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X-ray Powder Diffraction Patterns (x-ray + powder_diffraction_pattern)
Selected AbstractsStructural study of the semimagnetic semiconductor Zn0.5Mn0.5In2Te4CRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2009G. E. Delgado Abstract The semimagnetic semiconductor alloy Zn0.5Mn0.5In2Te4 was refined from an X-ray powder diffraction pattern using the Rietveld method. This compound crystallizes in the space group I42m (Nº 121), Z = 2, with unit cell parameters a = 6.1738(1) Å, c = 12.3572(4) Å, V = 471.00(2) Å3, c/a = 2.00. This material crystallizes in a stannite-type structure. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Crystal structure prediction of organic pigments: quinacridone as an exampleJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2007N. Panina The structures of the ,, , and , polymorphs of quinacridone (Pigment Violet 19) were predicted using Polymorph Predictor software in combination with X-ray powder diffraction patterns of limited quality. After generation and energy minimization of the possible structures, their powder patterns were compared with the experimental ones. On this basis, candidate structures for the polymorphs were chosen from the list of all structures. Rietveld refinement was used to validate the choice of structures. The predicted structure of the , polymorph is in accordance with the experimental structure published previously. Three possible structures for the , polymorph are proposed on the basis of X-ray powder patterns comparison. It is shown that the , structure in the Cambridge Structural Database is likely to be in error, and a new , structure is proposed. The present work demonstrates a method to obtain crystal structures of industrially important pigments when only a low-quality X-ray powder diffraction pattern is available. [source] Classification of stacking faults and their stepwise elimination during the disorder , order transformation of nickel hydroxideACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2006T. N. Ramesh Nickel hydroxide samples obtained by strong alkali precipitation are replete with stacking faults. The local structures of the stacking faults resemble the stacking patterns of different polytypic modifications that are theoretically possible among the layered hydroxides. This resemblance becomes a basis for the classification of stacking faults into different types. Each type of stacking fault produces a characteristic non-uniform broadening of peaks in the X-ray powder diffraction pattern of nickel hydroxide. DIFFaX simulations aid the classification and quantification of stacking faults. Hydrothermal treatment of a poorly ordered nickel hydroxide slurry at different temperatures (338,473,K) and different durations (5,48,h) shows that the stacking faults are removed in a stepwise manner. The as-precipitated sample has 17,20% stacking faults of the 3R2 variety, which evolve into the 2H2 type at 413,K. The 2H2 stacking faults persist up to 443,K. The stacking faults are completely removed only at 473,K. At this temperature an ordered ,-Ni(OH)2 phase is observed. [source] In-house characterization of protein powderJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2010Christian Grundahl Hartmann X-ray powder diffraction patterns of lysozyme and insulin were recorded on a standard in-house powder diffractometer. The experimental powder diffraction patterns were compared with patterns calculated from Protein Data Bank coordinate data. Good agreement was obtained by including straightforward corrections for background, unit-cell parameters, disordered bulk solvent and geometric factors. In particular the solvent correction was found crucial for a good agreement. A revised Lorentz factor was derived, which gave a minor, but significant, improvement to the fit in the low-angle region. An attempt to include calculated H-atom positions did not improve the overall fit and was abandoned. The method devised was shown to be a quick and convenient tool for distinguishing precipitates and polymorphs of proteins. [source] Crystal structure prediction of organic pigments: quinacridone as an exampleJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2007N. Panina The structures of the ,, , and , polymorphs of quinacridone (Pigment Violet 19) were predicted using Polymorph Predictor software in combination with X-ray powder diffraction patterns of limited quality. After generation and energy minimization of the possible structures, their powder patterns were compared with the experimental ones. On this basis, candidate structures for the polymorphs were chosen from the list of all structures. Rietveld refinement was used to validate the choice of structures. The predicted structure of the , polymorph is in accordance with the experimental structure published previously. Three possible structures for the , polymorph are proposed on the basis of X-ray powder patterns comparison. It is shown that the , structure in the Cambridge Structural Database is likely to be in error, and a new , structure is proposed. The present work demonstrates a method to obtain crystal structures of industrially important pigments when only a low-quality X-ray powder diffraction pattern is available. [source] Dehydration studies using a novel multichamber microscale fluid bed dryer with in-line near-infrared measurementJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2003Eetu Räsänen Abstract The purpose of this research was to study the effect of two process parameters (temperature and moisture content) on dehydration behavior of different materials using a novel multichamber microscale fluid bed dryer with a process air control unit and in-line near-infrared (NIR) spectroscopy. The materials studied were disodium hydrogen phosphates with three different levels of hydrate water and wet theophylline granules. Measured process parameters of fluid bed drying were logged, including in-line NIR signals. Off-line analyses consisted of X-ray powder diffraction patterns, Fourier transform NIR spectra and moisture contents of studied materials. During fluid bed drying, the stepwise dehydration of materials was observed by the water content difference of inlet and outlet air, the pressure difference over the bed, and the in-line NIR spectroscopy. The off-line analysis confirmed the state of solid materials. The temperature and the moisture content of the process air were demonstrated to be significant factors for the solid-state stability of theophylline. The presented setup is a material and cost-saving approach for studying the influence of different process parameters on dehydration behavior during pharmaceutical processing. