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66. Švenekite, Ca[AsO2(OH)2]2, a new mineral from Jáchymov, Czech Republic

Author

Ondruš, P., primary, Skála, R., additional, Plášil, J., additional, Sejkora, J., additional, Veselovský, F., additional, Čejka, J., additional, Kallistová, A., additional, Hloušek, J., additional, Fejfarová, K., additional, Škoda, R., additional, Dušek, M., additional, Gabašová, A., additional, Machovič, V., additional, and Lapčák, L., additional

Published
2013
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71. Antiferrodistortive phase transition in EuTiO3

Author

Goian, V., primary, Kamba, S., additional, Pacherová, O., additional, Drahokoupil, J., additional, Palatinus, L., additional, Dušek, M., additional, Rohlíček, J., additional, Savinov, M., additional, Laufek, F., additional, Schranz, W., additional, Fuith, A., additional, Kachlík, M., additional, Maca, K., additional, Shkabko, A., additional, Sagarna, L., additional, Weidenkaff, A., additional, and Belik, A. A., additional

Published
2012
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83. Three tetracoordinate Co(ii) complexes [Co(biq)X2] (X = Cl, Br, I) with easy-plane magnetic anisotropy as field-induced single-molecule magnets.

Author

Smolko, L., Černák, J., Dušek, M., Miklovič, J., Titiš, J., and Boča, R.

Subjects
MICROMAGNETICS, MAGNETIC materials, SINGLE molecule magnets, MAGNETIC properties, LIGANDS (Chemistry)
Abstract

Three mononuclear complexes [Co(biq)X2] (biq = 2,2′-biquinoline; X = Cl, Br, I) were prepared by a solvothermal method and characterized by single-crystal X-ray diffraction. In all three complexes the Co(ii) atom is tetrahedrally coordinated by one biq ligand bonded in a chelate manner and two halogenido ligands. Hydrogen bonding interactions (C–H…X) along with the π–π interactions contribute to the stability of the formed packing. Magnetic measurements as well as ab initio calculations revealed that the complexes possess a sizable easy-plane magnetic anisotropy (D ＞ 0). They display a superparamagnetic behaviour in an applied external field that culminates between BDC = 0.2–0.3 T. Two relaxation processes are observed; the faster can be analysed in terms of the direct and Orbach processes yielding U/kB = 42.6 K and τ0 = 1.9 × 10−10 s for X = Cl, U/kB = 39.6 K and τ0 = 1.2 × 10−10 s for X = Br and U/kB = 57.0 K and τ0 = 3.2 × 10−13 s for X = I at BDC = 0.2 T. [ABSTRACT FROM AUTHOR]

Published
2015
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88. Synthesis and crystal structure of a new N-(2,6-dichlorobenzoyl)- N′, N″-bis(pyrrolidinyl)-phosphoric triamide as a carrier and competitive bulk liquid membrane transport of six metal cations.

Author

Khoshnood, Razieh, Pourayoubi, Mehrdad, Kasraee, Farideh, Toghraee, Maryam, Dušek, M., and Bereciartua, P.

Abstract

The competitive metal ion transport experiments of Co, Cd, Ag, Pb, Ni, and Cu were carried out by N-(2,6-dichlorobenzoyl)- N′, N″-bis(pyrrolidinyl)-phosphoric triamide as a carrier in organic membrane phase. 2,6-ClCHC(O)NHP(O)[NCH] has been synthesized and characterized by mass spectrometry IR spectroscopy and single crystal X-ray diffraction. The asymmetric unit of title phosphoric triamide contains one symmetrically independent molecule. The source phase contained equimolar concentrations of metal ions at pH 5 and the receiving phase being buffered at pH 3. The following solvents were examined as membrane: chloroform (CHCl), nitrobenzene (NB), 1,2-dichloroethane (1,2-DCE), dichloromethane (DCM), dichloromethane/1,2-dichloroethane (DCM/1,2-DCE). The obtained results show that the selectivity and efficiency of transport for these heavy metal cations change with the nature of the ligand and also the organic solvents, which were used as liquid membrane in these experiments. A good selectivity was observed for Pb cation by this ligand in all membrane systems. Moreover, the selectivity of metal cations in DCM is higher than other solvents. A non-linear relationship was found between the percent of transport of Pb cation by this ligand and the compositions of DCM/1,2-DCE and binary solution by this ligand. The effect of several factors such as the nature of carboxylic acids (stearic, fumaric and maleic acid) as surfactant in the membrane phase and the time of transport on transport efficiency of Pb cation were investigated. [ABSTRACT FROM AUTHOR]

Published
2014
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93. The crystal structure of franckeite, Pb21.7Sn9.3Fe4.0Sb8.1S56.9.

Author

Makovicky, E., Petřiček, V., Dušek, M., and Topa, D.

