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Eggeman AS, Barnard JS, Midgley PA. Aberration-corrected and energy-filtered precession electron diffraction. Z KRIST-CRYST MATER 2013. [DOI: 10.1524/zkri.2013.1565] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Šišak D, Baerlocher C, McCusker LB, Gilmore CJ. Optimizing the input parameters for powder charge flipping. J Appl Crystallogr 2012. [DOI: 10.1107/s0021889812040411] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Over the past few years, the powder charge-flipping algorithm has proved to be a useful one for structure solution from powder diffraction data, so a semi-systematic study of the effect of the different input parameters on its success has been performed. Two data sets were studied in these tests: a zirconium phosphate framework material and D-ribose. TheSuperflipinput parameters tested were the reflection overlap factor, the intensity repartitioning frequency, the isotropic displacement parameter, the threshold for charge flipping and the number of cycles/runs. By varying the values of these parameters within sensible ranges, an optimized set could be found for the zirconium phosphate case, but no combination of parameters allowed the D-ribose structure to be solved. Reasoning that starting with nonrandom phases might help, an approximate (but incorrect) structure was generated using the direct-space global-optimization method implemented in the programFOX. This structure was then used to calculate initial phase sets forSuperflipby allowing the calculated phases to vary in a random fashion by a user-defined percentage. With such phases and reoptimized input parameters, some fully interpretable solutions with the correct symmetry could be produced, even with fairly low resolution data. Unfortunately, it was not possible to recognize these solutions using theSuperflip Rvalues, so other criteria were sought. Both cluster analyses and maximum entropy calculations of the solutions were performed, and the latter, in particular, look very promising. A set of guidelines derived from these two structures could be applied successfully to a further two inorganic and seven organic structures.
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Abstract
It is shown that it is possible to obtain structural information from small (<100 nm) phthalocyanine crystals by using crystallographic direct phasing methods applied to electron diffraction data. This technique is both quantitative and does not suffer from the difficulties associated with high-resolution electron microscopy. Structural information has been obtained from both tetra- and octa chloro-copper phthalocyanines, and the results compared with the hydrogenated and perchloro members of the series.
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Affiliation(s)
- J. R. FRYER
- Chemistry Department, University of Glasgow, Glasgow G12 8QQ, UK
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Dorset DL, Baugh LS, Luo J, Shea KJ. Rectangular Chain Packing of Methyl-Branched Paraffins: Persistence of an Interchain Interaction and Forms of Disorder. J Phys Chem B 2011; 115:8858-63. [DOI: 10.1021/jp202495p] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Douglas L. Dorset
- ExxonMobil Research and Engineering, Corporate Strategic Research Laboratory, 1545 Route 22 East, Annandale, New Jersey 08801, United States
| | - Lisa Saunders Baugh
- ExxonMobil Research and Engineering, Corporate Strategic Research Laboratory, 1545 Route 22 East, Annandale, New Jersey 08801, United States
| | - Jun Luo
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Kenneth J. Shea
- Department of Chemistry, University of California, Irvine, California 92697, United States
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Abstract
Abstract
Given that many zeolites crystallize in habits that lead to preferred orientation, and that there is a ±60° tilt limitation in many electron microscope goniometer stages, collection of a three 3-D electron diffraction data set from these materials is severely restricted. To overcome this, preparative measures must be taken to produce other sample orientations. Using a number of MWW framework zeolites (MCM-22, MCM-22P, MCM-49, ITQ-1) as examples, thin-sectioned views onto the edge stacking of lamellar layers can be prepared by a number of methods. While ultamicrotomy is a traditional approach to this problem, sections are often very thick and sparsely distributed. Other extreme mechanical processing techniques, such as extrusion and jet milling produce numerous thin crystals with the desired orientation. Dealumination, initiated by steaming, calcination or low pH, also yields a similar result. Additional intensity data from the ‘missing cone’ in addition to those obtained by tilting hexagonal plate crystals provides a more complete data set and hence a more easily interpreted structure analysis. Crystallographic phase determination by maximum entropy and likelihood, followed by Fourier refinement, yields a structural model very close to that of the known MWW framework.
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Thomas J, Midgley P. The Merits of Static and Dynamic High-Resolution Electron Microscopy (HREM) for the Study of Solid Catalysts. ChemCatChem 2010. [DOI: 10.1002/cctc.201000059] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Gjønnes J, Hansen V, Andersen SJ, Marioara CD, Li XZ. Electron crystallography of aluminum alloy phases. ACTA ACUST UNITED AC 2009. [DOI: 10.1524/zkri.218.4.293.20745] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
A series of structure analyses during 1994-2001 by electron crystallographic techniques applied to phases in aluminum alloys are reviewed. Methods for structure solution employ electron diffraction intensity data collected by the precession technique, by selected area micro-diffraction and by the convergent-beam technique. High-resolution electron microscope images (HRTEM) are treated by different kind of processing, including exit wave reconstruction. Crystallographic calculations are performed either by direct method or Patterson and Fourier procedures, assuming kinematical scattering, or by refinement from models derived from HRTEM images. Dynamical scattering calculations can be introduced in the refinement stage or as a correction procedure applied to part of the intensity data. The phases studied include primary Al-Fe-(Si) particles, Al-Mn-Si dispersoids, Al-Co quasicrystals and two types of precipitate phases in age-hardening Al-Mg-Si and Al-Zn-Mg alloys.
