Journal articles: 'Crystal structure'

1

Pushcharovsky, Dmitry Yu, Simon J. Teat, Vyatcheslav N. Zaitsev, Natalia V. Zubkova, and Halil Sarp. "Crystal structure of pushcharovskite." European Journal of Mineralogy 12, no. 1 (February 7, 2000): 95–104. http://dx.doi.org/10.1127/0935-1221/2000/0012-0095.

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Pushcharovsky, Dmitry Y. u., Natalia V. Zubkova, Simon J. Teat, Elizabeth Maclean, and Halil Sarp. "Crystal structure of mahnertite." European Journal of Mineralogy 16, no. 4 (July 15, 2004): 687–92. http://dx.doi.org/10.1127/0935-1221/2004/0016-0687.

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Cattaneo, P. "Crystal structure of La24Ru11." Acta Crystallographica Section E Crystallographic Communications 76, no. 8 (July 3, 2020): 1206–8. http://dx.doi.org/10.1107/s2056989020008695.

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The compound La24Ru11 (tetracosalanthanum undecaruthenium) crystallizes in a Ce24Co11-type structure. The non-centrosymmetric crystal structure (space group P63 mc) contains RuLa6 trigonal prisms, La6 octahedra and LaRu4 tetrahedra and is closely related to that of Ce23Ni7Mg4. This communication highlights the crystal-chemical similarities and points out the differences between the two structures. All of the tested crystals were inversion twins.

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Ali Hakami, Nada Ali, and Hanan Ahmed Hosni Hosni Mahmoud. "Deep Learning Classification of Crystal Structures Utilizing Wyckoff Positions." Crystals 12, no. 10 (October 16, 2022): 1460. http://dx.doi.org/10.3390/cryst12101460.

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In materials science, crystal lattice structures are the primary metrics used to measure the structure–property paradigm of a crystal structure. Crystal compounds are understood by the number of various atomic chemical settings, which are associated with Wyckoff sites. In crystallography, a Wyckoff site is a point of conjugate symmetry. Therefore, features associated with the various atomic settings in a crystal can be fed into the input layers of deep learning models. Methods to analyze crystals using Wyckoff sites can help to predict crystal structures. Hence, the main contribution of our article is the classification of crystal classes using Wyckoff sites. The presented model classifies crystals using diffraction images and a deep learning method. The model extracts feature groups including crystal Wyckoff features and crystal geometry. In this article, we present a deep learning model to predict the stage of the crystal structure–property. The lattice parameters and the structure–property commotion values are used as inputs into the deep learning model for training. The structure–property value of a crystal with a lattice width value of one-half millimeter on average is used for learning. The model attains a considerable increase in speed and precision for the real structure–property prediction. The experimental results prove that our proposed model has a fast learning curve, and can have a key role in predicting the structure–property of compound structures.

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Topa, Dan, Emil Makovicky, Tonči Balić-Žunić, and Peter Berlepsch. "The crystal structure of Cu2Pb6Bi8S19." European Journal of Mineralogy 12, no. 4 (July 17, 2000): 825–33. http://dx.doi.org/10.1127/ejm/12/4/0825.

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Olmi, Filippo, Cesare Sabelli, and Renza Trosti-Ferroni. "The crystal structure of sabelliite." European Journal of Mineralogy 7, no. 6 (December 27, 1995): 1331–38. http://dx.doi.org/10.1127/ejm/7/6/1331.

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Tazzoli, Vittorio, M. Chiara Domeneghetti, Fiοrenzο Mazzi, and Eliο Cannillo. "The crystal structure of chiavennite." European Journal of Mineralogy 7, no. 6 (December 27, 1995): 1339–44. http://dx.doi.org/10.1127/ejm/7/6/1339.

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8

Seryotkin, Yurii V., Vladimir V. Bakakin, and Igor A. Belitsky. "The crystal structure of paranatrolite." European Journal of Mineralogy 16, no. 3 (June 7, 2004): 545–50. http://dx.doi.org/10.1127/0935-1221/2004/0016-0545.

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9

Shilov, Andrey I., Evgeny O. Rakhmanov, Konstantin A. Lyssenko, Alexey N. Kuznetsov, Igor V. Morozov, and Andrei V. Shevelkov. "Crystal and Electronic Structure of Ternary Bismuthides BaTM1.8Bi2 (TM = Au, Ag) with a New Variation of the BaAu2Sb2 Structure Type." Crystals 14, no. 2 (January 31, 2024): 155. http://dx.doi.org/10.3390/cryst14020155.

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Recently discovered bismuthides with the BaAu2Sb2 structure type demonstrate interesting properties and electronic structures. Here, we report successful crystal growth, crystal structure, band structure calculations, and DOS for BaAg1.8Bi2 and BaAu1.8Bi2. Grown crystals were characterized by a combination of single crystal X-ray diffraction and EDX spectroscopy. Both compounds crystallized in a new variation of BaAu2Sb2 structure type and demonstrated metallic properties according to our DFT calculations.

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Choudhury, R. R., R. Chitra, I. P. Makarova, V. L. Manomenova, E. B. Rudneva, A. E. Voloshin, and M. V. Koldaeva. "α-Nickel sulfate hexahydrate crystals: relationship of growth conditions, crystal structure and properties." Journal of Applied Crystallography 52, no. 6 (November 14, 2019): 1371–77. http://dx.doi.org/10.1107/s1600576719013797.