Subjects
LEAD compounds, MOLECULAR structure, SULFIDES, PARTICLES (Nuclear physics), WAVES (Physics)
Abstract

The layer-like crystal structure of franckeite from the mine of San José, Bolivia, exhibits a pronounced one-dimensional transversal wave-like modulation and a non-commensurate layer match in two dimensions. It consists of alternating pseudohexagonal (H) layers and pseudotetragonal (Q) slabs and forms a homologous pair with cylindrite, which has thinner Q slabs. The Q slabs in franckeite are four atomic layers thick. The two components have their own lattices and a common modulation. The Q slab of the refined franckeite structure, Pb21.74Sn9.34Fe3.95Sb8.08S56.87, is an MS layer (M = Pb2+, Sn2+, Sb3+) four atomic planes thick, with a = 5.805(8), b = 5.856(16) Å, and the layer-stacking vector c = 17.338(5) Å. The lattice angles are α = 94.97(2)°, β = 88.45(2)°, γ = 89.94(2)°; the modulation vector q = --0.00129(8) a* + 0.128436(10) b* -- 0.0299(3) c*. The H layer is a single-octahedron MS2 layer (M = Sn4+, Fe2+) with a = 3.665(8), b = 6.2575(16), c = 17.419(5) Å, α = 95.25(2)°, β = 95.45(2)°, γ = 89.97(2)°; the modulation vector is q = --0.00087(8) a* + 0.13725(16) b* -- 0.0314(4) c*. The a and b vectors of both subsystems are parallel; the c vectors diverge. (3+2)D superspace refinement was performed in the superspace group C1̅1, using 7397 observed reflections. It resulted in the overall R(obs) value equal to 0.094. The Q slabs are composed of two tightly bonded double-layers, separated by an interspace hosting non-bonding electron pairs. Average composition of cations on the outer surface was refined as Pb0.74 (Sn,Sb)0.26, whereas that of cations, which are adjacent to the interspace with lone electron pairs, with a configuration analogous to that observed in orthorhombic SnS, corresponds to (Sn,Sb) 0.73Pb0.27. Iron is dispersed over the octahedral Sn4+ sites in the H layer. Transversal modulation of the Q slab is achieved by local variations in the Pb:(Sn,Sb) ratios at its surface and interior. Its purpose is to re-establish a one-dimensional commensurate contact along [010] between the curved Q and H surfaces to the greatest extent possible. Layer-stacking disorder and divergence of the Q and H stacking directions, and the divergence between modulation wave-front and these stacking directions are typical for the composite structures of franckeite and cylindrite. Because of the increased rigidity of the Q component, franckeite usually forms masses of curved crystals rather than cylindrical aggregates. The existence of this family depends critically on the radius ratios of the cations involved, especially those involving (Pb2+, Sn2+) and Sn4+. Their replacement by a Pb2+:Bi3+ combination leads to misfit layer structures of a very different type, typified by cannizzarite. [ABSTRACT FROM AUTHOR]

Published
2011
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94. Synthesis and characterization of single crystals of the layered copper hydroxide acetate Cu2(OH)3(CH3COO)·H2O.

Author

Švarcová, S., Klementová, M., Bezdička, P., Łasocha, W., Dušek, M., and Hradil, D.

Abstract

Single-crystals of the layered copper hydroxide acetate Cu2(OH)3(CH3COO)·H2O were synthesized by heating copper acetate solution at 60 °C. The standard synthesis of the title compound based on slow titration of copper acetate solution with NaOH yielded materials with worse morphology and an additional phase present. The obtained products were characterized with powder X-ray diffraction, high temperature powder X-ray diffraction, scanning electron microscopy and infrared spectroscopy. The crystal structure was determined from single-crystal X-ray diffraction data, collected both at 120 K and at 293 K. The title compound crystallizes in the monoclinic botallackite-type layered structure, space group P 21, with the lattice parameters a = 5.5776(3) Å, b = 6.0733(2) Å, c = 18.5134(8) Å, β = 91.802(4)° and a = 5.5875(4)Å, b = 6.0987(4) Å, c = 18.6801(10)Å, β = 91.934(5)° for 120 K and for 293 K, respectively. Acetate groups and water molecules are interlayered between corrugated sheets of edge-sharing CuO6 octahedra exhibiting strong distortion resulted from the Jahn-Teller effect. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Published
2011
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95. The crystal structure of franckeite, Pb21.7Sn9.3Fe4.0Sb8.1S56.9

Author

Makovicky, E., Petříček, V., Dušek, M., and Topa, D.

