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Biomedical subjects

Sergey V Krivovichev

Publications and source records attributed to Sergey V Krivovichev.

6 recordsLinked to original sources
PubMed2006

Particular topological complexity of lead oxide blocks in Pb31O22X18 (X = Br, Cl).

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.

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PubMed2005

Highly porous uranyl selenate nanotubules.

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.

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PubMed2004

Crystal structures and cellular automata.

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.

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PubMed2002

Synthesis and structure of Ag(6)[(UO(2))(3)O(MoO(4))(5)]: a novel sheet of triuranyl clusters and MoO(4) tetrahedra.

The new uranyl molybdate Ag(6)[(UO(2))(3)O(MoO(4))(5)] (1) with an unprecedented uranyl molybdate sheet has been synthesized at 650 degrees C. The structure (monoclinic, C2/c, a = 16.4508(14) A, b = 11.3236(14) A, c = 12.4718(13) A, beta = 100.014(4)(o), V = 2337.4(4) A(3), Z = 4) contains [(UO(2))(3)O(MoO(4))(5)] sheets composed of triuranyl [(UO(2))(3)O] clusters that are connected by MoO(4) tetrahedra. The topology of the uranyl molybdate sheet in 1 represents a major departure from sheets observed in other uranyl compounds. Of the approximately 120 known inorganic uranyl compounds containing sheets of polyhedra, 1 is the only structure that contains trimers of uranyl pentagonal bipyramids that are connected only by the sharing of vertexes with other polyhedra. The sheets are parallel to (001) and are linked by Ag cations.

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