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Studies on α-nickel sulfate hexahydrate (NSH) crystals grown under different conditions are undertaken to investigate how changes in growth conditions affect crystal properties and whether or not there is any modification of the average crystal structure due to changes in crystallization conditions. Thermogravimetric and microhardness studies were carried out on the crystals grown from two different aqueous solutions, one of them containing an excess of sulfuric acid. Raman spectra were recorded and a single-crystal neutron diffraction investigation was conducted on both crystals. A detailed comparison between the two crystal structures and their Raman spectra showed that, although the two crystal structures are very similar, there are slight differences, such as the change in unit-cell volume, differences in the ionic structure, particularly of the sulfate ions, and changes in the hydrogen-bonding network. During solution crystal growth of a salt like NSH, varying the ionic environment around the solute ions influences the interionic interactions between them. Hence it is suggested that the above-mentioned structural differences result from a fine-tuning of the interionic interaction between the cations and anions of NSH in the solution phase. This difference is finally carried over to the crystalline phase. The resulting small crystal structure differences are enough to produce measurable changes in the thermal stability and fragility of the crystals. These differences in crystal properties can be explained on the basis of the observed structural differences between the two crystals grown under different conditions.

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11

Kimata, Mitsuyoshi, Masahiro Shimizu, and Shizuo Saito. "High-temperature crystal structure of sanidine Part II. The crystal structure of sanidine at 935°C." European Journal of Mineralogy 8, no. 1 (February 22, 1996): 15–24. http://dx.doi.org/10.1127/ejm/8/1/0015.

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12

Liu, Zhu, Hu, Dong, and Tan. "Structure, Optical, and Thermal Properties of 9, 10-diphenylanthracene Crystals." Crystals 9, no. 10 (October 1, 2019): 512. http://dx.doi.org/10.3390/cryst9100512.

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9,10-diphenylanthracene (DPA) single crystal is a promising scintillator material for fast-neutron detection. Two centimetre-sized polymorph crystals of DPA were grown by melting and solution methods (DPA-Melt and DPA-Solution, respectively), and characterised by single-crystal X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, fluorescence spectroscopy, UV-Vis absorbance spectroscopy, and thermogravimetric/differential scanning calorimetry. The DPA-Melt crystal possessed a P21/n structure, with excitation bands at approximately 331, 348, 367, and 387 nm, and the strongest emission wavelength at approximately 454 nm. On the other hand, the DPA-Solution crystal possessed a C2/c structure, with excitation bands at approximately 335, 353, 372, and 396 nm, and the strongest emission wavelength at approximately 468 nm. The two kinds of DPA crystals have the same molecular formula but different crystal structures, crystal lattice constants, and cell parameters. The theoretical density of the DPA-Solution crystal was 1.239 g/cm3, while that of the DPA-Melt crystal was 1.211 g/cm3. The two types of crystals exhibited the same melting point, but the thermal stability of the DPA-Solution crystal is better than that of the DPA-Melt crystal.

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13

Murray, Benjamin J., Christoph G. Salzmann, Andrew J. Heymsfield, Steven Dobbie, Ryan R. Neely, and Christopher J. Cox. "Trigonal Ice Crystals in Earth’s Atmosphere." Bulletin of the American Meteorological Society 96, no. 9 (September 1, 2015): 1519–31. http://dx.doi.org/10.1175/bams-d-13-00128.1.

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Abstract We are all familiar with the hexagonal shape of snow and ice crystals, and it is well established that their sixfold symmetry is derived from the arrangement of water molecules in a hexagonal crystal structure. However, atmospheric ice crystals with only threefold rotational symmetry are often observed, which is inconsistent with the hexagonal crystal structure of ordinary ice. These crystals are found in a wide range of different cloud types ranging from upper-tropospheric cirrus to contrails and diamond dust and they form at temperatures ranging from about −84° to −5°C. Recent experimental studies of ice crystal structures have shown that ice under a wide range of atmospheric conditions does not always conform to the standard hexagonal crystal structure. Instead, sequences of the hexagonal structure can be interlaced with cubic sequences to create stacking-disordered ice. This degrades the symmetry of the crystal structure so that, instead of having a hexagonal structure, they have a trigonal structure with a corresponding threefold symmetry. Hence, this implies that atmospheric ice crystals with threefold symmetry are made of stacking-disordered ice. We conclude that the presence of trigonal crystals in the atmosphere is consistent with rare Parry arc halos and also show that they have distinct radiative properties compared with hexagonal ice.

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14

Scaringe, Raymond P. "A priori crystal structure analysis: layer structure." Proceedings, annual meeting, Electron Microscopy Society of America 45 (August 1987): 472–75. http://dx.doi.org/10.1017/s0424820100127062.

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Advances in the theoretical prediction of molecular structure based on molecular mechanics and in the calculation of the lattice energy of molecular crystals with the use of atom-atom potentials have prompted us to examine the problem of a priori crystal structure analysis (i.e., the prediction of crystal structure without the use of diffraction data). A practical solution to this problem would not only represent a significant new tool for theoretical crystallography, but would also open the way to the rational design of molecular solids with engineered structural properties. Potential applications in the areas of solid-state chemistry, optics, and electronics are numerous. In this paper we will describe a complete model for predicting the structure of a 2-dimensional crystal (i.e., a layer). Although the prediction of layer structure is important as a preamble to treating the full 3-dimensional case, molecular layers are also of intrinsic interest.

