were obtained. Their structures belong to four principally different but related structure types with different dimensionality of basic structural units. The units in Cs2(UO2)(Cr2O7)(NO3)2 (1) and (C6H11N2)2(UO2)(Cr2O7)2(H2O) (2) are unique, and these are the first “pure” uranyl-dichromates known to date. The compounds Rb2(UO2)(CrO4)(Cr2O7) (3), (C2NH8)2(UO2)(CrO4)(Cr2O7) (4), (C2NH8)2(UO2)(CrO4)2(Cr2O7)(H2O)2 (5), and (C3NH10)2(UO2)(CrO4)2(Cr2O7)(H2O)2 (6) are novel representatives of a rather small group of inorganic compounds containing both isolated CrO4 tetrahedra and dichromate Cr2O7 groups. The structures of 5 and 6 contain compositionally identical but topologically different ∞(2)[(UO2)(CrO4)2(Cr2O7)](2–) sheets (thus corresponding to different geometrical isomers), which have not been reported previously in inorganic compounds. All novel phases have been prepared with an excess of CrO3. “Pure” dichromates are formed at pH < 1.5 and with prior hydrothermal treatment of uranyl-chromate solution, whereas mixed chromate-dichromates are formed at higher pH > 2 values.
- Published
- 2013
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35. Nanoscale hemispheres in novel mixed-valent uranyl chromate(V,VI), (C3NH10)10[(UO2)13(Cr12(5+)O42)(Cr(6+)O4)6(H2O)6](H2O)6.
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Siidra OI, Nazarchuk EV, Petrunin AA, Kayukov RA, and Krivovichev SV
- Abstract
The structure of a novel mixed-valent chromium uranyl compound, (C(3)NH(10))(10)[(UO(2))(13)(Cr(12)(5+)O(42))(Cr(6+)O(4))(6)(H(2)O)(6)](H(2)O)(6) (1), obtained by the combination of a hydrothermal method and evaporation from aqueous solutions with isopropylammonium, contains uranyl chromate hemispheres with lateral dimensions of 18.9 × 18.5 Å(2) and a height of about 8 Å. The hemispheres are centered by a UO(8) hexagonal bipyramid surrounded by six dimers of Cr(5+)O(5) square pyramids, UO(7) pentagonal bipyramids, and Cr(6+)O(4) tetrahedra. The hemispheres are linked into two-dimensional layers so that two adjacent hemispheres are oriented in opposite directions relative to the plane of the layer. From a topological point of view, the hemispheres have the formula U(21)Cr(23) and can be considered as derivatives of nanospherical cluster U(26)Cr(36) composed of three-, four-, and five-membered rings.
- Published
- 2012
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36. Polytypism and oxo-tungstate polyhedra polymerization in novel complex uranyl tungstates.
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Seliverstov AN, Suleimanov EV, Chuprunov EV, Somov NV, Zhuchkova EM, Lelet MI, Rozov KB, Depmeier W, Krivovichev SV, and Alekseev EV
- Subjects
- Molecular Structure, Polymerization, Tungsten Compounds chemistry, Uranium Compounds chemistry, Tungsten Compounds chemical synthesis, Uranium Compounds chemical synthesis
- Abstract
Three new uranyl tungstates, α-, β-Cs(2)[(UO(2))(2)(W(2)O(9))], and Rb(6)[(UO(2))(7)(WO(5))(2)(W(3)O(13))O(2)], have been obtained by high temperature solid state reactions. All three compounds display novel structure topologies: α- and β-Cs(2)[(UO(2))(2)(W(2)O(9))] are based upon layers with a new topology that can be related to the uranophane topology; Rb(6)[(UO(2))(7)(WO(5))(2)(W(3)O(13))O(2)] is a rare example of a non-molecular inorganic phase with layers containing oxo-tungstate trimers. The structural relationship between α- and β-Cs(2)[(UO(2))(2)(W(2)O(9))] can be assigned to polytypism.
- Published
- 2012
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37. Layered hydrazinium titanate: advanced reductive adsorbent and chemical toolkit for design of titanium dioxide nanomaterials.
