Articles de revues : « X-ray crystal and powder diffraction »

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van Smaalen, Sander, Robert Dinnebier, Mikhail Sofin et Martin Jansen. « Structures of incommensurate and commensurate composite crystals Na x CuO2 (x = 1.58, 1.6, 1.62) ». Acta Crystallographica Section B Structural Science 63, n^o 1 (15 janvier 2007) : 17–25. http://dx.doi.org/10.1107/s0108768106039462.

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Na x CuO2 (x ≃ 1.6) has been synthesized for different compositions x, resulting in both commensurate and incommensurate composite crystals. The crystal structures are reported for two incommensurate compounds (x = 1.58 and 1.62) determined by Rietveld refinements against X-ray powder diffraction data. The incommensurate compounds and commensurate Na8Cu5O10 (x = 1.6) are found to possess similar structures, with valence fluctuations of Cu2+/Cu3+ as the origin of the modulations of the CuO2 subsystems; the displacive modulations of Na being defined by the closest Na—O contacts between the subsystems. A comparison of the structure models obtained from single-crystal X-ray diffraction, synchrotron-radiation X-ray powder diffraction and X-ray powder diffraction with Cu Kα1 radiation indicates that single-crystal X-ray diffraction is by far the most accurate method, while powder diffraction with radiation from an X-ray tube provides the least accurate structure model.

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Kimura, Fumiko, Wataru Oshima, Hiroko Matsumoto, Hidehiro Uekusa, Kazuaki Aburaya, Masataka Maeyama et Tsunehisa Kimura. « Magnetically Oriented Powder Crystal to Indexing and Structure Determination ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C1560. http://dx.doi.org/10.1107/s2053273314084393.

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In pharmaceutical sciences, the crystal structure is of primary importance because it influences drug efficacy. Due to difficulties of growing a large single crystal suitable for the single crystal X-ray diffraction analysis, powder diffraction method is widely used. In powder method, two-dimensional diffraction information is projected onto one dimension, which impairs the accuracy of the resulting crystal structure. To overcome this problem, we recently proposed a novel method of fabricating a magnetically oriented microcrystal array (MOMA), a composite in which microcrystals are aligned three-dimensionally in a polymer matrix. The X-ray diffraction of the MOMA is equivalent to that of the corresponding large single crystal, enabling the determination of the crystal lattice parameters and crystal structure of the embedded microcrytals.[1-3] Because we make use of the diamagnetic anisotropy of crystal, those crystals that exhibit small magnetic anisotropy do not take sufficient three-dimensional alignment. However, even for these crystals that only align uniaxially, the determination of the crystal lattice parameters can be easily made compared with the determination by powder diffraction pattern. Once these parameters are determined, crystal structure can be determined by X-ray powder diffraction method. In this paper, we demonstrate possibility of the MOMA method to assist the structure analysis through X-ray powder and single crystal diffraction methods. We applied the MOMA method to various microcrystalline powders including L-alanine, 1,3,5-triphenyl benzene, and cellobiose. The obtained MOMAs exhibited well-resolved diffraction spots, and we succeeded in determination of the crystal lattice parameters and crystal structure analysis.

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Laufek, Frantiek, Richard Paout et Emil Makovicky. « Crystal structure of owyheeite, Ag1.5Pb4.43Sb6.07S14 : refinement from powder synchrotron X-ray diffraction ». European Journal of Mineralogy 19, n^o 4 (13 septembre 2007) : 557–66. http://dx.doi.org/10.1127/0935-1221/2007/0019-1740.

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Paszkowicz, W., M. Marczak, A. M. Vorotynov, K. A. Sablina et G. A. Petrakovskii. « Powder diffraction study of LiCu2O2 crystals ». Powder Diffraction 16, n^o 1 (mars 2001) : 30–36. http://dx.doi.org/10.1154/1.1314389.

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LiCu2O2 crystals grown by spontaneous crystallization from the fluxed melt were studied by powder X-ray diffraction. The phase analysis shows that the applied growth conditions are suitable for preparation of a single-phase compound. The as-grown crystals contain only traces of foreign phases (Li2CuO2, CuO, Cu2O) typical for preparation of the LiCu2O2 compound. Attempts to anneal or quench the as-grown crystals led to two-phase samples containing LiCu2O2 and LiCu3O3. X-ray powder diffraction pattern of a LiCu2O2 crystal is reported and compared with literature data. The crystal structure is orthorhombic, space group Pnma, in agreement with literature data. Lattice parameters of the studied sample are a=5.7286(2) Å, b=2.8588(1) Å, and c=12.4143(3) Å. Time evolution of a diffraction pattern illustrates a slow increase of the secondary-phases contribution assumed to be due to interaction of the powdered crystal with humid air. A brief summary of compounds known in the Li–Cu–O system is included

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Mammadli, P. R., et D. M. Babanly. « POWDER X-RAY DIFFRACTION STUDY OF THE Cu3SbS3-CuI SYSTEM ». Chemical Problems 21, n^o 1 (2023) : 57–63. http://dx.doi.org/10.32737/2221-8688-2023-1-57-63.

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The nature of phase equilibria in the Cu3SbS3-CuI binary system over the entire concentration range were studied by means of the powder X-ray diffraction analysis (PXRD) for the first time at room temperature. It was found that the sample containing 66.7 mol.% CuI composed of a single phase and has a powder diffraction pattern completely different from the constituent phases of the system under study. The crystal lattice type and parameters, that were determined on the basis of the X-ray diffraction pattern of this sample using the TOPAS 4.2 and EVA computer programs are fully consistent with the literature data of the Cu5SbS3I2 four-component compound. The copper (I) iodide rich samples of the system consist of a two-phase mixture of Cu5SbS3I2 and CuI phases. However, the system is unstable in the Cu5SbS3I2-Cu3SbS3 composition range. In this concentration interval, the system is characterized by complex physico-chemical interaction of the initial components.

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Natarajan, Karthikeyan, Sathya Duraisamy et Sivakumar Kandasamy. « Ab initio and DFT study on Cu (II) complex salicylate derivative ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C1442. http://dx.doi.org/10.1107/s205327331408557x.

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X -ray diffraction becomes a routine process these decades for determining crystal structure of the materials. Most of the crystal structures solved nowadays is based on single crystal X-ray diffraction because it solves the crystal and molecular structures from small molecules to macro molecules without much human intervention. However it is difficult to grow single crystals of sufficient size and quality for conventional single-crystal X-ray diffraction studies. In such cases it becomes essential that structural information can be determined from powder diffraction data. With the recent developments in the direct-space approaches for structure solution, ab initio crystal structure analysis of molecular solids can be accomplished from X-ray powder diffraction data. It should be recalled that crystal structure determination from laboratory X-ray powder diffraction data is a far more difficult task than that of its single-crystal counterpart, particularly when the molecule possesses considerable flexibility or there are multiple molecules in the asymmetric unit. Salicylic acid and its derivatives used as an anti-inflammatory drug are known for its numerous medicinal applications. In our study, we synthesized mononuclear copper (II) complex of salicylate derivative. The structural characterization of the prepared compound was carried out using powder X-ray diffraction studies. Crystal structure of the compound has been solved by direct-space approach and refined by a combination of Rietveld method using TOPAS Academic V4.1. Density Functional Theory (DFT) calculations have to be carried in the solid state for the compound using GaussianW9.0 in the frame work of a generalized-gradient approximation (GGA). The geometry optimization was to be performed using B3LYP density functional theory. The atomic coordinates were taken from the final X-ray refinement cycle.