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15

Hashimoto, Kazumasa, Fumio Sasaki, Shu Hotta, and Hisao Yanagi. "Amplified Emission and Field-Effect Transistor Characteristics of One-Dimensionally Structured 2,5-Bis(4-biphenylyl)thiophene Crystals." Journal of Nanoscience and Nanotechnology 16, no. 4 (April 1, 2016): 3200–3205. http://dx.doi.org/10.1166/jnn.2016.12285.

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One-dimensional (1D) structures of 2,5-bis(4-biphenylyl)thiophene (BP1T) crystals are fabricated for light amplification and field-effect transistor (FET) measurements. A strip-shaped 1D structure (10 m width) made by photolitography of a vapor-deposited polycrystalline film shows amplified spontaneous emission and lasing oscillations under optical pumping. An FET fabricated with this 1D structure exhibits hole-conduction with a mobility of h = 8.0×10−3 cm2/Vs. Another 1D-structured FET is fabricated with epitaxially grown needle-like crystals of BP1T. This needle-crystal FET exhibits higher mobility of h 034 cm2/Vs. This improved hole mobility is attributed to the single-crystal channel of epitaxial needles while the grain boudaries in the polycrystalline 1D-structure decrease the carrier transport.

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16

Žunić, Tončj Balić, Stjepan Šćavničar, and Gianmario Molin. "Crystal structure of prehnite from Komiza." European Journal of Mineralogy 2, no. 5 (October 4, 1990): 731–34. http://dx.doi.org/10.1127/ejm/2/5/0731.

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17

Rømming, Christian, Armen K. Kocharian, and Gunnar Raade. "The crystal structure of kamphaugite-(Y)." European Journal of Mineralogy 5, no. 4 (July 22, 1993): 685–90. http://dx.doi.org/10.1127/ejm/5/4/0685.

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18

V.Seryotkin, Yurii, Werner Joswig, Vladimir V. Bakakin, Igor A. Belitsky, and Boris A. Fursenko. "High-temperature crystal structure of wairakite." European Journal of Mineralogy 15, no. 3 (June 10, 2003): 475–84. http://dx.doi.org/10.1127/0935-1221/2003/0015-0475.

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19

Zubkova, N. V., D. Y. u. Pushcharovsky, G. Ivaldi, G. Ferraris, I. V. Pekov, and N. V. Chukanov. "Crystal structure of natrite, gamma-Na2CO3." Neues Jahrbuch für Mineralogie - Monatshefte 2002, no. 2 (February 8, 2002): 85–96. http://dx.doi.org/10.1127/0028-3649/2002/2002-0085.

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20

Pasero, Marco, and Nicola Rotiroti. "The crystal structure of molybdomenite, PbSeO3." Neues Jahrbuch für Mineralogie - Monatshefte 2003, no. 4 (April 12, 2003): 145–52. http://dx.doi.org/10.1127/0028-3649/2003/2003-0145.

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21

Elking, Dennis M., Laszlo Fusti-Molnar, and Anthony Nichols. "Crystal structure prediction of rigid molecules." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 72, no. 4 (August 1, 2016): 488–501. http://dx.doi.org/10.1107/s2052520616010118.

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A non-polarizable force field based on atomic multipoles fit to reproduce experimental crystal properties andab initiogas-phase dimers is described. The Ewald method is used to calculate both long-range electrostatic and 1/r6dispersion energies of crystals. The dispersion energy of a crystal calculated by a cutoff method is shown to converge slowly to the exact Ewald result. A method for constraining space-group symmetry during unit-cell optimization is derived. Results for locally optimizing 4427 unit cells including volume, cell parameters, unit-cell r.m.s.d. and CPU timings are given for both flexible and rigid molecule optimization. An algorithm for randomly generating rigid molecule crystals is described. Using the correct experimentally determined space group, the average and maximum number of random crystals needed to find the correct experimental structure is given for 2440 rigid single component crystals. The force field energy rank of the correct experimental structure is presented for the same set of 2440 rigid single component crystals assuming the correct space group. A complete crystal prediction is performed for two rigid molecules by searching over the 32 most probable space groups.

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22

AZIMI, GUL MOHAMMAD, ABDUL MANAN HAIRAN, and MOHAMMAD SHAFIQ OMARI. "AB INITIO CALCULATION OF ELECTRONIC STRUCTURE OF SILICON Fd3m and Fm3m." Cognizance Journal of Multidisciplinary Studies 3, no. 8 (August 30, 2023): 832–37. http://dx.doi.org/10.47760/cognizance.2023.v03i08.021.

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Silicon is one of the most famous elements in semiconductor technology, which is used in solar cells, IC, diodes, transistors etc. Silicon has different crystals and amorphous structures, while electronic structures of most of the crystalline are calculated, with experimental and computational methods. These crystallines are made from the same element but have different properties. As the Fd3m and Fm3m crystals with similar Si elements and crystal structure, but with different properties. In this work, we calculated the band structure and PDOS with the DFT method of both crystalline and compare their properties, to what made them different. The band structure shows the band gap of Fd3m is 1.154 eV and for the Fm3m crystal, it is zero. Therefore, the Fd3m crystal is semiconductor and the Fm3m crystal is metal. This discrepancy came from the change in the distance between atoms and the angles at which the atoms are connected.