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Abstract
Abstract
Organic materials, such as non-linear optical active compounds (1-(2-furyl)-3-(4-aminophenyl)-2-propene-1-one (FBAPPO) and 1-(2-furyl)-3-(4-benzamidophenyl)-2-propene-1-one (FAPPO)), polymeric materials like the metal coordinated polyelectrolyte (Fe(II) [ditopic bis-terpyridin] (MEPE)) or polymorphic materials (e.g. Cu-phthalocyanine), which do not crystallize big enough for single crystal x-ray structure analysis have been investigated by electron diffraction (ED) at 100 and 300 kV acceleration voltage. Sample preparation (direct crystallization, ultra sonication, ultra microtomy), diffraction strategies (selected area diffraction, nano diffraction, use of double-tilt rotation holder), data collection and data processing as well as structure solution strategies have been chosen dependent on the different requirements of the compounds under investigation. Structure analysis was carried out by simulation using ab initio quantum-mechanical methods like density functional theory (DFT), semi-empirical approach (MNDO/AM1/PM3) and force field packing energy calculations (DREIDING). The structure models resulting from simulation were refined kinematically as rigid bodies. Subsequently, refinements by multi-slice least squares (MSLS) procedures taking dynamical scattering into account were performed. The described combination of different methods which was used successfully on crystallizable materials is also adaptable to insoluble organic materials (e.g. pigments) and polymorphic systems.
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Zou X, Hovmöller S. Electron crystallography: imaging and single-crystal diffraction from powders. Acta Crystallogr A 2007; 64:149-60. [DOI: 10.1107/s0108767307060084] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Accepted: 11/16/2007] [Indexed: 11/10/2022] Open
Abstract
The study of crystals at atomic level by electrons – electron crystallography – is an important complement to X-ray crystallography. There are two main advantages of structure determinations by electron crystallography compared to X-ray diffraction: (i) crystals millions of times smaller than those needed for X-ray diffraction can be studied and (ii) the phases of the crystallographic structure factors, which are lost in X-ray diffraction, are present in transmission-electron-microscopy (TEM) images. In this paper, some recent developments of electron crystallography and its applications, mainly on inorganic crystals, are shown. Crystal structures can be solved to atomic resolution in two dimensions as well as in three dimensions from both TEM images and electron diffraction. Different techniques developed for electron crystallography, including three-dimensional reconstruction, the electron precession technique and ultrafast electron crystallography, are reviewed. Examples of electron-crystallography applications are given. There is in principle no limitation to the complexity of the structures that can be solved by electron crystallography.
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Dorset DL, Gilmore CJ, Jorda JL, Nicolopoulos S. Direct electron crystallographic determination of zeolite zonal structures. Ultramicroscopy 2007; 107:462-73. [DOI: 10.1016/j.ultramic.2006.05.013] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2005] [Accepted: 05/06/2006] [Indexed: 11/16/2022]
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Electron crystallography of organic materials. Ultramicroscopy 2006; 107:453-61. [PMID: 17240070 DOI: 10.1016/j.ultramic.2006.03.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Accepted: 03/09/2006] [Indexed: 11/30/2022]
Abstract
The application of electron crystallography to the study of organic materials is reviewed, mainly in context of the author's own experience. Direct methods for crystallographic phase determination have been shown to be very effective for ab initio structure analyses with electron diffraction intensities, permitting the elucidation of previously uncharacterized crystal structures. Fruitful applications areas have included chain-folded linear polymers, pigments, polydisperse linear chain arrays and, surprisingly, the subgroup assembly of certain proteins.
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Comparison of electron diffraction data from non-linear optically active organic DMABC crystals obtained at 100 and 300 kV. Ultramicroscopy 2000; 83:33-59. [PMID: 10805391 DOI: 10.1016/s0304-3991(99)00166-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
During the recent past, we have synthesized a new class of molecules with intramolecular two-dimensional charge transfer upon excitation. The present report presents such a molecule, 2,6-bis(4-dimethylamino-benzylidene)-cyclohexanone (DMABC), with an unusually high value of the second-order non-linear optical (NLO) coefficients. In order to optimize the macroscopic NLO properties of the compounds, it is necessary to relate their first hyperpolarizability tensors at a molecular level to those at a crystal bulk level. This requires a complete structure determination and refinement. However, the growth of sufficiently large single crystals, which are needed for structural analysis and refinement by X-ray methods, is a time consuming and sometimes impossible task. We have performed a complete structural analysis by electron diffraction combined with simulation methods and with maximum entropy and log likelihood statistics. In order to improve the quantitative analysis, a 300 kV data set using an on-line CCD camera was added and the best attainable R-values were compared with those from 100 kV data using film emulsions. Details regarding the maximum attainable resolution for both data sets are discussed as well as the problems which arise from the limited dynamic range in photographic emulsions as compared to a 14 bit CCD camera. Once the crystal structure was known, quantum-chemical methods were used to calculate non-linear optical susceptibility tensor components and these were related to the macroscopic coefficients of the crystalline quadratic non-linearity tensor. In the present work, both ab initio and semi-empirical quantum-chemical calculations were employed.