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Britvin SN, Lotnyk A, Kienle L, Krivovichev SV, and Depmeier W
- Abstract
LHT-9, a layered hydrazinium titanate with an interlayer spacing of ~9 Å, is a new nanohybrid compound combining the redox functionality of hydrazine, the ion-exchange properties of layered titanate, the large surface area of quasi-two-dimensional crystallites, surface Brønsted acidity, and the occurrence of surface titanyl bonds. LHT-9, ideally formulated as (N(2)H(5))(1/2)Ti(1.87)O(4), relates to a family of lepidocrocite-type titanates. It possesses a high uptake capacity of ~50 elements of the periodic table. Irreversibility of reductive adsorption allows LHT-9 to be used for cumulative extraction of reducible moieties (noble metals, chromate, mercury, etc.) from industrial solutions and wastewaters. Unlike sodium titanates that do not tolerate an acidic environment, LHT-9 is capable of uptake of transition metals and lanthanides at pH > 3. Adsorption products loaded with the desired elements retain their layered structures and can be used as precursors for tailored titanium dioxide nanomaterials. In this respect, the uptake of metal ions by LHT-9 can be considered as a method complementary to electrostatic self-assembly deposition (ESD) and layer-by-layer self-assembly (LBL) techniques. LHT-9 is readily synthesized in one step by a mild fluoride route involving hydrazine-induced hydrolysis of hexafluorotitanic acid under near-ambient conditions.
- Published
- 2011
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38. Murataite-pyrochlore series: a family of complex oxides with nanoscale pyrochlore clusters.
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Krivovichev SV, Yudintsev SV, Stefanovsky SV, Organova NI, Karimova OV, and Urusov VS
- Published
- 2010
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39. Cation ordering and superstructures in natural layered double hydroxides.
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Krivovichev SV, Yakovenchuk VN, Zolotarev AA Jr, Ivanyuk GN, and Pakhomovsky YA
- Subjects
- Cations, Divalent chemistry, Crystallography, X-Ray, Drug Delivery Systems, Metals chemistry, Hydroxides chemistry
- Abstract
Layered double hydroxides (LDHs) constitute an important group of materials with many applications ranging from catalysis and absorption to carriers for drug delivery, DNA intercalation and carbon dioxide sequestration. The structures of LDHs are based upon double brucite-like hydroxide layers [M(2+)(n)M(3+)(m)(OH)(2(m+n)](m+), where M(2+) = Mg(2+), Fe(2+), Mn(2+), Zn(2+), etc.; M(3+) = Al(3+), Fe(3+), Cr(3+), Mn(3+), etc. Structural features of LDHs such as cation ordering, charge distribution and polytypism have an immediate influence upon their properties. However, all the structural studies on synthetic LDHs deal with powder samples that prevent elucidation of such fine details of structure architecture as formation of superstructures due to cation ordering. In contrast to synthetic materials, natural LDHs are known to form single crystals accessible to single-crystal X-ray diffraction analysis, which provides a unique possibility to investigate 3D cation ordering in LDHs that results in formation of complex superstructures, where 2D cation order is combined with a specific order of layer stacking (polytypism). Therefore LDH minerals provide an indispensable source of structural information for modeling of structures and processes happening in LDHs at the molecular and nanoscale levels.
- Published
- 2010
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40. Tricaesium dimolybdate(VI) bromide.
- Author
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Pakhomova AS and Krivovichev SV
- Abstract
The title compound, Cs(3)(Mo(2)O(7))Br, was synthesized by the reaction of CsNO(3), MoO(3) and 1-ethyl-3-methyl-imidazolium bromide. Its crystal structure is isotypic with K(3)(Mo(2)O(7))Br and contains (MoO(4))(2-) tetra-hedra which share an O atom to produce a [Mo(2)O(7)](2-) dimolybdate(VI) anion with a linear bridging angle and m2 symmetry. The anions are linked by Cs atoms (site symmetry m2), forming sheets parallel to (001). Br atoms (site symmetry m2) are also part of this layer. Another type of Cs atom (3m site symmetry) is located in the inter-layer space and connects the layers via Cs-O and Cs-Br inter-actions into a three-dimensional array.
- Published
- 2009
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41. Hexacarbonyl-technetium(I) perchlorate.