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23

Ogawa, Shigesaburo, and Isao Takahashi. "Short-Chain Mono-Alkyl β-D-Glucoside Crystals—Do They Form a Cubic Crystal Structure?" Molecules 27, no. 14 (July 7, 2022): 4359. http://dx.doi.org/10.3390/molecules27144359.

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Three-dimensional liquid crystal (LC) phases, cubic LC phases, have been extensively studied as fascinating molecular assembled systems formed by amphiphilic compounds. However, similar structures have only been seen in rare instances in lipid crystal states in glycolipid crystal studies. In this study, we prepared short-chain n-alkyl β-D-glucosides (CnG) with an alkyl chain length n ranging from 4 to 6 and investigated their crystal structures. First, differential thermal analysis (DTA) and thermogravimetric analysis (TG) measurements showed the formation of hydrated crystals for C4G and C5G, respectively. Second, the crystal structures of CnG (n = 4, 5, 6) in both anhydrous and hydrated states were examined using a temperature-controlled powder X-ray diffraction (PXRD) measurement. Both hydrate and anhydrous crystals of C4G and C5G with critical packing parameters (CPPs) less than 0.33 formed cubic crystal phases. Bilayer lengths, calculated from the main diffraction peaks in each PXRD profile, depended on crystalline moisture for C5G, but no significant change was confirmed for C4G, indicating that the properties of each hydrophilic layer differ. However, C6G with a CPP of 0.42 formed a crystal structure with a modulated lamellar structure similar to C7G and C8G with similar CPP values. Thus, a glycolipid motif concept with a cubic crystal structure was demonstrated.

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24

Kainov, Denis E., Vincent Cura, Marc Vitorino, Helène Nierengarten, Pierre Poussin, Bruno Kieffer, Jean Cavarelli, and Arnaud Poterszman. "Structure determination of the minimal complex between Tfb5 and Tfb2, two subunits of the yeast transcription/DNA-repair factor TFIIH: a retrospective study." Acta Crystallographica Section D Biological Crystallography 66, no. 7 (June 19, 2010): 745–55. http://dx.doi.org/10.1107/s0907444910009844.

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Tfb5 interacts with the Tfb2 subunit of the general transcription factor TFIIH to ensure efficient nucleotide-excision repair in eukaryotes. The crystal structure of the complex between Tfb5 and the C-terminal region of Tfb2 (Tfb2C) fromSaccharomyces cerevisiaehas recently been reported. Here, the structure-determination process is described as a case study. Although crystals were obtained readily, it was not possible to determine experimental phases from a first crystal form (Tfb2412–513–Tfb52–72) that diffracted to 2.6 Å resolution. Shortening of the Tfb2C from its N-terminus was decisive and modified the crystal packing, leading to a second crystal form (Tfb2435–513–Tfb52–72). These crystals diffracted to 1.7 Å resolution with excellent mosaicity and allowed structure determination by conventional approaches using heavy atoms. The refined structure from the second crystal form was used to solve the structure of the first crystal form by molecular replacement. Comparison of the two structures revealed that the N-terminal region of Tfb2C and (to a lesser extent) the C-terminal region of Tfb5 contributed to the crystal packing. A detailed analysis illustrates how variation in domain boundaries influences crystal packing and quality.

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Miehe, Gerhard, and Heribert Graetsch. "Crystal structure of moganite: a new structure type for silica." European Journal of Mineralogy 4, no. 4 (August 11, 1992): 693–706. http://dx.doi.org/10.1127/ejm/4/4/0693.

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26

Sokolova, Elena Cámara, Frank C. Hawthorne, and Yassir Abdu. "From structure topology to chemical composition. VII. Titanium silicates: the crystal structure and crystal chemistry of jinshajiangite." European Journal of Mineralogy 21, no. 4 (August 31, 2009): 871–83. http://dx.doi.org/10.1127/0935-1221/2009/0021-1945.

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27

Kitahara, Koichi, Hiroyuki Takakura, Yutaka Iwasaki, and Kaoru Kimura. "Crystal structures of five compounds in the aluminium–ruthenium–silicon system." Acta Crystallographica Section E Crystallographic Communications 79, no. 10 (September 29, 2023): 946–51. http://dx.doi.org/10.1107/s2056989023008393.

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Single crystals of five compounds with approximate compositions ∼Ru16(Al0.78Si0.22)47, (I), ∼Ru9(Al0.70Si0.30)32, (II), ∼Ru10(Al0.67Si0.33)41, (III), ∼Ru(Al0.57Si0.43)5, (IV), and ∼Ru2(Al0.46Si0.54)9, (V), were obtained from polycrystalline lumps mainly composed of the target compounds, and their crystal structures were determined by means of single-crystal X-ray diffraction. The crystal structure of (I) can be related to that of a cubic rational crystalline approximant to an icosahedral quasicrystal through crystallographic shear and then unit-cell twinning. The crystal structure of (II) is isotypic with that of a phase with composition ∼Fe9(Al,Si)32. The crystal structure of (III) is comprised of edge-sharing Ru(Al,Si)9–11 polyhedra with disordered chains along edges of polyhedra. The crystal structure of (IV) is of the LiIrSn4 type. The crystal structure of (V) can be viewed as a crystallographic shear structure derived from that of (IV).

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Flack, Howard D. "Absolute-structure reports." Acta Crystallographica Section C Crystal Structure Communications 69, no. 8 (July 9, 2013): 803–7. http://dx.doi.org/10.1107/s0108270113014789.