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Xu, Hongliang. « Structure determination from X-ray powder diffraction data at low resolution ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C143. http://dx.doi.org/10.1107/s2053273314098568.

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Knowledge of the structural arrangement of atoms in solids is necessary to facilitate the study of their properties. The best and most detailed structural information is obtained when the diffraction pattern of a single crystal a few tenths of a millimeter in each dimension is analyzed, but growing high-quality crystals of this size is often difficult, sometimes impossible. However, many crystallization experiments that do not yield single crystals do yield showers of randomly oriented micro-crystals that can be exposed to X-rays simultaneously to produce a powder diffraction pattern. Direct Methods routinely solve crystal structures when single-crystal diffraction data are available at atomic resolution (1.0-1.2Å), but fail to determine micro-crystal structures due to reflections overlapping and low-resolution powder diffraction data. By artificially and intelligently extending the measured data to atomic resolution, we have successfully solved structures having low-resolution diffraction data that were hard to solve by other direct-method based computation procedures. The newly developed method, Powder Shake-and-Bake, is implemented in a computer program PowSnB. PowSnB can be incorporated into the state-of-the-art software package EXPO that includes powder data reduction, structure determination and structure refinement. The new combination could have potential to solve structures that have never been solved before by direct-methods approach.

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Etschmann, Barbara, et Nobuo Ishizawa. « A synchrotron X-ray diffraction study of a small congruent LiNbO3 crystal : A compatible approach to powder diffraction ». Powder Diffraction 16, n^o 2 (juin 2001) : 81–85. http://dx.doi.org/10.1154/1.1365124.

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Single-crystal synchrotron X-ray diffraction (XRD) data were collected and refined for congruent lithium niobate crystals 8 and 6 μm in diameter, sizes that are comparable to the size of the powder particles used in powder diffraction. The motivation for using such small crystals is to minimize problems such as extinction, which decrease with crystal size. The R/wR factors were 0.011/0.014 and 0.019/0.018, for the 8 and 6 μm data, respectively, and the goodness of fit factors were 2.3(1) and 1.63(8), which compare favorably with values obtained from previous powder and single-crystal diffraction studies. Results from single-crystal XRD using crystals less than 10 μm in size may rival those obtained from powder diffraction.

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Murugesan, G., R. Nithya et S. Kalainathan. « Powder diffraction data on Ca0.9Nd0.1Ti0.9Al0.1O3 ». Powder Diffraction 30, n^o 3 (12 août 2015) : 294–95. http://dx.doi.org/10.1017/s0885715615000342.

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Single crystals of Ca0.9Nd0.1Ti0.9Al0.1O3 (CNTAO) were grown using optical floating zone technique and the grown crystals were characterized by Laue diffraction and powder X-ray diffraction techniques for crystal quality and its composition, respectively. The powder pattern of CNTAO was indexed and refined using GSAS program to an orthorhombic structure with space group Pbnm (#62), a = 5.3832(1), b = 5.4343(1), c = 7.6389(2) Å, V = 223.4677 Å3′, and Z = 4.

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Bandoli, G., M. Nicolini et A. Ongaro. « Powder Diffraction Data of Three Tetrahydropyridinyl Oxime Cognition Activators of Formula C8H15N2O+Cl− ». Powder Diffraction 7, n^o 3 (septembre 1992) : 170–73. http://dx.doi.org/10.1017/s088571560001856x.

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AbstractIndexed X-ray powder diffraction data are reported for three tetrahydropyridinyl oxime cognition activators. For these drugs of formula C8H15N2O+Cl− powder diffraction data calculated from single crystal structure determinations are also presented and compared to the experimentally observed powder diffraction data. Comparison of experimental and calculated powder patterns assures that single crystals are good representatives of the commercial powdered samples.

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Henaoa, J. A., J. M. Delgado et M. Quintero. « X-ray powder diffraction data for CuFeSe2 ». Powder Diffraction 9, n^o 2 (juin 1994) : 108–10. http://dx.doi.org/10.1017/s0885715600014068.

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Recent X-ray single-crystal diffraction studies have shown that CuFeSe2 crystallizes in the tetragonal system with space group P2c [, No. 112], Z = 4, with a =5.530(1) Å and c = 11.049(2) Å, c/a = 1.998. This material had been reported as pseudocubic with a =5.53 Å. The purpose of this paper is to present new X-ray powder diffraction data for CuFeSe2 and to compare the results with those reported for eskebornite, a mineral with ideal chemical composition CuFeSe2, and with those obtained from single-crystal structure data.

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Needham, F., J. Faber, T. G. Fawcett et D. H. Olson. « X-ray powder diffraction analysis of tegafur ». Powder Diffraction 21, n^o 3 (septembre 2006) : 245–47. http://dx.doi.org/10.1154/1.2210952.

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An experimental X-ray powder diffraction pattern was produced and analyzed for alpha-polymorphic tegafur, also called Ftorafur (an antineoplastic agent). The indexed data matched the powder patterns in the ICDD PDF-4/Organics database calculated from the reported single-crystal X-ray diffraction data in the Cambridge Structural Database. Alpha tegafur has a triclinic crystal system, with reduced cell parameters of a=16.720(6) Å, b=9.021(5) Å, c=5.995(3) Å, α=93.66(4)°, β=93.15(8)°, γ=100.14(4)°. There are four formula units contained in one unit cell. The cell volume and space group were determined to be 886.27 Å3 and P-1, respectively.

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Fitriani, Lili, Wahyu Alfath Firdaus, Wahyu Sidadang, Henni Rosaini, Okky Dwichandra Putra, Hironaga Oyama, Hidehiro Uekusa et Erizal Zaini. « Improved Solubility and Dissolution Rate of Ketoprofen by the Formation of Multicomponent Crystals with Tromethamine ». Crystals 12, n^o 2 (17 février 2022) : 275. http://dx.doi.org/10.3390/cryst12020275.