- Author
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Gurzhiy VV, Miroslavov AE, Sidorenko GV, Lumpov AA, Krivovichev SV, and Suglobov DN
- Abstract
The title compound, [Tc(CO)(6)]ClO(4), was synthesized by the reaction of [TcCl(CO)(5)] with AgClO(4), followed by acidification with HClO(4) under a CO atmosphere. The [Tc(CO)(6)](+) cation has close to idealized octa-hedral geometry, with the bond angles between cis-CO groups close to 90° and the Tc-C bond lengths in the range 2.025 (3)-2.029 (3)Å. The perchlorate anion is disordered over two crystallographically equivalent half-occupied positions. The Tc atom in the [Tc(CO)(6)](+) cation is located on an inversion centre.
- Published
- 2008
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42. A crown ether as template for microporous and nanostructured uranium compounds.
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Alekseev EV, Krivovichev SV, and Depmeier W
- Published
- 2008
- Full Text
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43. One-dimensional array of two- and three-center cation-cation bonds in the structure of Li4[(UO2)10O10(Mo2O8)].
- Author
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Alekseev EV, Krivovichev SV, Malcherek T, and Depmeier W
- Abstract
Dark-red crystals of the new compound Li(4)[(UO(2))(10)O10(Mo(2)O(8))] (1) have been obtained by high-temperature solid-state reactions. The structure of 1 (monoclinic, P2(1)/c, a = 7.9426(4) A, b = 19.9895(9) A, c = 10.0796(5) A, beta = 90.575(2) degrees, V = 1600.24(13) A(3), Z = 4) consists of a framework of U and Mo polyhedra with Li+ cations in the channels. The framework contains seven-polyhedra-wide uranium oxide tapes interlinked by dimers of edge-sharing [4 + 1]-distorted MoO(5) polyhedra. The U-O tapes are parallel to the a axis, and their planes are oriented parallel to (021) and (02) so that they are cross-linked within the framework. The core of the tapes consists of unprecedented one-dimensional arrays of cation-cation-bonded uranyl ions. The arrays are constructed from eight-membered cycles with uranyl ions linked through two- and three-center cation-cation interactions.
- Published
- 2007
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44. Lead rare-earth oxyhalides: syntheses and characterization of Pb6LaO7X (X = Cl, Br).
- Author
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Siidra OI, Krivovichev SV, Armbruster T, and Depmeier W
- Subjects
- Crystallography, X-Ray, Models, Molecular, Halogens chemistry, Lead chemistry, Metals, Rare Earth chemistry
- Abstract
Yellowish elongated crystals of the two new compounds Pb6LaO7Br (1) and Pb6LaO7Cl (2) have been obtained by the method of solid-state reactions. Both structures can be described in the terms of oxo-centered tetrahedra. The structures of 1 and 2 consist of [O7Pb6La]+ chains that are built from oxocentered OA4 (A = Pb, La) tetrahedra. The halogen ions connect the chains through weak Pb-X bonds. An arrangement of eight OA4 tetrahedra that all share the same central La atom forms a [O8Pb10La3]13+ cluster. The clusters are linked into chains, and additional OPb4 tetrahedra are attached to the chains. Incorporation of Cl atoms instead of Br atoms into the structure causes a lowering of the symmetry from Cmcm to C2/m.
- Published
- 2007
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45. Na2Li8[(UO2)11O12(WO5)2]: Three different uranyl-ion coordination geometries and cation-cation interactions.
- Author
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Alekseev EV, Krivovichev SV, Depmeier W, Siidra OI, Knorr K, Suleimanov EV, and Chuprunov EV
- Subjects
- Cations chemistry, Models, Molecular, Lithium chemistry, Organometallic Compounds chemistry, Sodium chemistry, Tungsten chemistry, Uranium chemistry
- Published
- 2006
- Full Text
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46. Particular topological complexity of lead oxide blocks in Pb31O22X18 (X = Br, Cl).