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:2074,2081, 2003 [source] Low-Loss Microwave Dielectrics Using Mg2(Ti1,xSnx)O4 (x=0.01,0.09) Solid SolutionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009Cheng-Liang Huang Low-loss ceramics having the chemical formula Mg2(Ti1,xSnx)O4 for x ranging from 0.01 to 0.09 have been prepared by the conventional mixed oxide route and their microwave dielectric properties have been investigated. X-ray powder diffraction patterns indicate the corundum-structured solid solutions for the prepared compounds. In addition, lattice parameters, which linearly increase from 8.4414 to 8.4441 Å with the rise of x from 0.01 to 0.09, also confirm the forming of solid solutions. By increasing x from 0.01 to 0.05, the Q×f of the specimen can be tremendously boosted from 173 000 GHz to a maximum 318 000 GHz. A fine combination of microwave dielectric properties (,r,15.57, Q×f,318 000 GHz at 10.8 GHz, ,f,,45.1 ppm/°C) was achieved for Mg2(Ti0.95Sn0.05)O4 ceramics sintered at 1390°C for 4 h. Ilmenite-structured Mg(Ti0.95Sn0.05)O3 (,r,16.67, Q×f,275 000 GHz at 10.3 GHz, ,f,,53.2 ppm/°C) was detected as a second phase. The presence of the second phase, however, would cause no significant variation in the dielectric properties of the specimen, because the second phase properties are very similar to the primary phase. These unique properties, in particular, low ,r and high Q×f, can be utilized as a very promising dielectric material for ultra-high-frequency applications. [source] Nitridation of Silica to an ,-Silicon Nitride Nanorod Using NaNH2 in the Autoclave at 700°CJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007Lingling Zhu ,-silicon nitride nanorods have been synthesized through solid-state reduction,nitridation of silica using NaNH2 as both a reductant and a nitriding reagent. X-ray powder diffraction patterns show that the products have a hexagonal phase with lattice parameters a=7.767 Å and c=5.630 Å. Transmission electron microscopy reveals that the as-synthesized products are pure nanorods with an average size about 30 nm in diameter and 400 nm in length. X-ray photoelectron spectra indicate that the molar ratio of Si/N is 2.988:4. Fourier-transform infrared spectrum yields a strong Si,N absorption at 926 cm,1 that may be a red shift due to size effect. [source] Rietveld analysis of X-ray powder diffraction patterns as a potential tool for the identification of impact-deformed carbonate rocksMETEORITICS & PLANETARY SCIENCE, Issue 11 2009Sarah A. Huson Entire XRD patterns, single peak profiles and Rietveld refined parameters of carbonate samples from the Sierra Madera impact crater, west Texas, unshocked equivalent samples from 95 miles north of the crater and the Mission Canyon Formation of southwest Montana and western Wyoming were used to evaluate the use of X-ray powder diffraction as a potential tool for distinguishing impact deformed rocks from unshocked and tectonically deformed rocks. At Sierra Madera dolostone and limestone samples were collected from the crater rim (lower shock intensity) and the central uplift (higher shock intensity). Unshocked equivalent dolostone samples were collected from well cores drilled outside of the impact crater. Carbonate rocks of the Mission Canyon Formation were sampled along a transect across the tectonic front of the Sevier and Laramide orogenic belts. Whereas calcite subjected to significant shock intensities at the Sierra Madera impact crater can be differentiated from tectonically deformed calcite from the Mission Canyon Formation using Rietveld refined peak profiles, weakly shocked calcite from the crater rim appears to be indistinguishable from the tectonically deformed calcite. In contrast, Rietveld analysis readily distinguishes shocked Sierra Madera dolomite from unshocked equivalent dolostone samples from outside the crater and tectonically deformed Mission Canyon Formation dolomite. [source] Inverse bilayer structure of mononuclear CoII and NiII complexes of the type M(H2O)3(SO4)(4-CNpy)2ACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2009Birinchi K. Das Two new metal compounds of the formula [M(H2O)3(SO4)(4-CNpy)2]·H2O [M = Ni (1) and Co (2), 4-CNpy = 4-cyanopyridine] have been prepared and studied by X-ray diffraction. In both of these compounds the 4-CNpy ligands are coordinated via pyridyl-N atoms to the metal ions in a cis fashion. The neutral complexes along with the uncoordinated H2O molecules are glued together preferentially into inverse bilayers by non-covalent interactions, including unique interlayer ,,, interactions between antiparallel nitrile groups. Hartree,Fock and density-functional theory (DFT) calculations indicate that the ,,, interactions are energetically significant. The unit-cell similarity index (,) of 0.0046 for the compounds suggests their isostructurality, which is also supported by their X-ray powder diffraction patterns that can be almost superimposed. [source] X-ray powder diffraction and electron diffraction studies of the thortveitite-related L phase, (Zn,Mn)2V2O7ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2009Kevin M. Knowles The phase designated ,-Zn3(VO4)2 reported as a minor second phase in zinc oxide-based varistor materials doped with vanadium oxide and manganese oxide is shown to be the L phase, (Zn1,,,xMnx)2V2O7 (0.188 < x < 0.538), in the pseudo-binary Mn2V2O7,Zn2V2O7 system. Analysis of X-ray powder diffraction patterns and electron diffraction patterns of this phase shows that the previously published a, c and , values for this thortveitite-related phase are incorrect. Instead, Rietveld refinement of the X-ray powder pattern of the L phase shows that it has a monoclinic C lattice with Z = 6, with a = 10.3791,(1), b = 8.5557,(1), c = 9.3539,(1),Å and , = 98.467,(1)°. Although prior convergent-beam electron diffraction work of `,-Zn3(VO4)2' confirmed the C Bravais lattice, the space group was found to be Cm rather than C2/m, the difference perhaps arising from the inability of the X-rays to detect small displacements of oxygen. Attempts to refine the structure in Cm did not produce improved R factors. The relationship between the crystal structure of the L phase and the high-temperature C2/m,,-Zn2V2O7 thortveitite-type solid solution is discussed. [source] | |||||||||||||