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This study aims to improve the dissolution rate of ketoprofen by preparing multicomponent crystals with tromethamine. The multicomponent crystals (equimolar ratio) of ketoprofen and tromethamine were prepared by the solvent co-evaporation method. The solid-state properties of the resulting powder were characterized by powder X-ray diffraction, DSC thermal analysis, FT–IR spectroscopy, solubility, and in vitro dissolution rate. The crystal structure of the multicomponent crystal was determined by single-crystal X-ray diffraction analysis. The results showed that the powder X-ray diffraction pattern of the ketoprofen–tromethamine binary system was different from that of the starting materials. This difference indicates the formation of a new crystalline phase between ketoprofen and tromethamine (equimolar ratio). The DSC thermogram of the ketoprofen–tromethamine binary system exhibited a single and sharp endothermic peak at 128.67 °C, attributed to the melting point of a multicomponent crystal of ketoprofen–tromethamine. A single-crystal X-ray analysis revealed that ketoprofen–tromethamine formed a layered structure, salt-type multicomponent crystal. The solubility and dissolution rate of the multicomponent crystal were notably enhanced compared to the intact ketoprofen. The ketoprofen–tromethamine binary system forms salt-type multicomponent crystals, which can significantly increase the solubility and dissolution rate.

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Cox, D. E. « Synchrotron X-Ray Powder Diffraction ». MRS Bulletin 12, n^o 1 (février 1987) : 16–20. http://dx.doi.org/10.1557/s088376940006869x.

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X-ray powder diffraction is one of the most widely used techniques by scientists engaged in the synthesis, analysis, and characterization of solids. It is estimated that there are now about 25,000 users throughout the world, of which about one third are in the United States. Any single-phase polycrystalline material gives an x-ray pattern which can be regarded as a unique “fingerprint,” and modern automated search-and-match techniques used in conjunction with the Powder Diffraction File (maintained by the International Center for Diffraction Data, Swarthmore, PA) allow routine analysis of samples in minutes. From an x-ray pattern of good quality it is possible to determine unit cell parameters with high accuracy and impurity concentrations of 1-5%, so that powder techniques are extremely valuable in phase equilibrium studies and residual stress measurements, for example. In addition, a detailed analysis of line shapes gives information about physical properties such as the size and shape of the individual crystallites, microscopic strain, and stacking disorder.In the early days of crystallography many simple (and some not-so-simple) structures were solved from x-ray powder diffraction patterns, but the obvious limitations to the number of individual reflection intensities which can be estimated and the increasing sophistication of single-crystal techniques resulted in a decline in the importance of this application in the 1950s and 1960s.

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Rawn, C. J., R. S. Roth et H. F. McMurdie. « Powder X-Ray Diffraction Data for Ca2Bi2O5and C4Bi6O13 ». Powder Diffraction 7, n^o 2 (juin 1992) : 109–11. http://dx.doi.org/10.1017/s0885715600018352.

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AbstractSingle crystals and powder samples of Ca2Bi5O5and Ca4Bi6O13have been synthesized and studied using single crystal X-ray diffraction as well as X-ray and neutron powder diffraction. Unit cell dimensions were calculated using a least squares analysis that refined to a δ2θof no more than 0.03°. A triclinic cell was found with space group , a = 10.1222(7), b = 10.1466(6), c = 10.4833(7) Å. α= 116.912(5), β= 107.135(6) and γ= 92.939(6)°, Z = 6 for the Ca2Bi2O5compound. An orthorhombic cell was found with space group C2mm, a = 17.3795(5), b = 5.9419(2) and c = 7.2306(2) Å, Z = 2 for the Ca4Bi6O13compound.

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Gonzalez, Diana, Joseph T. Golab, James A. Kaduk, Amy M. Gindhart et Thomas N. Blanton. « Powder X-ray diffraction of fluorometholone, C22H29FO4 ». Powder Diffraction 35, n^o 1 (mars 2020) : 71–72. http://dx.doi.org/10.1017/s0885715619000915.

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Commercial fluorometholone, CAS #426-13-1, crystallizes in the monoclinic space group P21 (#4) with a = 6.40648(2), b = 13.43260(5), c = 11.00060(8) Å, β = 92.8203(5)°, V = 945.517(5) Å3, and Z = 2. A reduced cell search in the Cambridge Structural Database yielded one previous structure determination, using single-crystal data at 292 K. In this work, the sample was ordered from the United States Pharmacopeial Convention (Lot # R032K0) and analyzed as-received. The room temperature (295 K) crystal structure was refined using synchrotron (λ = 0.412826 Å) powder diffraction data and optimized using density functional theory (DFT) techniques. Hydrogen positions were included as a part of the structure and were re-calculated during the refinement. The diffraction data were collected on beamline 11-BM at the Advanced Photon Source, Argonne National Laboratory, and the powder X-ray diffraction pattern of the compound has been submitted to ICDD® for inclusion in the Powder Diffraction File™. The agreement of the Rietveld-refined and DFT-optimized structures is excellent; the root-mean-square Cartesian displacement is 0.060 Å. In addition to the O–H⋯O hydrogen bonds observed by Park et al. (Park, Y. J., Lee, M. Y., and Cho, S. I. (1992). “Fluorometholone,” J. Korean Chem. Soc. 36, 812–817), C–H⋯O hydrogen bonds contribute to the crystal energy.

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Pan, QingQing, Ping Guo, Jiong Duan, Qiang Cheng et Hui Li. « Comparative crystal structure determination of griseofulvin : Powder X-ray diffraction versus single-crystal X-ray diffraction ». Chinese Science Bulletin 57, n^o 30 (28 juin 2012) : 3867–71. http://dx.doi.org/10.1007/s11434-012-5245-5.

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Wims, A. M., et C. D. Fuerst. « X-ray powder data for Nd2Co14B, Pr2Co14B and Pr2Fe14B ». Powder Diffraction 9, n^o 3 (septembre 1994) : 189–93. http://dx.doi.org/10.1017/s0885715600019205.

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The crystal structure data have been determined by X-ray diffraction for three rare earth magnetic materials, Nd2Co14B, Pr2Co14B, and Pr2Fe14B. The data were evaluated with several computer programs desingned for that purpose. The crystal structure for Nd2Co14B and Pr2Fe14D determined by X-ray diffraction agree with those obtained earlier by neutron diffraction.

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Garin, Jorge L., et Rodolfo L. Mannheim. « X-ray powder diffraction pattern of Mo4.8Si3C0.6 ». Powder Diffraction 8, n^o 1 (mars 1993) : 65–67. http://dx.doi.org/10.1017/s0885715600017784.

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The title compound was synthesized by high temperature reaction of the component elements. This phase, formerly classified in the group of Nowotny phases, crystallizes in the hexagonal system with space group P63/mcm. Crystal data and indexed X-ray powder diffraction data are reported.

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Kolb, Ute, Yasar Krysiak, Tatiana Gorelik et Enrico Mugnaioli. « Electron and X-ray diffraction – two worlds united ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C926. http://dx.doi.org/10.1107/s2053273314090731.

