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Monoclinic Cell (monoclinic + cell)
Selected AbstractsPseudomerohedrally twinned monoclinic structure of unfolded `free' nonactin: comparative analysis of its large conformational change upon encapsulation of alkali metal ionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009Ilia A. Guzei The title compound, C40H64O12, crystallizes in a pseudomerohedrally twinned primitive monoclinic cell with similar contributions of the two twin components. There are two symmetry-independent half-molecules of nonactin in the asymmetric unit. Each molecule has a pseudo- S4 symmetry and resides on a crystallographic twofold axis; the axes pass through the molecular center of mass and are perpendicular to the plane of the macrocycle. The literature description of the room-temperature structure of nonactin as an order,disorder structure in an orthorhombic unit cell is corrected. We report a low-temperature high-precision ordered structure of `free' nonactin that allowed for the first time precise determination of its bond distances and angles. It possesses an unfolded and more planar geometry than its complexes with encapsulated Na+, K+, Cs+, Ca2+ or NH4+ cations that exhibit more isometric overall conformations. [source] The centrosymmetric metal metaborate KCdB3O6ACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2009Shifeng Jin The title compound, potassium cadmium metaborate, crystallizes in a monoclinic cell, featuring infinite one-dimensional CdO5 chains and trigonal planar B atoms in hexagonal B3O6 metaborate ions. The trigonal bipyramidal CdO5 chains and metaborate ions are interlinked to form a three-dimensional framework, creating channels running parallel to the [10] direction in which the potassium ions reside. [source] The new pentaborate Na3SrB5O10ACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2008Li Wu Sodium strontium pentaborate, Na3SrB5O10, maintains the same, previously unobserved, structure type at 200, 250 and 293,K. The fundamental building units are anionic [B5O10]5, groups distorted from mm2 point symmetry. The Sr atoms are eightfold coordinated by O atoms, forming trigonal dodecahedra. The Na atoms appear in three crystallographically different environments. The present single-crystal results correct a previous report in which a monoclinic cell was deduced for this compound on the basis of powder diffraction data. The structure of the title compound is discussed in the crystalochemical context of other borates with the same formula type. Although the unit cell of the present compound is similar to that determined in a previous study of the analogous Ca-containing compound, this study demonstrates that the structures of the two are different. These novel alkali,alkaline earth borates are considered as potential host materials for optical applications (fluorescence materials or phosphors). [source] A New Oxide Ion Conductor: La3GaMo2O12CHINESE JOURNAL OF CHEMISTRY, Issue 8 2006Tian Xia Abstract A new oxide ion conductor, La3GaMo2O12, with a bulk conductivity of 2.7×10,2 S·cm,1 at 800 °C in air atmosphere was prepared by the traditional solid-state reaction. The room temperature X-ray diffraction data could be indexed on a monoclinic cell with lattice parameters of a=0.5602(2) nm, b=0.3224(1) nm, c=1.5741(1) nm, ,=102.555(0)°, V=0.2775(2) nm3 and space group Pc(7). Ac impedance measurements in various atmospheres further support that it is an oxide ion conductor. This material was stable in various atmospheres with oxygen partial pressure p(O2) ranging from 1.0×105 to 1.0×10,7 Pa at 800 °C. A reversible polymorphic phase transition occurred at elevated temperatures as confirmed by the differential thermal analysis and dilatometric measurement. [source] | ||||||||||