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Leslie C, Landree E, Collazo-Davila C, Bengu E, Grozea D, Marks LD. Electron crystallography in surface structure analysis. Microsc Res Tech 1999; 46:160-77. [PMID: 10420173 DOI: 10.1002/(sici)1097-0029(19990801)46:3<160::aid-jemt2>3.0.co;2-#] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Surface structure analysis is an important area of research, and in recent years notable advances have been made in this field, both in improved techniques for studying surfaces and in methods of analyzing them. This review aims to summarize the techniques available, particularly those relating to electron microscopy, and also to outline one of the newest areas of development, the application of direct methods to surface structure analysis.
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Affiliation(s)
- C Leslie
- Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
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Abstract
Electron crystallography can be used to obtain specific information about molecular parameters such as the polarisability, dipole moment, and hyperpolarisability. In this, work we show how a combination of quantum mechanics and simulation methods can be used to solve several unknown organic structures and how the calculated molecular parameters can be used to predict the corresponding physical properties of the crystals.
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Affiliation(s)
- I G Voigt-Martin
- Institut für Physikalische Chemie der Universität Mainz, D 55099 Mainz, Germany.
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Affiliation(s)
- C. Leslie
- Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208
| | - E. Landree
- Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208
| | - C. Collazo‐Davila
- Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208
| | - E. Bengu
- Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208
| | - D. Grozea
- Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208
| | - L. D. Marks
- Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208
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Abstract
The maximum entropy (ME) method of solving crystal structures in two or three dimensions from electron diffraction data is described. Applications to organic and inorganic molecules, membrane proteins and surface structures are outlined, and the power of the ME formalism to deal with incomplete and error prone data is demonstrated.
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Affiliation(s)
- C J Gilmore
- Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom.
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Poojary DM, Clearfield A. Application of X-ray Powder Diffraction Techniques to the Solution of Unknown Crystal Structures. Acc Chem Res 1997. [DOI: 10.1021/ar960143j] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Damodara M. Poojary
- Department of Chemistry, Texas A & M University, College Station, Texas 77843
| | - Abraham Clearfield
- Department of Chemistry, Texas A & M University, College Station, Texas 77843
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The use of maximum entropy statistics combined with simulation methods to determine the structure of 4-dimethylamino-3-cyanobiphenyl. Ultramicroscopy 1997. [DOI: 10.1016/s0304-3991(97)00006-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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[23] Bayesian statistical viewpoint on structure determination: Basic concepts and examples. Methods Enzymol 1997; 276:361-423. [PMID: 27799106 DOI: 10.1016/s0076-6879(97)76069-5] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Applications of the maximum entropy method to powder diffraction and electron crystallography. ACTA ACUST UNITED AC 1997. [DOI: 10.1098/rspa.1993.0093] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A new multisolution phasing method based on entropy maximization and likelihood ranking, proposed for the specific purpose of increasing the accuracy and sensitivity of probabilistic phase indications compared with conventional direct methods, has been implemented and applied to a wide variety of problems. The latter comprise the determination of small crystal structures from X-ray diffraction data obtained from single crystals or from powders, and from electron diffraction data, both with and without partial phase information obtained by image processing of electron micrographs; the ranking of phase sets for a small protein; and the improvement of poor quality phases for a larger protein at medium resolution under constraint of solvent flatness. The main components of the method are (1) a tree-directed search through a space of trial phase sets; (2) the saddlepoint method for calculating joint probabilities of structure factors, using entropy maximization; (3) likelihood-based scores to rank trial phase sets and prune the search tree; (4) a statistical analysis of the scores for automatically selecting reliable phase indications. Their use is illustrated here on structure determinations from powder X-ray diffraction data and from electron diffraction data.
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The use of maximum entropy and likelihood ranking to determine the crystal structure of 4-(4′-(N,N-dimethyl)aminobenzylidene)-pyrazolidine-3,5-dione at 1.4 Å resolution from electron diffraction and high-resolution electron microscopy image data. Ultramicroscopy 1994. [DOI: 10.1016/0304-3991(94)90014-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Brünger AT, Nilges M. Computational challenges for macromolecular structure determination by X-ray crystallography and solution NMR-spectroscopy. Q Rev Biophys 1993; 26:49-125. [PMID: 8210313 DOI: 10.1017/s0033583500003966] [Citation(s) in RCA: 135] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Macromolecular structure determination by X-ray crystallography and solution NMR spectroscopy has experienced unprecedented growth during the past decade.
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Affiliation(s)
- A T Brünger
- Howard Hughes Medical Institute, Yale University, New Haven, CT 06511
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Phase extension in electron crystallography using the maximum-entropy method and its application to two-dimensional purple membrane data from Halobacterium halobium. Ultramicroscopy 1993. [DOI: 10.1016/0304-3991(93)90220-r] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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