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Small crystals structure solution usually done with X-ray powder diffraction (XRPD) provides bulk information and is powerful for in-situ investigations. Peak overlap in the one-dimensional data causes problems e.g. for polyphasic or impure samples and large cell parameters thus peak indexing and intensity extraction are the main issues where x-ray powder data may be supported by extra information. Electrons sample smaller volumes but strong coulombic interaction cause multiple scattering effects changing intensities often so strong that a structure solution is becoming impossible. Nevertheless, oriented electron diffraction patterns may provide sufficient information to support indexing or the assignment of impurity peaks in the case of low quality x-ray powder pattern. Reciprocal space tomography [1] uses a series of non-oriented diffraction patterns for which dynamical effects are significantly reduced and an enhanced amount of independent reflections sampled allows "ab-initio" crystal structure solution using established X-ray structure solution packages. Although structure refinement based on kinematical intensities is stable, achievable R values of 10-30% are high and final refinement may be performed based on X-ray powder data. Scanning transmission electron microscopy (STEM) for crystal tracking and nano electron diffraction (NED) is suitable for beam sensitive material, agglomerated particles, twins or intergrown phases on crystals down to 30nm size [2, 3]. Interesting properties of nanocrystalline materials are driven mainly by twinning, defects, disorder in one or two dimensions down to the amorphous state. Here low data completeness or uncertain intensity determination causes problems in structure solution. Here a mean structure may be determinable serving as a basis for disorder description and being used as a starting model being refined onto X-ray powder data maybe supported by a combination of the diffraction methods or by adding extra information.

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Nørlund Christensen, A., MS Lehmann et M. Nielsen. « Solving Crystal Structures from Powder Diffraction Data ». Australian Journal of Physics 38, n^o 3 (1985) : 497. http://dx.doi.org/10.1071/ph850497.

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High resolution powder data from both neutron and X-ray (synchrotron) sources have been used to estimate the possibility of direct structure determination from powder data. Two known structures were resolved by direct methods with neutron and X-ray data. With synchrotron X-ray data, the measured range of data was insufficient for a structure analysis, but the R-factor calculations showed the intensities extracted from the profile data to be of acceptable quality. The results were used to estimate the largest structure that might be solved using routine techniques. It was found that the limit would be near twenty atoms in the asymmetric part of a centro-symmetric structure.

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Garsche, Markus, Ekkehart Tillmanns, Thomas Bauer, Reinhard X. Fischer et Ladislav Bohaty. « Powder Diffraction Data of Some Acentric Tartrates and Tartrato-Antimonates ». Powder Diffraction 6, n^o 2 (juin 1991) : 107–10. http://dx.doi.org/10.1017/s0885715600017115.

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AbstractSix acentric tartrates and tartrato-antimonates have been investigated by means of X-ray powder diffraction. Single crystals were obtained by evaporation from aqueous solutions. The compounds have attracted attention because of their electrostrictive and electro-optical effects. Complete crystal data for the six compounds are reported. X-ray powder diffraction patterns for Rb2C4H4O6 and Ca [Sb2{C4H2O6}2]·2H2O are given.

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Sreenivasan, R. S., N. Kanagathara, G. Ezhamani, N. G. Renganathan et G. Anbalagan. « Effect of Metal Dopant on Ninhydrin—Organic Nonlinear Optical Single Crystals ». Journal of Spectroscopy 2013 (2013) : 1–5. http://dx.doi.org/10.1155/2013/386024.

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In the present work, metal (Cu2+)-substituted ninhydrin single crystals were grown by slow evaporation method. The grown crystals have been subjected to single crystal XRD, powder X-ray diffraction, FTIR, dielectric and SHG studies. Single crystal X-ray diffraction analysis reveals that the compound crystallizes in monoclinic system with noncentrosymmetric space group P21 with lattice parametersa=11.28 Å,b=5.98 Å,c=5.71 Å,α=90∘,β=98.57,γ=90∘, andV=381 (Å)3, which agrees very well with the reported value. The sharp and strong peaks in the powder X-ray diffraction pattern confirm the good crystallinity of the grown crystals. The presence of dopants marginally altered the lattice parameters without affecting the basic structure of the crystal. The UV-Vis transmittance spectrum shows that the crystal has a good optical transmittance in the entire visible region with lower cutoff wavelength 314 nm. The vibrational frequencies of various functional groups in the crystals have been derived from FT-IR analysis. Based on the shifts in the vibrations, the presence of copper in the lattice of the grown crystal is clearly established from the pure ninhydrin crystals. Both dielectric constant and dielectric loss decrease with the increase in frequency. The second harmonic generation efficiency was measured by employing powder Kurtz method.

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Manimekalai, R., et S. Chidambaram. « Growth and Characterization of Adipic Acid Doped Potassium Hydrogen Phthalate : A Nonlinear Optical Single Crystal ». Asian Journal of Chemistry 32, n^o 1 (18 novembre 2019) : 79–83. http://dx.doi.org/10.14233/ajchem.2020.22273.

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Adipic acid doped potassium hydrogen phthalate (AAKHP) and pure potassium hydrogen phthalate single crystals were grown by slow evaporation method. Single crystal X-ray diffraction analysis was carried out to determine the lattice parameters in a = 6.47 Å, b = 9.59 Å, c = 13.25 Å and space group of Pca21. This confirms the grown AAKHP belongs to the orthorhombic system. Various diffracting planes of the grown crystal were indexed using powder X-ray diffraction study. Fourier-transform infrared studies confirm the presence of various functional groups in the grown crystal. The transmittance spectrum shows that the lower cutoff wavelength is around 290 nm. The nonlinear optical property of the grown crystal has been studied by Kurtz powder second harmonic generation (SHG) analysis. EDAX analysis confirms the presence of various elements in the AAKHP crystal. Vickers micro-hardness studies are used for the analysis of mechanical behaviour of the grown crystal. The paramagnetic nature of the grown crystal was confirmed by vibration spectrum magnetometer technique.

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Wark, J. S., et H. He. « Subpicosecond X-ray diffraction ». Laser and Particle Beams 12, n^o 3 (septembre 1994) : 507–13. http://dx.doi.org/10.1017/s0263034600008363.

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With the advent of ultrashort (subpicosecond) high-power lasers it is now possible to create intense bursts of X-rays with subpicosecond durations. An analysis of the temporal response of diffraction of such X-rays by crystals in both the dynamical and kinematic regime is presented. It is also shown that under certain conditions the temporal resolution can be determined by the response of the crystal.

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Patel, Nilan V., Joseph T. Golab, James A. Kaduk, Amy M. Gindhart et Thomas N. Blanton. « Powder X-ray diffraction of flucytosine, C4H4FN3O ». Powder Diffraction 35, n^o 1 (7 janvier 2020) : 67–68. http://dx.doi.org/10.1017/s0885715619000903.

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Flucytosine, CAS #2022-85-7, crystallizes in the tetragonal space group P41212 (#94) with a = 6.643768(27), c = 23.89009(10) Å, V = 1054.500(7) Å3, and Z = 8. In this work, the sample was obtained from the United States Pharmacopeial Convention (USP) Lot #R03100 and analyzed as-received. The room temperature (295 K) crystal structure was refined using synchrotron (λ = 0.412826 Å) powder diffraction data and optimized using the density functional theory (DFT). When looking down the a-axis, the crystal structure consists of multiple ribbon-like structures stacked into columns. The powder X-ray diffraction pattern of the compound has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®). The agreement of the Rietveld-refined and DFT-optimized structures is good, with the largest difference in the external amine group with an overall root mean displacement of 0.056 Å. There is also evidence of unit cell expansion at higher temperatures, as the volume of the unit cell at 298 K was 1.6–1.9% greater than the two unit cells obtained at 150 K. A N–H⋯O hydrogen bond exists in the inter-ribbon region between the flucytosine molecules, resulting in a 3D hydrogen bond network.