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All the 139 noncentrosymmetric crystal structures published inActa Crystallographica Section Cbetween January 2011 and November 2012 inclusive have been used as the basis of a detailed study of the reporting of absolute structure. These structure determinations cover a wide range of space groups, chemical composition and resonant-scattering contribution. DefiningAandDas the average and difference of the intensities of Friedel opposites, their level of fit has been examined using 2ADand selected-Dplots. It was found, regardless of the expected resonant-scattering contribution to Friedel opposites, that the Friedel-difference intensities are often dominated by random uncertainty and systematic error. An analysis of data collection strategy is provided. It is found that crystal-structure determinations resulting in a Flack parameter close to 0.5 may not necessarily be from crystals twinned by inversion. Friedifstatis shown to be a robust estimator of the resonant-scattering contribution to Friedel opposites, very little affected by the particular space group of a structure nor by the occupation of special positions. There is considerable confusion in the text of papers presenting achiral noncentrosymmetric crystal structures. Recommendations are provided for the optimal way of treating noncentrosymmetric crystal structures for which the experimenter has no interest in determining the absolute structure.<!?tpb=25.7pt>

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Øien-Ødegaard, Sigurd, and Karl Lillerud. "Twinning in Zr-Based Metal-Organic Framework Crystals." Chemistry 2, no. 3 (September 16, 2020): 777–86. http://dx.doi.org/10.3390/chemistry2030050.

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Ab initio structure determination of new metal-organic framework (MOF) compounds is generally done by single crystal X-ray diffraction, but this technique can yield incorrect crystal structures if crystal twinning is overlooked. Herein, the crystal structures of three Zirconium-based MOFs, that are especially prone to twinning, have been determined from twinned crystals. These twin laws (and others) could potentially occur in many MOFs or related network structures, and the methods and tools described herein to detect and treat twinning could be useful to resolve the structures of affected crystals. Our results highlight the prevalence (and sometimes inevitability) of twinning in certain Zr-MOFs. Of special importance are the works of Howard Flack which, in addition to fundamental advances in crystallography, provide accessible tools for inexperienced crystallographers to take twinning into account in structure elucidation.

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Alarfaj, Abeer Abdulaziz, and Hanan Ahmed Hosni Mahmoud. "Feature Fusion Deep Learning Model for Defects Prediction in Crystal Structures." Crystals 12, no. 9 (September 19, 2022): 1324. http://dx.doi.org/10.3390/cryst12091324.

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Detection of defective crystal structures can help in refute such defective structures to decrease industrial defects. In our research, we are concerned with Silicon nitride crystals. There are four types of crystal structure classes, namely no-defect structures, pristine crystal structures, defective random displacement crystal structures, and defective 25% vacancies crystal structures. This paper proposes a deep learning model to detect the four types of crystal structures with high accuracy and precision. The proposed model consists of both classification and regression models with a new loss function definition. After training both models, the features extracted are fused and utilized as an input to a perceptron classifier to identify the four types of crystal structures. A novel dense neural network (DNN) is proposed with a multitasking tactic. The developed multitask tactic is validated using a dataset of 16,000 crystal structures, with 30% highly defective crystals. Crystal structure images are captured under cobalt blue light. The multitask DNN model achieves an accuracy and precision of 97% and 96% respectively. Also, the average area under the curve (AUC) is 0.96 on average, which outperforms existing detection methods for crystal structures. The experiments depict the computational time comparison of a single training epoch of our model versus state-of-the-art models. the training computational time is performed using crystal structures diffraction image database of twelve image batches. It can be realized that the prediction computational time of our multitasking model is the least time of 21 s.

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Ogawa, T., S. Isoda, and T. Kobayashi. "Structure Analysis of C60 Low-Temperature Phase by Electron Crystallography with Cryo-TEM." Acta Crystallographica Section B Structural Science 53, no. 5 (October 1, 1997): 831–37. http://dx.doi.org/10.1107/s0108768197005521.

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The crystal structure of C60 at liquid helium temperature was examined by the electron diffraction method using an imaging plate and cryo-TEM (transmission electron microscopy). The crystal of C60 was so thin that the electron scattering from this sample was able to be treated kinematically. However, the least-squares fitting among observed and kinematically calculated diffraction intensities resulted in an R-factor of 0.23 for a structure model with only one major orientation. Similar large R-factors are usually reported in the electron crystallography of thin crystals, in which a single perfect structure was assumed as a model structure. By considering structural disorders in the C60 crystal, however, the R-factor could be reduced to 0.12, when a minor crystal in a different orientation and also the f.c.c. (face-centered cubic) component were introduced to the model in addition to the major orientation crystal. Disorder in the crystal might be as important a factor as the dynamical scattering effect to be considered in electron crystallography for analyzing structures of thin crystals.

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Liu, Li Hua, Ying Bai, Fu Min Wang, and Ning Liu. "Fabrication and Characterizes of TiO₂ Nanomaterials Templated by Lyotropic Liquid Crystal." Advanced Materials Research 399-401 (November 2011): 532–37. http://dx.doi.org/10.4028/www.scientific.net/amr.399-401.532.

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TiO2 nanomaterials were synthesized in lyotropic liquid crystal formed by nonionic surfactant TritonX-100 and TiOSO4 aqueous solution with NH3•H2O as precipitator. The lyotropic liquid crystals were characterized by means of POM and Low-angle XRD. FT-IR, TGA, XRD, TEM were used to characterize the TiO2 samples. It was found that all the lytropic liquid crystal were in lamellar liquid crysal phase and after casting the micro-structure of the LLC phase, the TiO2 samples were self-assemble to form lamellar, sphere and rod structures. According to the characterization results, possible formation mechanism was proposed.

