Crystal structure of fully dehydrated fully TI+ -exchanged zeolite X
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Sodalite
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The crystal and molecular structure of the title compound has been determined by single-crystal X-ray analysis and refined to an R value of 0.027. The crystal is monoclinic, space group P21/c with a= 5.476(3), b= 14.540(7), c= 6.915(3)Å, β= 99.88(4)°, and Z= 2. The structure consists of layers of dipositive cations [C4H12N8]2+ and Cl– ions. The planar cation has the trans-configuration of the chain. Hydrogen bonds of the type N–H ⋯ Cl– are formed within the layers, but not between them. The molecules in the crystal are held together through stacking and via the delocalized π-electron system. The mean planes of the cations are approximately 3.51 Å apart. The crystal structure is compared with that of other bis(amidinohydrazone) derivatives and the relationship between crystal structure and biochemical properties is discussed.
Monoclinic crystal system
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Glyoxal
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Monoclinic crystal system
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Monoclinic crystal system
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Angstrom
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Monoclinic crystal system
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Sodalite
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Polycrystalline U3O7 powder was synthesized by oxidation of UO2 powder under controlled conditions using in situ thermal analysis, and by heat treatment in a tubular furnace. The O/U ratio of the U3O7 phase was measured as 2.34 ± 0.01. The crystal structure was assessed from X-ray diffraction (XRD) and selected-area electron diffraction (SAED) data. Similar to U4O9-ε (more precisely U64O143), U3O7 exhibits a long-range ordered structure, which is closely related to the fluorite-type arrangement of UO2. Cations remain arranged identical to that in the fluorite structure, and excess anions form distorted cuboctahedral oxygen clusters, which periodically replace the fluorite anion arrangement. The structure can be described in an expanded unit cell containing 15 fluorite-like subcells (U15O35), and spanned by basis vectors A = ap - 2bp, B = -2ap + bp, and C = 3cp (lattice parameters of the subcell are ap = bp = 538.00 ± 0.02 pm and cp = 554.90 ± 0.02 pm; cp/ap = 1.031). The arrangement of cuboctahedra in U3O7 results in a layered structure, which is different from the well-known U4O9-ε crystal structure.
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Triclinic crystal system
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The structure of a single crystal, grown by a slow cooling a melt of $Ca_{1.29}Bi_{0.14}VO_4$ composition, was analyzed. The crystals belong to the rhombohedral space group R3c and the dimensions of the unit cells are a = 10.848(1)${\AA}$ , c = 38.048(6)${\AA}$ , V = 3877.6(8)${\AA}^3$ for the pale yellow crystal, and a = 10.857(1), c = 38.063(6)${\AA}$ , V = 3885.6(8)${\AA}^3$ for the yellow crystal, respectively. Unit cell dimensions of the crystal were larger than those of the host crystal, $Ca_3(VO_4)_2$ , owing to the Bi that replaced Ca in the unit cell. Ca in the unit cell formed six, eight and nine coordinated polyhedra with O atoms and Bi replacing Ca entered the eight or nine coordinated Ca sites with different crystallographic environments in the unit cell. All the V in the unit cell formed four coordinated tetrahedra with O atoms, however V-O bond lengths in the tetrahedra were different from one another.
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The crystal sructures of and dehydrated at and Torr have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at Their structures were refined to the final error indices, with 166 reflections, and with 130 reflections, respectively, for which I > In dehydrated ions are located at two different sites opf high occupancies. Sixteen ions are located at site I, the centers of the double six rings and thirty ions are located at site II, the six-membered ring faces of sodalite units in the supercage. Latter ions are recessed into the supercage from the three O(2) oxygen plane (Ca(2)-O(2)= and In the structure of , all ions and ions are located at the four different crystallographic sites: 16 ions are located in the centers of the double six rings, another sixteen ions and sixteen ions are located at the site II in the supercage. These ions adn ions are recessed and , respectively, into the supercage from their three O(2) oxygen planes , , , and Twelve ions lie at the site III, twofold axis of edge of the four-membered ring ladders inside the supercage and
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