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Frankær, Christian, Majbritt Thymark, Kenny Ståhl, Olga Moroz, Keith Wilson et Pernille Harris. « X-ray powder diffraction : A powerful tool for industrial protein production ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C1559. http://dx.doi.org/10.1107/s205327331408440x.

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X-ray powder diffraction (XRPD) offers a method of characterizing a crystalline protein suspension [1], and data can be collected within 30 minutes, which is appealing for industrial applications. In industry, enzymes are produced and handled in high concentrations, which can in turn cause problems for the processes due to protein precipitation in the production pipeline. XRPD is useful for identification of the crystal forms present, by fitting calculated patterns of known single crystal forms to the observed XRPD pattern. For this purpose we have developed a streamlined program for calculation of diffraction patterns from pdb-files taking into account bulk-solvent, peak asymmetry and background [2]. XRPD was applied to a suspension from a large-scale industrial production of the widely used Bacillus lentus subtilisin. A dominant crystal form was identified by XRPD, but two other different crystal forms were found by a complementary single crystal micro-diffraction analysis of the larger single crystals present in the sample [3]. The study serves as a reminder that when a crystal is picked out from a batch crystallization for single crystal analysis, it might not be representative of the bulk microcrystalline material in the sample. To estimate the fraction of the different crystal forms in production samples with significant polymorphism, a further XRPD study was performed on binary mixtures of different lysozyme and subtilisin crystal forms. Quantitative XRPD generally requires careful sample preparation, and working with protein slurries leads to further challenges in terms of varying crystal density. After careful optimisation of suspension medium, the relative composition of crystal forms can be determined within 10%. This work demonstrates the value of in-house XRPD as an analysis tool in industrial enzyme production, and its potential to help troubleshooting the production process and to provide information for further refining the manufacturing of enzymes.

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Jarabek, B. R., D. G. Grier et G. J. McCarthy. « X-ray powder diffraction data for BaPbO3 ». Powder Diffraction 11, n^o 1 (mars 1996) : 56–59. http://dx.doi.org/10.1017/s0885715600008939.

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Crystal and X-ray powder diffraction data are presented for BaPbO3. The powder pattern was indexed and refined on an orthorhombic cell with a=6.0264(3)Å , b=8.5078(3)Å , c=6.0629(2)Å, Z=4, space group Imma. The phase may actually be monoclinic with space group I2/m, but no distortion from the orthorhombic cell was evident in the powder patterns, suggesting a β angle very close to 90.0°.

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Gorelik, Tatiana E., Jacco van de Streek, Herbert Meier, Lars Andernach et Till Opatz. « Crystal structure analysis of a star-shaped triazine compound : a combination of single-crystal three-dimensional electron diffraction and powder X-ray diffraction ». Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 74, n^o 3 (18 mai 2018) : 287–94. http://dx.doi.org/10.1107/s2052520618006686.

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The solid-state structure of star-shaped 2,4,6-tris{(E)-2-[4-(dimethylamino)-phenyl]ethenyl}-1,3,5-triazine is determined from a powder sample by exploiting the respective strengths of single-crystal three-dimensional electron diffraction and powder X-ray diffraction data. The unit-cell parameters were determined from single crystal electron diffraction data. Using this information, the powder X-ray diffraction data were indexed, and the crystal structure was determined from the powder diffraction profile. The compound crystallizes in a noncentrosymmetric space group,P212121. The molecular conformation in the crystal structure was used to calculate the molecular dipole moment of 3.22 Debye, which enables the material to show nonlinear optical effects.

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Zeng, Lingmin, Lianqin Nong, Junqin Li, Yinghong Zhuang et Jianmin Hao. « Crystal and X-ray powder data for ErNiSb ». Powder Diffraction 11, n^o 1 (mars 1996) : 40–41. http://dx.doi.org/10.1017/s0885715600008897.

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Indexed powder diffraction patterns and related crystallographic data are reported for ErNiSb, which is not represented in the X-ray Powder Diffraction File. The compound ErNiSb is cubic [space group F43m, Z=4, a=6.2693(1) Å]. The R=0.067 indicates that experimental intensities agree well with the calculated patterns.

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Needham, F., C. E. Crowder, J. W. Reid, T. G. Fawcett et J. Faber. « X-ray powder diffraction analysis of imipenem monohydrate ». Powder Diffraction 27, n^o 1 (mars 2012) : 20–24. http://dx.doi.org/10.1017/s0885715612000048.

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An experimental X-ray powder diffraction pattern was produced and analyzed for imipenem monohydrate, an antimicrobial pharmaceutical agent. Although there are no experimental powder patterns in the ICDD PDF-4/Organics Database, there is one powder pattern calculated with single-crystal X-ray diffraction data from the Cambridge Structural Database. Here, we report the refined experimental powder diffraction data for imipenem monohydrate. These data for imipenem monohydrate are consistent with an orthorhombic crystal system having reduced unit-cell parameters of a = 8.2534(3) Å, b = 11.1293(4) Å, and c = 15.4609(6) Å. The resulting unit-cell volume, 1420.15(15) Å3, indicates four formula units per unit cell. Observed peaks are consistent with the P212121 space group.

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Bandoli, G., M. Nicolini et A. Ongaro. « Powder Diffraction Data of Three 9-Amino-1,2,3,4- Tetrahydroacridine Alzheimer's Disease Therapeutics ». Powder Diffraction 6, n^o 4 (décembre 1991) : 196–99. http://dx.doi.org/10.1017/s0885715600017516.

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AbstractTacrine hydrochloride monohydrate, velnacrine maleate and suronacrine maleate have been investigated by means of X-ray powder diffraction. The unit cell dimensions, determined by single-crystal diffraction data, agree well with those of powder diffraction analysis, which is characterized by good figures of merit for the three drugs. Present work assures that single-crystals are good representatives of the commercial powdered samples, since experimental and simulated (from structure determination) powder patterns are practically identical.

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Liang, Zhen-Hua, Kai-Bin Tang, Qian-Wang Chen et Hua-Gui Zheng. « RbCa2Nb3O10from X-ray powder data ». Acta Crystallographica Section E Structure Reports Online 65, n^o 6 (23 mai 2009) : i44. http://dx.doi.org/10.1107/s1600536809018157.

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Rubidium dicalcium triniobate(V), RbCa2Nb3O10, has been synthesized by solid-state reaction and its crystal structure refined from X-ray powder diffraction data using Rietveld analysis. The compound is a three-layer perovskite Dion–Jacobson phase with the perovskite-like slabs derived by termination of the three-dimensional CaNbO3perovskite structure along theabplane. The rubidium ions (4/mmmsymmetry) are located in the interstitial space.