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Zakharov, Boris, Elena Boldyreva, Boris Kolesov, Evgeniy Losev, and Sergey Arkhipov. "Influence of high pressure on amino acids and their multicomponent crystals." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1192. http://dx.doi.org/10.1107/s205327331408807x.

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The studies of molecular crystals at high pressures help to understand intermolecular interactions, their role in the formation of crystal structures and in crystal structure response to external actions. Multicomponent crystals are promising for high-pressure research since a large number of phenomena has been observed for them [1]. Crystals of amino acids, their salts and co-crystals are of special interest in this respect. They are promising as new materials and can serve as biomimetics since the structure forming units of these crystals are similar to those in biomolecules. The aim of this study was to follow the effect of increasing pressure on crystal structures of amino acid salts and co-crystals to compare the results with those obtained for individual amino acids. Glycine, alanine, serine and their corresponding salts with carboxylic acids were chosen as objects of the study. Single-crystal X-ray diffraction and Raman spectroscopy were used as main experimental techniques. Three different types of behavior of salts on increasing pressure as compared with individual crystals were observed. For some salts, adding the second component stabilized the crystal structure with respect to phase transitions [2]. In the second group, on the contrary, the salts underwent phase transitions at relatively low pressures, though individual components did not undergo phase transitions at least up to 8-10 GPa. The last, third group of salts showed phase transitions in a similar pressure range as the individual components, but the mechanism of the transition changed. The phase transitions were accompanied either by crystal structure disordering, or by switching-over hydrogen bonds [3]. This work was supported by a grant from RFBR (12-03-31541 mol_a), by the Ministry of Education and Science of Russia, Russian Academy of Sciences, and by a grant of President of Russia for State support of Russian leading Scientific Schools (project NSh-279.2014.3).

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Yamada, Y., J. Ye, S. Horii, A. Matsushita, and S. Kubo. "Crystal structure in PrBa2Cu4O8 single crystals." Journal of Physics and Chemistry of Solids 62, no. 1-2 (January 2001): 191–94. http://dx.doi.org/10.1016/s0022-3697(00)00126-8.

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Hart, M. "`Perfect' crystals in crystal structure analysis." Acta Crystallographica Section B Structural Science 51, no. 4 (August 1, 1995): 483–85. http://dx.doi.org/10.1107/s0108768195000309.

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Wildner, Manfred, Gerald Giester, Christian L. Lengauer, and Catherine A. Mccammon. "Structure and crystal chemistry of vivianite-type compounds: Crystal structures of erythrite and annabergite with a Mössbauer study of erythrite." European Journal of Mineralogy 8, no. 1 (February 22, 1996): 187–92. http://dx.doi.org/10.1127/ejm/8/1/0187.

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Hostettler, Marc, and Dieter Schwarzenbach. "The structure of orange HgI2. II. Diamond-type structure and twinning." Acta Crystallographica Section B Structural Science 58, no. 6 (November 28, 2002): 914–20. http://dx.doi.org/10.1107/s0108768102016191.

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The metastable orange crystals of HgI_2 comprise three different crystal structures all of which are built from corner-linked Hg_4I_{10} supertetrahedra. Two of the structures are end members with the maximum degree of order (MDO) of a polytypic layer structure. In this paper, the third structure (D) determined from X-ray diffraction, a crystal chemical discussion of the four known tetrahedral HgI_2 structures, and a twinning model are presented. All the various diffraction results published during the past 70 years are now explained. The Hg_4I_{10} supertetrahedra of the tetragonal structure D are corner-linked into two interpenetrating diamond-type networks. The stable red form and the three orange structures show the same cubic densest packing of I atoms and differ only in the distribution of Hg atoms in the tetrahedral voids. Transformations between the structures may involve only movements of Hg atoms, as implied by larger thermal displacement parameters of Hg than of I. A multiply twinned conglomerate of MDO1, MDO2 and D, each structure occurring in three orientations, results in metrically cubic crystals whose Bragg reflections are very close to reciprocal lattice points.

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Bulutoglu, Pelin Su, Conor Parks, Nandkishor K. Nere, Shailendra Bordawekar, and Doraiswami Ramkrishna. "Exploring New Crystal Structures of Glycine via Electric Field-Induced Structural Transformations with Molecular Dynamics Simulations." Processes 7, no. 5 (May 8, 2019): 268. http://dx.doi.org/10.3390/pr7050268.

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Being able to control polymorphism of a crystal is of great importance to many industries, including the pharmaceutical industry, since the crystal’s structure determines significant physical properties of a material. While there are many conventional methods used to control the final crystal structure that comes out of a crystallization unit, these methods fail to go beyond a few known structures that are kinetically accessible. Recent studies have shown that externally applied fields have the potential to effectively control polymorphism and to extend the set of observable polymorphs that are not accessible through conventional methods. This computational study focuses on the application of high-intensity dc electric fields (e-fields) to induce solid-state transformation of glycine crystals to obtain new polymorphs that have not been observed via experiments. Through molecular dynamics simulations of solid-state α -, β -, and γ -glycine crystals, it has been shown that the new polymorphs sustain their structures within 125 ns after the electric field has been turned off. It was also demonstrated that strength and direction of the electric field and the initial structure of the crystal are parameters that affect the resulting polymorph. Our results showed that application of high-intensity dc electric fields on solid-state crystals can be an effective crystal structure control method for the exploration of new crystal structures of known materials and to extend the range of physical properties a material can have.