Abstract

The layer-like crystal structure of franckeite from the mine of San José, Bolivia, exhibits a pronounced one-dimensional transversal wave-like modulation and a non-commensurate layer match in two dimensions. It consists of alternating pseudohexagonal (H) layers and pseudotetragonal (Q) slabs and forms a homologous pair with cylindrite, which has thinner Q slabs. The Q slabs in franckeite are four atomic layers thick. The two components have their own lattices and a common modulation. The Q slab of the refined franckeite structure, Pb21.74Sn9.34Fe3.95Sb8.08S56.87, is an MS layer (M = Pb2+, Sn2+, Sb3+) four atomic planes thick, with a = 5.805(8), b = 5.856(16) Å, and the layer-stacking vector c = 17.338(5) Å. The lattice angles are α = 94.97(2)°, β = 88.45(2)°, γ = 89.94(2)°; the modulation vector q = -0.00129(8) a* + 0.128436(10) b* - 0.0299(3) c*. The H layer is a single-octahedron MS2layer (M = Sn4+, Fe2+) with a = 3.665(8), b = 6.2575(16), c = 17.419(5) Å, α = 95.25(2)°, β = 95.45(2)°, γ = 89.97(2)°; the modulation vector is q = -0.00087(8) a* + 0.13725(16) b* - 0.0314(4) c*. The a and b vectors of both subsystems are parallel; the c vectors diverge. (3+2)D superspace refinement was performed in the superspace group C1, using 7397 observed reflections. It resulted in the overall R(obs) value equal to 0.094. The Q slabs are composed of two tightly bonded double-layers, separated by an interspace hosting non-bonding electron pairs. Average composition of cations on the outer surface was refined as Pb0.74(Sn,Sb)0.26, whereas that of cations, which are adjacent to the interspace with lone electron pairs, with a configuration analogous to that observed in orthorhombic SnS, corresponds to (Sn,Sb)0.73Pb0.27. Iron is dispersed over the octahedral Sn4+sites in the H layer. Transversal modulation of the Q slab is achieved by local variations in the Pb:(Sn,Sb) ratios at its surface and interior. Its purpose is to re-establish a one-dimensional commensurate contact along [010] between the curved Q and H surfaces to the greatest extent possible. Layer-stacking disorder and divergence of the Q and H stacking directions, and the divergence between modulation wave-front and these stacking directions are typical for the composite structures of franckeite and cylindrite. Because of the increased rigidity of the Q component, franckeite usually forms masses of curved crystals rather than cylindrical aggregates. The existence of this family depends critically on the radius ratios of the cations involved, especially those involving (Pb2+, Sn2+) and Sn4+. Their replacement by a Pb2+:Bi3+combination leads to misfit layer structures of a very different type, typified by cannizzarite.

Published
2011
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97. Crystal structure of a synthetic tin-selenium representative of the cylindrite structure type

Author

Makovicky, E., Petříček, V., Dušek, M., and Topa, D.

Abstract

The synthetic tin-selenium member of the cylindrite structural family, with the empirical formula Sn31.52Sb6.23Fe3.12S59.12based on electron-microprobe data, has a triclinic crystal structure composed of two alternating layer types, both with a pronounced one-dimensional modulation, and with a noncommensurate layer match in two dimensions. The pseudotetragonal (Q) layer is a MeSe layer twoatomic planes thick with lattice parameters a = 5.969(2) Å, b = 6.004(1) Å, and the layer-stacking vector c = 12.238(1) Å, α = 87.98(4)°, β = 83.14(3)°, and γ = 90.01(4)°. The pseudohexagonal (H) layer is a single-octahedral MeSe2layer with a = 3.831(1) Å, b = 6.580(3) Å, c = 12.151(5) Å, α = 87.79(4)°, β = 90.59(3)°, and γ = 89.99(3)°; the a and b vectors of the two subsystems are parallel, the c vectors diverge. The transversal wave-like modulation has the wave-normal parallel to b, so that the modulation vector q is 0.0001(3) a* + 0.1921(4) b* - 0.0119(3) c* in terms of the pseudohexagonal subsystem. Superspace structure refinement in the superspace group X1̄ where X stands for non-primitive centering vectors (½,½,0,0,0), (0,0,0,0,½), (½,½,0,0,½) in five-dimensional superspace, and based on 2128 observed reflections, resulted in R1 = 0.038 for all reflections. Composition of the H layer has been modeled as Sn4+240Fe2+54Se588, that of the Q layer as Sn2+306Sb3+108Se414. The cation-anion distances in the Q layer vary between 2.63 and 3.30 Å, indicating that the cations present are primarily Sn2+(and Sb3+), whereas distances in the H layer lie between 2.665 and 2.721 Å and correspond to Sn4+with admixture of Fe2+. The shortest cation-anion distance across the interlayer space is 3.24 Å. Relations between layer match and the modulation vector, divergence of layer stackings of the two components, and reasons for the modulation and for the pronounced disorder of the Q component, as well as the differences and similarities with levyclaudite, franckeite, and synthetic layer-misfit compounds are discussed in detail. In its structural principles, although not in numerical values, the Sn-Se cylindrite corresponds fully to the natural Pb-Sn-S cylindrite previously described.

Published
2008
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