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Punitha, P., et S. Senthilkumar. « CRYSTAL DEVELOPMENT, THERMAL AND CRYSTALLINE PERFECTION OF POTASSIUM MAGNESIUM COBALT SULFATE HEXAHYDRATE MIXED CRYSTALS ». Rasayan Journal of Chemistry 14, n^o 04 (2021) : 2810–19. http://dx.doi.org/10.31788/rjc.2021.1446571.

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Potassium magnesium cobalt sulfate hexahydrate (KMCS) was synthesized and single crystals were obtained with a slow evaporation solution growth technique (SESGT). KMCS empirical formula is K2Mg0.26Co0.74(SO4)26H2O with the weight of equation 428.34. KMCS crystal exposed monoclinic space groupP21/c, a = 6.1457, b = 12.2208, c = 9.0677, a = g = 90 °, b = 105 °, V = 657.87, Z = 2, 2.162 Mg m-3, in pink colour.The rate of frequency reduction found in powder indicates the crystal stress resulting from the processing of grown crystals. Single crystals are performed with FT-IR and UV-vis spectral studies. High-resolution X-ray diffraction (HRXRD) indicates prevalent site occupation substitution Co (II). For powder X-ray diffraction (XRD) results in the development of crystal stress due to the formation of single crystals. Electron microscopy scanning (SEM) tests the morphological changes in the exterior. The introduction of dopant into the crystalline medium has been verified by energy-dispersive X-ray spectroscopy (EDS). TG-DTA research has been conducted for single crystal thermal studies.

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Fewster, Paul F. « A new theory for X-ray diffraction ». Acta Crystallographica Section A Foundations and Advances 70, n^o 3 (27 mars 2014) : 257–82. http://dx.doi.org/10.1107/s205327331400117x.

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This article proposes a new theory of X-ray scattering that has particular relevance to powder diffraction. The underlying concept of this theory is that the scattering from a crystal or crystallite is distributed throughout space: this leads to the effect that enhanced scatter can be observed at the `Bragg position' even if the `Bragg condition' is not satisfied. The scatter from a single crystal or crystallite, in any fixed orientation, has the fascinating property of contributing simultaneously to many `Bragg positions'. It also explains why diffraction peaks are obtained from samples with very few crystallites, which cannot be explained with the conventional theory. The intensity ratios for an Si powder sample are predicted with greater accuracy and the temperature factors are more realistic. Another consequence is that this new theory predicts a reliability in the intensity measurements which agrees much more closely with experimental observations compared to conventional theory that is based on `Bragg-type' scatter. The role of dynamical effects (extinctionetc.) is discussed and how they are suppressed with diffuse scattering. An alternative explanation for the Lorentz factor is presented that is more general and based on the capture volume in diffraction space. This theory, when applied to the scattering from powders, will evaluate the full scattering profile, including peak widths and the `background'. The theory should provide an increased understanding of the reliability of powder diffraction measurements, and may also have wider implications for the analysis of powder diffraction data, by increasing the accuracy of intensities predicted from structural models.

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Lindsay, C. G., C. J. Rawn et R. S. Roth. « Powder X-ray diffraction data for Ba4ZnTi11O27 and Ba2ZnTi5O13 ». Powder Diffraction 9, n^o 1 (mars 1994) : 56–62. http://dx.doi.org/10.1017/s0885715600019709.

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Single crystals and powder samples of Ba4ZnTi11O27 and Ba2ZnTi5O13 have been synthesized and studied using single-crystal X-ray precession photographs and X-ray powder diffraction. Unit cell dimensions were calculated from a least-squares refinement with a final maximum Δ2θ of 0.05°. Both phases were found to have monoclinic cells, space group C2/m. The refined lattice parameters for the Ba4ZnTi11O27 compound are a= 19.8687(8) Å, b=11.4674(5) Å, c=9.9184(4) Å, β= 109.223(4)°, and Z=4. The refined lattice parameters for the Ba2ZnTi5O13 compound are a= 15.2822(7) Å, b=3.8977(1) Å, c=9.1398(3) Å, β=98.769(4)°, and Z=2.

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Kloda, Matouš, Irena Matulková, Ivana Císařová, Petra Becker, Ladislav Bohatý, Petr Němec, Róbert Gyepes et Ivan Němec. « Cocrystals of 2-Aminopyrimidine with Boric Acid—Crystal Engineering of a Novel Nonlinear Optically (NLO) Active Crystal ». Crystals 9, n^o 8 (3 août 2019) : 403. http://dx.doi.org/10.3390/cryst9080403.

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Crystal engineering of novel materials for nonlinear optics (NLO) based on 2-aminopyrimidine yielded two molecular cocrystals with boric acid—trigonal (P3221 space group) 2-aminopyrimidine—boric acid (3/2) and monoclinic (C2/c space group) 2-aminopyrimidine—boric acid (1/2). In addition to crystal structure determination by single crystal X-ray diffraction, the cocrystals were characterized by powder X-ray diffraction and vibrational spectroscopy (FTIR and FT Raman). Large single crystals of the non-centrosymmetric cocrystal 2-aminopyrimidine—boric acid (3/2) were grown to study the optical properties and determine the second harmonic generation (SHG) efficiency (using 800 nm fundamental laser line) of powder samples.

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Ivashkevich, Ludmila S., Kirill A. Selevich, Anatoly I. Lesnikovich et Anatoly F. Selevich. « X-ray powder diffraction study of LiCrP2O7 ». Acta Crystallographica Section E Structure Reports Online 63, n^o 3 (14 février 2007) : i70—i72. http://dx.doi.org/10.1107/s1600536807005752.

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The monoclinic crystal structure of lithium chromium(III) diphosphate, LiCrP2O7, isotypic with other members of the series LiM IIIP2O7 (M III = Mn, Fe, V, Mo, Sc and In), was refined from laboratory X-ray powder diffraction data using the Rietveld method. The Cr3+ cation is bonded to six O atoms from five diphosphate anions to form a distorted octahedron. Links between the bent diphosphate anions and the Cr3+ cations result in a three-dimensional network, with tunnels filled by the Li+ cations in a considerably distorted tetrahedral environment of O atoms.

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Boullay, Philippe, Gwladys Mouillard, Nicolas Barrier, Olivier Perez et Lukas Palatinus. « Electron Diffraction vs aperiodic crystal : from indexation to structure solution ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C1194. http://dx.doi.org/10.1107/s2053273314088056.