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Nyman, Jonas, and Graeme Day. "Predicting Porous Molecular Crystals and Clathrates." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1625. http://dx.doi.org/10.1107/s2053273314083740.

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The last decade has seen dramatic improvements in the theories and computer algorithms underlying computational Crystal Structure Predictions [1]. It is now possible to reliably obtain the most likely crystal structures of at least simple molecules starting from nothing more than a drawing of the molecule. We can now go even further and look for rare and exotic kinds of crystals such as porous molecular crystals, clathrates and inclusion compounds among our predictions and calculate their physical properties [2], paving the way for the "science of hypothetical materials". In our poster, we present results on the prediction of fluorophenol xenon clathrates. We have performed crystal structure predictions by global lattice energy searches on o- and m-fluorophenol. The predicted structures have then been analyzed for porosity and their likelihood of being clathrates. From the several thousands of predicted structures, we select a few likely candidates according to an empirical rule based on the guest to host volume ratio [3]. Results from solid state xenon-129 NMR indicate that we have successfully determined the crystal structures of both o- and m-fluorophenol xenon clathrates and we suggest that Crystal Structure Prediction in combination with xenon-129 NMR is a powerful method for determining the structures of clathrates in general.

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Sathishkumar, G., M. Lenin, T. Gubendiran, B. Sathiyamoorthy, S. Nithiyanantham, and P. Ramasamy. "Structural, electrical and optical studies on organic NLO single crystal of N‐benzyl‐2‐methyl‐4‐nitroaniline (BNA)." Vietnam Journal of Chemistry 61, no. 6 (December 2023): 778–87. http://dx.doi.org/10.1002/vjch.202300129.

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AbstractThe 2‐methyl‐4‐nitroaniline (NA) was converted into the raw material N‐benzyl‐2‐methyl‐4‐nitroaniline (BNA), and the solubility of BNA in various organic solvents was calculated gravimetrically. BNA's solubility and crystal structure make it an excellent solvent for the low‐temperature solution growth method used to create single crystals of BNA with orthorhombic structure studied through single crystal analysis. Methanol was used to harvest the 3×10 mm3 BNA single crystals, which are big, translucent yellow crystals. BNA, the subject compound, the exothermic and endothermic nature was characterised by TG analyses, differential scanning calorimeter (DSC), functional studies by infrared (IR) spectra, NMR spectral and optical transmission studies. An Nd:YAG laser (1064 nm) was used to observe the second harmonic generation (SHG) of grown crystal leads about 3 times more than KDP crystal. Possible polarization for various temperatures, the crystal's dielectric properties was measured as a function of frequency. Larger surface morphology with high optical to wave conversion efficiency and the results were reviewed. Responding to electric field to leads to liquid crystal display and THz purposes.

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Wang, Li Hua. "Crystal Structure of 3-Indolepropionic Acid." Applied Mechanics and Materials 454 (October 2013): 272–75. http://dx.doi.org/10.4028/www.scientific.net/amm.454.272.

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The crystals of 3-indolepropionic acid have been obtained by evaporation from ethanol solution. The crystal structure of the 3-indolepropionic acid was determined by X-ray single crystal diffraction analysis. The crystal data for 3-indolepropionic acid: monoclinic, space group P2(1)/c, a = 14.3592(8) Å, b = 5.2446(2) Å, c = 12.3518(6) Å, V = 926.96(8) Å3, Z = 4, Mr = 189.21, De = 1.356 g/cm3, T = 298(2) K, F (000) = 400, R = 0.0435 and wR = 0.1010. The compound forms one-dimensional chained structure through hydrogen bonds and π-π interaction.

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Mykhalichko, Vitaliia, and Roman Gladyshevskii. "Crystal Structure of the Ternary Compound ErRe0.25Ge2." Chemistry & Chemical Technology 10, no. 1 (March 15, 2016): 1–8. http://dx.doi.org/10.23939/chcht10.01.001.

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Ballirano, Paolo, and Adriana Maras. "The crystal structure of a "disordered" cancrinite." European Journal of Mineralogy 16, no. 1 (February 23, 2004): 135–41. http://dx.doi.org/10.1127/0935-1221/2004/0016-0135.

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Laufek, František, Anna Vymazalová, Milan Drábek, Jiří Navrátil, and Jan Drahokoupil. "Synthesis and crystal structure of tischendorfite, Pd8Hg3Se9." European Journal of Mineralogy 26, no. 1 (March 31, 2014): 157–62. http://dx.doi.org/10.1127/0935-1221/2013/0025-2345.

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Han, Yanqiang, Hongyuan Luo, Qianqian Lu, Zeying Liu, Jinyun Liu, Jiarui Zhang, Zhiyun Wei, and Jinjin Li. "Quantum Mechanical-Based Stability Evaluation of Crystal Structures for HIV-Targeted Drug Cabotegravir." Molecules 26, no. 23 (November 26, 2021): 7178. http://dx.doi.org/10.3390/molecules26237178.

