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Crystalline Systems (crystalline + system)
Selected AbstractsA Crystalline Phase Transition and Optical Properties in a CoIICuII Oxamato-Bridged Ferrimagnetic ChainEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2005Cynthia L. M. Pereira Abstract The compound [CoCu(opba)(DMSO)3] (1) [opba = ortho -phenylenebis(oxamato)] has been synthesized and characterized. Its crystal structure has been analyzed by X-ray diffraction techniques at 100 and 298 K. A structural phase-transition has been detected at around 150 K. An orthorhombic crystalline system is found at both temperatures, with very similar unit-cell dimensions. At room temperature 1 crystallizes in the Pnam space group (, -1 phase), with a = 7.6712(2), b = 14.8003(3), c = 21.0028(5) Ĺ, and Z = 4, whereas at low temperature it crystallizes in the Pna21 space group (, -1 phase), with a = 7.3530(2), b = 14.5928(4), c = 21.0510(7) Ĺ, and Z = 4. Both crystalline phases consist of linearly ordered bimetallic chains with the [Cu(opba)]2, units tied by CoII ions to form a one-dimensional system. The DMSO molecules in , -1, which are coordinated to either CuII or CoII, are disordered. At low temperature, a small reorganization of the CuII and CoII environments is observed. The origin of this phase transition, which is completely reversible, is the modification of the crystalline packing with the temperature. Linear birefringence measurements were done on single crystals in the 100,300 K temperature range. Around 150 K, the linear birefringence curve shows an inflexion that is interpreted as being related to the conversion of ,-1 into , -1. Both dc and ac magnetic measurements were performed on the polycrystalline sample. The results reveal a one-dimensional ferrimagnetic behavior. Single crystal optical characterization at room temperature shows that 1 presents a very strong dichroism superposed on the linear birefringence. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis and characterizations of nanosized iron(II) hydroxide and iron(II) hydroxide/poly(vinyl alcohol) nanocompositeJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010M. Fathima Parveen Abstract Nanosized Fe(OH)2 was synthesized by a coprecipitation method. Peaks between 500 and 1250 cm,1 in Fourier transform infrared (FTIR) spectroscopy confirmed the presence of metal hydroxide stretching. X-ray diffraction showed the suppressed crystalline system of Fe(OH)2/aniline (ANI) due to the presence of a higher weight percentage of the dispersing agent, ANI. Thermogravimetric analysis implied that 75.5 wt % of residue remained up to 800°C. High resolution transmission electron microscope (HRTEM) analysis of Fe(OH)2/ANI revealed that its size ranged from 10 to 50 nm with a rodlike morphology. Scanning electron microscopy implied that pristine Fe(OH)2 had a nanotriangular platelet morphology, and a higher weight percentage of dispersing agent intercalated with Fe(OH)2 had a spheroid with an agglomerated structure. The (UV,visible) spectrum implied the presence of Fe2+ ions at 326 nm and the existence of an amino group intercalated with Fe(OH)2 showed a sharp peak at 195 nm, the intensity of which increased with increasing intercalated dispersing agent weight percentage. Photoluminescence showed that ANI-intercalated Fe(OH)2 showed a lesser intensity than the pristine Fe(OH)2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] ISAACS, interactive structure analysis of amorphous and crystalline systemsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2010Sébastien Le Roux ISAACS (interactive structure analysis of amorphous and crystalline systems) is a cross-platform program developed to analyze the structural characteristics of three-dimensional structure models built by computer simulations. The models may have any degree of periodicity (i.e. crystallinity) and local symmetry. The following structural information is computed from the models: total and partial radial distribution functions and structure factors for X-ray or neutron scattering, coordination numbers, bond-angle and near atomic neighbor distributions, bond-valence sums, ring statistics, and spherical harmonics invariants. The information may be visualized conveniently and stored for further use. [source] Diffraction line profiles from polydisperse crystalline systemsACTA CRYSTALLOGRAPHICA SECTION A, Issue 5 2001Paolo Scardi Diffraction patterns for polydisperse systems of crystalline grains of cubic materials were calculated considering some common grain shapes: sphere, cube, tetrahedron and octahedron. Analytical expressions for the Fourier transforms and corresponding column-length distributions were calculated for the various crystal shapes considering two representative examples of size-distribution functions: lognormal and Poisson. Results are illustrated by means of pattern simulations for a f.c.c. material. Line-broadening anisotropy owing to the different crystal shapes is discussed. The proposed approach is quite general and can be used for any given crystallite shape and different distribution functions; moreover, the Fourier transform formalism allows the introduction in the line-profile expression of other contributions to line broadening in a relatively easy and straightforward way. [source] | ||||||||||