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Can we solve aperiodic structures using intensities from electron diffraction? Yes! How? No mystery about it: the data analysis and the tools used for structure solution are essentially the same as the ones used in X-ray crystallography. The trick actually lies in new approaches used in electron crystallography. In analogy to X-ray diffraction, the so-called Electron Diffraction Tomography (EDT) [1] corresponds to a phi-scan data collection on a single crystal. There lies one major advantage of this technique: a powder sample is easily converted to infinitely large number of single crystals for electron diffraction. In case of aperiodic crystals this makes the difference over X-ray or neutron powder diffraction where, often, the lack of peaks clearly assignable to satellite reflections prevents any indexation and further analysis of the structure [2]. EDT allows for an accurate estimation of the modulation vector and a good guess of the super space group. These informations can be advantageously used as an input for X-ray or neutron powder diffraction. Not limited to indexation, EDT combined with Precession Electron Diffraction (PED) [3], offers a unique tool for solving modulated structures when crystals suitable for X-ray diffraction are missing. By limiting the paths for multiple scattering, PED makes the diffracted intensities closer to kinematical approximation so that they can be used efficiently for structure solution. Regarding aperiodic crystals, the superspace electron density map, generated as an output of the charge flipping algorithm used in Superflip, can be interpreted to obtain a structural model. This will be illustrated on a series of layered materials closely related to the Aurivillius phases belonging to the pseudo-binary Bi5Nb3O15-ABi2Nb2O9 (A=Pb, Sr, Ca, Ba). Limitations and possible combination with powder diffraction patterns will be discussed.

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D. S., Christy, Sahaya Shajan X. et Mahadevan C. K. « Study of Physico-Chemical Properties and Growth Dimension Augmentation of Barium Succinate Single Crystals Grown by Slow Evaporation Technique ». Journal of Physical Science 33, n^o 1 (25 avril 2022) : 29–49. http://dx.doi.org/10.21315/jps2022.33.1.3.

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Slow evaporation method was adopted to grow barium succinate (BS) single crystals for the first time and diamond shape crystals were successfully synthesised with dimension 14 mm3 × 17 mm3 × 4 mm3. Single crystal x-ray diffraction studies show that the crystal system is monoclinic. Powder x-ray diffraction studies confirmed the crystallinity of the grown BS crystal. From energy dispersive x-ray spectroscopy (EDS) analysis the presence of barium metal was confirmed. The functional group of the BS crystal was confirmed from fourier transform infrared (FTIR) spectrum. The crystals were found to be hydrated and thermally stable up to 150°C. BS crystal possesses good transmittance in the wavelength range 250 nm–1200 nm and it is non-linear optical (NLO) active material. The BS crystals have mechanical softness and normal dielectric behaviour.

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Kaduk, James A., Amy M. Gindhart et Thomas N. Blanton. « Powder X-ray diffraction of capecitabine, C15H22FN3O6 ». Powder Diffraction 34, n^o 3 (11 juillet 2019) : 282–83. http://dx.doi.org/10.1017/s0885715619000575.

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Capecitabine (Xeloda) is a chemotherapy drug used to treat breast, gastric, and colorectal cancers. Commercial capecitabine crystallizes in the orthorhombic space group P212121 (#19) with a = 5.20587(3), b = 9.52324(4), c = 34.79574(21) Å, V = 1725.062(12) Å3, and Z = 4. A reduced cell search in the Cambridge Structural Database (Groom C. R., Bruno, I. J., Lightfoot, M. P., and Ward, S. C. (2016) Crystallogr. Sect. B: Struct. Sci., Cryst. Eng. Mater.72, 171–179) yielded three previous structure determinations (Rohlicek, J., Husak, M., Gavenda, A., Jegorov, A., Kratochvil, B., and Fitch, A. (2016). Acta Cryst. Sect. E: Crystallgr. Commun.72, 879–880, BOVDUM; Malińska, M., Krzeczyński, P., Czerniec-Michalik, E., Trzcińska, K., Cmoch, P., Kutner, A., and Woźniak, K. (2014). J. Pharm. Sci.103, 587–593, BOVDUM01 and BOVDUM02), using synchrotron powder data and later single crystal data at two temperatures. In this work, the sample was ordered from United States Pharmacopeial Convention (lot # G0J205), and analyzed as-received. The room temperature (295 K) crystal structure was refined using synchrotron (λ = 0.413914 Å) powder diffraction data, density functional theory (DFT), and Rietveld refinement techniques. Hydrogen positions were included as part of the structure, and were re-calculated during the refinement. The diffraction data were collected on a beamline 11-BM at the Advanced Photon Source, Argonne National Laboratory and the powder X-ray diffraction pattern of the compound is provided. The agreement of the Rietveld-refined and DFT-optimized structures is poorest in the pentyl side chain, consistent with the disorder observed previously.

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Ermrich, M., F. Hahn et E. R. Wölfel. « Use of Imaging Plates in X-Ray Analysis ». Textures and Microstructures 29, n^o 1-2 (1 janvier 1997) : 89–101. http://dx.doi.org/10.1155/tsm.29.89.

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Two-dimensional detectors have opened a new area for the investigation of both single crystals and polycrystalline materials. The working principle of Imaging Plates is described. Some characteristics and the advantages of an Imaging Plate are discussed using the STOE Imaging Plate Diffraction System for different kinds of X-ray analysis: (i) single crystal diffractometry, (ii) powder diffraction and (iii) stress and texture investigations.

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Muangsin, Nongnuj, Malee Prajuabsook, Pitiporn Chimsook, Nuanphun Chantarasiri, Krisana Siraleartmukul, Narongsak Chaichit et Supot Hannongbua. « Structure determination of diclofenac in a diclofenac-containing chitosan matrix using conventional X-ray powder diffraction data ». Journal of Applied Crystallography 37, n^o 2 (17 mars 2004) : 288–94. http://dx.doi.org/10.1107/s0021889804002353.

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The structure determination of diclofenac embedded in a diclofenac-containing chitosan matrix using conventional X-ray powder diffraction data is demonstrated. It reveals that sodium diclofenac, the starting material in the preparation of a controlled-release diclofenac-containing chitosan matrix, changes to diclofenac acid in space groupC2/cin the matrix. Simple methods were employed for handling the sample to obtain X-ray powder diffraction data of sufficiently high quality for the determination of the crystal structure of diclofenac embedded in chitosan. These involved grinding and sieving several times through a micro-mesh sieve to obtain a suitable particle size and a uniformly spherical particle shape. A traditional technique for structure solution from X-ray powder diffraction data was applied. The X-ray diffraction intensities were extracted using Le Bail's method. The structure was solved by direct methods from the extracted powder data and refined using the Rietveld method. For comparison, the single-crystal structure of the same drug was also determined. The result shows that the crystal structure solved from conventional X-ray powder diffraction data is in good agreement with that of the single crystal. The deviations of the differences in bond lengths and angles are of the order of 0.030 Å and 0.639°, respectively.

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Bolla, Geetha, Vladimir Chernyshev et Ashwini Nangia. « Acemetacin cocrystal structures by powder X-ray diffraction ». IUCrJ 4, n^o 3 (8 mars 2017) : 206–14. http://dx.doi.org/10.1107/s2052252517002305.