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The long-acting parenteral formulation of the HIV integrase inhibitor cabotegravir (GSK744) is currently being developed to prevent HIV infections, benefiting from infrequent dosing and high efficacy. The crystal structure can affect the bioavailability and efficacy of cabotegravir. However, the stability determination of crystal structures of GSK744 have remained a challenge. Here, we introduced an ab initio protocol to determine the stability of the crystal structures of pharmaceutical molecules, which were obtained from crystal structure prediction process starting from the molecular diagram. Using GSK744 as a case study, the ab initio predicted that Gibbs free energy provides reliable further refinement of the predicted crystal structures and presents its capability for becoming a crystal stability determination approach in the future. The proposed work can assist in the comprehensive screening of pharmaceutical design and can provide structural predictions and stability evaluation for pharmaceutical crystals.

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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 (August 5, 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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Shields, Gregory P., Jason C. Cole, Colin R. Groom, Murray G. Read, Ilenia Giangreco, Patrick McCabe, and Anthony M. Reilly. "Generation of crystal structure landscapes using known crystal structures." Acta Crystallographica Section A Foundations and Advances 72, a1 (August 28, 2016): s116. http://dx.doi.org/10.1107/s2053273316098284.

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Zhao, Jianfu, Pengfei Zhu, Zhenyan Wang, Li Ai, Xiulan Duan, and Fapeng Yu. "Growth, Structure and Optical Characterization of Rb3Ti3P5O20 Single Crystal." Materials 15, no. 15 (August 3, 2022): 5346. http://dx.doi.org/10.3390/ma15155346.

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Phosphate crystals attract much attention on account of their rich crystal structures and excellent physical and chemical properties. Herein, Rb3Ti3P5O20 single crystals were grown by the high temperature solution method using Rb2CO3 and NH4H2PO4 as the fluxes. This crystal, with non-centrosymmetric Pca21 space group, presents a three-dimensional framework structure composed of [TiO6] octahedron, [PO4] tetrahedra, and [P2O7] dimers. The electronic structure was measured via X-ray photoelectron spectroscopy. The measurements found that Rb3Ti3P5O20 has stronger Ti–O ionic bonding properties and weaker P–O covalent bonding properties compared to RbTiOPO4. Optical measurements indicated that Rb3Ti3P5O20 has a 3.54 eV band gap and a wide transmission range (0.33–4.5 μm). Theoretical calculations showed that Rb3Ti3P5O20 crystals have a moderate birefringence of 0.079 at 1064 nm. In addition, the relationship of the structure–property was studied using first-principles method. The results demonstrated that TiO6 octahedron played a significant role for the optical properties.

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Mishnev, Anatoly, and Dmitrijs Stepanovs. "Crystal Structure Explains Crystal Habit for the Antiviral Drug Rimantadine Hydrochloride." Zeitschrift für Naturforschung B 69, no. 7 (July 1, 2014): 823–28. http://dx.doi.org/10.5560/znb.2014-4075.

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The crystal structure of the antiviral drug rimantadine hydrochloride, C12H22N+ Cl−, has been elucidated by a single-crystal X-ray structure analysis. The structure consists of 1-(1- adamantyl)ethanamine (rimantadinium) cations and chloride anions. The Cl− anions link the rimantadinium cations via N-H...Cl hydrogen bonds into infinite rectangular chord-like structural units with charged groups in the inner channel and aliphatic groups on the surface, and oriented along the unit cell c axis. In contrast to strong electrostatic and hydrogen bonding inner interactions the chords in the crystal are held together by weak van der Waals forces only. A two-fold symmetry axis passes through the center of the chord. By indexing of the crystal faces it has been shown that the maximal dimension of the needle-like crystals coincides with the direction of the unit cell c axis. These structural features explain the crystal habit and the anisotropy of the mechanical properties of rimantadine hydrochloride crystals observed upon slicing and cleavage.

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Sun, Zhenjie. "Application of third-order nonlinear optical materials in complex crystalline chemical reactions of borates." Nonlinear Engineering 11, no. 1 (January 1, 2022): 609–14. http://dx.doi.org/10.1515/nleng-2022-0234.

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Abstract In order to explore the application of third-order nonlinear optical (NLO) materials in complex borate crystalline chemical reactions, the laser light source with limited wavelength range can be extended to ultraviolet (UV) and deep UV region by using NLO crystal materials and frequency conversion technology, which has become a hot research direction of deep UV light source. The experimental results show that the UV cutoff edge of the grown KLi(HC3N3O3)·2H2O crystal is 237 nm. The refractive index of the crystal was measured by prism coupling technique, and the Sellmeier equation of the refractive index of the crystal was fitted. The chemical bond of the crystal is a fundamental means to understand the relationship between structure and properties. With the emergence of a large number of hybrid functional crystals, the composition and structure of crystals become more complex, and the chemical bond theory has also been greatly developed, and then the chemical bond theory of meta crystals or complex crystals has emerged. Once proposed, the theory has been widely used, such as analyzing the eligibility of luminescent crystals, NLO crystals and high-temperature superconductor crystals. NLO materials are the dominant field of China in the world. Crystals with good nonlinear behavior have more complex crystal structures, due to the theory of amorphous structure, the exploration of this aspect is particularly difficult. For the first time, the influence of the composition of rare earth-doped bismuth borate glass on the crystal precipitation and glass microstructure of NLO materials was systematically studied, which laid a theoretical foundation for further development and understanding of new bismuth borate optical systems.

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Journal articles on the topic 'Crystal structure'

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