- Author
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Krivovichev SV, Siidra OI, Nazarchuk EV, Burns PC, and Depmeier W
- Abstract
Dark-green platy crystals of the new compound Pb31O22Br10Cl8 (1) have been obtained by rapid quenching of a lead oxide halide melt. The structure of 1 (triclinic, P1, a = 12.1192(7) angstroms, b = 16.2489(10) angstroms, c = 18.3007(11) angstroms, alpha = 93.104(2) degrees, beta = 95.809(2) degrees, gamma = 111.252(1) degrees, V = 3325.4(3) angstroms3, Z = 2) can be viewed as incorporation of [PbX6]4- halide units (X = Br, Cl) into the defect PbO matrix. The latter represents a two-dimensional [O22Pb30]16+ cationic layer of OPb4 tetrahedra that can be derived from the [OPb] tetrahedral layer observed in tetragonal PbO. The layer consists of 22 symmetrically inequivalent OPb4 tetrahedra and represents the topologically most complicated arrangement of tetrahedra known to date.
- Published
- 2006
- Full Text
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47. Nanoscale tubules in uranyl selenates.
- Author
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Krivovichev SV, Kahlenberg V, Kaindl R, Mersdorf E, Tananaev IG, and Myasoedov BF
- Published
- 2005
- Full Text
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48. Highly porous uranyl selenate nanotubules.
- Author
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Krivovichev SV, Kahlenberg V, Tananaev IG, Kaindl R, Mersdorf E, and Myasoedov BF
- Abstract
A first amine-templated uranyl selenate based upon highly porous uranyl selenate nanotubules, (C4H12N)14[(UO2)10(SeO4)17(H2O)], has been prepared in the room-temperature reaction of uranyl nitrate, butylamine, and H2SeO4 in aqueous solution. The structure consists of nanometer-scale tubular [(UO2)10(SeO4)17(H2O)]14- units packed in a hexagonal-type fashion. The tubules have elliptical cross section with outer dimensions of 25 x 23 A = 2.5 x 2.3 nm. The internal free crystallographic diameter of the tubules is 12.6 A = 1.26 nm, which is comparable to the effective pore size in large-pore zeolites. This finding demonstrates the possibility of nanostructures for actinides in higher oxidation states and opens up a new area of research and exploration.
- Published
- 2005
- Full Text
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49. Crystal structures and cellular automata.
- Author
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Krivovichev SV
- Abstract
Cellular automata are used as dynamic topological models of crystal structures based upon frameworks consisting of fundamental building blocks. Structure is considered as an automaton that works in accord with a prescribed program. Cellular automata models are constructed for metal sulfide frameworks in minerals and compounds of the pentlandite-djerfisherite-bartonite series, for zeolite ACO and compounds with pharmacosiderite structure, leucophosphite, phosphovanadylite etc.
- Published
- 2004
- Full Text
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50. A novel open framework uranyl molybdate: synthesis and structure of (NH4)4[(UO2)5(MoO4)7](H2O)5.
- Author
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Krivovichev SV, Cahill CL, and Burns PC
- Abstract
Single crystals of (NH(4))(4)[(UO(2))(5)(MoO(4))(7)](H(2)O)(5) have been synthesized hydrothermally using (NH(4))(6)Mo(7)O(24), (UO(2))(CH(3)COO)(2).2H(2)O, and H(2)O at 180 degrees C. The phase has been characterized by single-crystal X-ray diffraction using a merohedrally twinned single crystal: it is hexagonal, P6(1), a = 11.4067(5) A, c = 70.659(5) A, V = 7961.9(7) A(3), and Z = 6. The structure is based upon an open framework with composition [(UO(2))(5)(MoO(4))(7)](4-) that is composed of UO(7) pentagonal bipyramids that share vertexes with MoO(4) tetrahedra. The framework has large channels (effective pore size: 4.8 x 4.8 A(2)) parallel to the c axis and a system of smaller channels (effective pore size: 2.5 x 3.6 A(2)) parallel to [100], [110], [010], [110], [110], and [110]. The channels are occupied by NH(4)(+) cations and H(2)O molecules. The topological structure of the uranyl molybdate framework can be described either in terms of fundamental chains of UO(7) pentagonal bipyramids and MoO(4) tetrahedra or in terms of tubular building units parallel to the c axis.
- Published
- 2003
- Full Text
- View/download PDF
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