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Cocrystals of acemetacin drug (ACM) with nicotinamide (NAM),p-aminobenzoic acid (PABA), valerolactam (VLM) and 2-pyridone (2HP) were prepared by melt crystallization and their X-ray crystal structures determined by high-resolution powder X-ray diffraction. The powerful technique of structure determination from powder data (SDPD) provided details of molecular packing and hydrogen bonding in pharmaceutical cocrystals of acemetacin. ACM–NAM occurs in anhydrate and hydrate forms, whereas the other structures crystallized in a single crystalline form. The carboxylic acid group of ACM forms theacid–amide dimer three-point synthonR32(9)R22(8)R32(9) with three differentsynamides (VLM, 2HP and caprolactam). The conformations of the ACM molecule observed in the crystal structures differ mainly in the mutual orientation of chlorobenzene fragment and the neighboring methyl group, beinganti(type I) orsyn(type II). ACM hydrate, ACM—NAM, ACM–NAM-hydrate and the piperazine salt of ACM exhibit the type I conformation, whereas ACM polymorphs and other cocrystals adopt the ACM type II conformation. Hydrogen-bond interactions in all the crystal structures were quantified by calculating their molecular electrostatic potential (MEP) surfaces. Hirshfeld surface analysis of the cocrystal surfaces shows that about 50% of the contribution is due to a combination of strong and weak O...H, N...H, Cl...H and C...H interactions. The physicochemical properties of these cocrystals are under study.

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Ibiapino, Amanda Laura, Rafael Cardoso Seiceira, Altivo Pitaluga, Antonio Carlos Trindade et Fabio Furlan Ferreira. « Structural characterization of form I of anhydrous rifampicin ». CrystEngComm 16, n^o 36 (2014) : 8555–62. http://dx.doi.org/10.1039/c4ce01157k.

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Kimura, Fumiko, Tsunehisa Kimura, Wataru Oshima, Masataka Maeyama et Kazuaki Aburaya. « X-ray diffraction study of a pseudo single crystal prepared from a crystal belonging to point group 2 ». Journal of Applied Crystallography 43, n^o 1 (18 décembre 2009) : 151–53. http://dx.doi.org/10.1107/s0021889809048006.

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A pseudo single crystal (a composite of matrix resin and powder crystallites, wherein the individual crystallites are aligned three-dimensionally) was prepared from a powder of sucrose, and its X-ray diffraction pattern was studied. A powder of sucrose crystals suspended in a UV-curable resin precursor was subjected to magnetic alignment in order to align the individual crystallites three-dimensionally, and then the resin precursor was photopolymerized to maintain this orientation. The pseudo single crystal thus obtained produced a well resolved X-ray diffraction profile that is similar to that produced by a twin crystal. The origin of the twin orientation was explained in terms of the interplay between the symmetry of magnetic susceptibility axes and the crystal symmetry (point group 2) of sucrose. The crystal structure of sucrose solved using the pseudo single crystal was in excellent agreement with that solved using a single crystal.

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Palmer, David C. « Digital analysis of X-ray films ». Mineralogical Magazine 61, n^o 406 (juin 1997) : 453–61. http://dx.doi.org/10.1180/minmag.1997.061.406.11.

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AbstractHigh-resolution intensity profiles can be generated from X-ray diffraction films using a desk-top scanner and computer image analysis. The resulting intensity profiles have spatial resolutions equal to, or exceeding that of modern powder diffractometers — at a fraction of the cost. This technique provides an economical way of preserving the information stored in libraries of old (and deteriorating) powder diffraction films. The same technique can also be extended to permit quantitative analysis of single-crystal diffraction films.

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Cusatis, Cesar, Margareth Kobayashi Franco, Edson Kakuno, Carlos Giles, Sergio Morelhão, Vivaldo Mello et Irineu Mazzaro. « A versatile X-ray diffraction station at LNLS (Brazil) ». Journal of Synchrotron Radiation 5, n^o 3 (1 mai 1998) : 491–93. http://dx.doi.org/10.1107/s0909049598000685.

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Versatility was a major consideration in the project to provide an X-ray diffraction station at LNLS. At least two techniques are possible at the station: powder diffraction and multiple single-crystal diffraction. A two-crystal monochromator based on monolithic elastic translators, developed at LNLS, with sagittal focusing by the second crystal, allows 10 mrad of a ≥2 keV monochromatic beam to be used on the diffractometer. The station is equipped with a fast scintillation detector, imaging plates, a high-energy-resolution pin-diode detector, an ionization chamber and a high-angular-resolution soller slit. The data collection and control hardware and software were also developed at LNLS. The θ–2θ goniometry for powder diffraction on this 1 m-diameter diffractometer is based on commercial rotation tables. The multiple single-crystal goniometry is realized by an independent elastic axis driven by differential micrometers for both high- and low-resolution angular movements. At least four independent axes can be positioned as necessary on the diffractometer table. Powder diffractograms and double-crystal rocking curves collected with the synchrotron beam show the expected quality.

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Černý, Radovan, Guillaume Renaudin, Vincent Favre-Nicolin, Viktor Hlukhyy et Rainer Pöttgen. « Mg1 + x Ir1 − x (x = 0, 0.037 and 0.054), a binary intermetallic compound with a new orthorhombic structure type determined from powder and single-crystal X-ray diffraction ». Acta Crystallographica Section B Structural Science 60, n^o 3 (17 mai 2004) : 272–81. http://dx.doi.org/10.1107/s0108768104009346.

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The new binary compound Mg1 + x Ir1 − x (x = 0–0.054) was prepared by melting the elements in the Mg:Ir ratio 2:3 in a sealed tantalum tube under an argon atmosphere in an induction furnace (single crystals) or by annealing cold-pressed pellets of the starting composition Mg:Ir 1:1 in an autoclave under an argon atmosphere (powder sample). The structure was independently solved from high-resolution synchrotron powder and single-crystal X-ray data: Pearson symbol oC304, space group Cmca, lattice parameters from synchrotron powder data a = 18.46948 (6), b = 16.17450 (5), c = 16.82131 (5) Å. Mg1 + x Ir1 − x is a topologically close-packed phase, containing 13 Ir and 12 Mg atoms in the asymmetric unit, and has a narrow homogeneity range. Nearly all the atoms have Frank–Kasper-related coordination polyhedra, with the exception of two Ir atoms, and this compound contains the shortest Ir—Ir distances ever observed. The solution of a rather complex crystal structure from powder diffraction, which was fully confirmed by the single-crystal method, shows the power of powder diffraction in combination with the high-resolution data and the global optimization method.

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Als-Nielsen, Jens. « X-ray powder diffraction for charge density studies ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C1339. http://dx.doi.org/10.1107/s2053273314086604.

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Issues concerning optimal powder diffraction at synchrotron sources for charge density studies will be discussed. These include beam qualities (energy, bandwidth, brillance, flux) as well as sample environmnet (vaccuum, capillary, temperature) and detector type (image plate, crystal analyzer). Simple on-line analysis in obtaining structure factors will be presented.

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