301
|
Schaloske MC, Mattausch H, Kienle L, Simon A. Pr10(C2)2Br16: Eine neue Struktur mit diskreten Pr10-Doppeloktaedern. Z Anorg Allg Chem 2008. [DOI: 10.1002/zaac.200800204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
302
|
Schaloske MC, Mattausch H, Kienle L, Simon A. Pr6C2-Doppeltetraeder in Pr6C2Cl10 und Pr6C2Cl5Br5. Z Anorg Allg Chem 2008. [DOI: 10.1002/zaac.200800026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
303
|
Dudka AP, Avilov AS, Lepeshov GG. Crystal structure refinement from electron diffraction data. CRYSTALLOGR REP+ 2008. [DOI: 10.1134/s1063774508030255] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
304
|
Krivanek O, Corbin G, Dellby N, Elston B, Keyse R, Murfitt M, Own C, Szilagyi Z, Woodruff J. An electron microscope for the aberration-corrected era. Ultramicroscopy 2008; 108:179-95. [DOI: 10.1016/j.ultramic.2007.07.010] [Citation(s) in RCA: 261] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2007] [Accepted: 07/05/2007] [Indexed: 11/29/2022]
|
305
|
Characterization of Zirconium Hydrides and Phase Field Approach to a Mesoscopic-Scale Modeling of Their Precipitation. ACTA ACUST UNITED AC 2008. [DOI: 10.1520/jai101161] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
306
|
Morniroli JP, Houdellier F, Roucau C, Puiggalí J, Gestí S, Redjaïmia A. LACDIF, a new electron diffraction technique obtained with the LACBED configuration and a Cs corrector: Comparison with electron precession. Ultramicroscopy 2008; 108:100-15. [PMID: 17517476 DOI: 10.1016/j.ultramic.2007.03.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Revised: 03/12/2007] [Accepted: 03/21/2007] [Indexed: 10/23/2022]
Abstract
By combining the large-angle convergent-beam electron diffraction (LACBED) configuration together with a microscope equipped with a C(s) corrector it is possible to obtain good quality spot patterns in image mode and not in diffraction mode as it is usually the case. These patterns have two main advantages with respect to the conventional selected-area electron diffraction (SAED) or microdiffraction patterns. They display a much larger number of reflections and the diffracted intensity is the integrated intensity. These patterns have strong similarities with the electron precession patterns and they can be used for various applications like the identification of the possible space groups of a crystal from observations of the Laue zones or the ab-initio structure identifications. Since this is a defocused method, another important application concerns the analysis of electron beam-sensitive materials. Successful applications to polymers are given in the present paper to prove the validity of this method with regards to these materials.
Collapse
Affiliation(s)
- J P Morniroli
- Laboratoire de Métallurgie Physique et Génie des Matériaux, UMR CNRS 8517, USTL & ENSCL, Cité Scientifique, 59655 Villeneuve d'Ascq, France.
| | | | | | | | | | | |
Collapse
|
307
|
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.
Collapse
|
308
|
Ciston J, Deng B, Marks LD, Own CS, Sinkler W. A quantitative analysis of the cone-angle dependence in precession electron diffraction. Ultramicroscopy 2007; 108:514-22. [PMID: 17854997 DOI: 10.1016/j.ultramic.2007.08.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2007] [Revised: 06/29/2007] [Accepted: 08/01/2007] [Indexed: 11/26/2022]
Abstract
Precession electron diffraction (PED) is a technique which is gaining increasing interest due to its ease of use and reduction of the dynamical scattering problem in electron diffraction. To further investigate the usefulness of this technique, we have performed a systematic study of the effect of precession angle on the mineral andalusite where the semiangle was varied from 6.5 to 32 mrad in five discrete steps. The purpose of this study was to determine the optimal conditions for the amelioration of kinematically forbidden reflections, and the measurement of valence charge density. We show that the intensities of kinematically forbidden reflections decay exponentially as the precession semiangle (varphi) is increased. We have also determined that charge density effects are best observed at moderately low angles (6.5-13 mrad) even though PED patterns become more kinematical in nature as the precession angle is increased further.
Collapse
Affiliation(s)
- J Ciston
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA.
| | | | | | | | | |
Collapse
|
309
|
Morniroli JP, Redjaimia A. Electron precession microdiffraction as a useful tool for the identification of the space group. J Microsc 2007; 227:157-71. [PMID: 17845710 DOI: 10.1111/j.1365-2818.2007.01800.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The possible space groups of a crystal can be identified from a few zone axis microdiffraction patterns provided the position (and not the intensity) of the reflections on the patterns is taken into account. The method is based on the observation of the shifts and the periodicity differences between the reflections located in the first-order Laue zone (FOLZ) with respect to the ones located in the zero-order Laue zone (ZOLZ). Electron precession microdiffraction patterns display more reflections in the ZOLZ and in the FOLZ than in the conventional microdiffraction patterns and this number increases with the precession angle. It is shown, from the TiAl example given in the present study, that this interesting feature brings a strong beneficial effect for the identification of the possible space groups since it becomes very easy to identify unambiguously the FOLZ/ZOLZ shifts and periodicity differences. In addition, the diffracted intensity on the precession patterns is the integrated intensity and this intensity can also be used to identify the Laue class.
Collapse
Affiliation(s)
- J-P Morniroli
- Laboratoire de Métallurgie Physique et Génie des Matériaux, USTL, ENSCL, CNRS, BâtC(6), Cité Scientifique, 59655 Villeneuve d'Ascq, France.
| | | |
Collapse
|
310
|
Lotsch BV, Döblinger M, Sehnert J, Seyfarth L, Senker J, Oeckler O, Schnick W. Unmasking Melon by a Complementary Approach Employing Electron Diffraction, Solid-State NMR Spectroscopy, and Theoretical Calculations—Structural Characterization of a Carbon Nitride Polymer. Chemistry 2007; 13:4969-80. [PMID: 17415739 DOI: 10.1002/chem.200601759] [Citation(s) in RCA: 397] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Poly(aminoimino)heptazine, otherwise known as Liebig's melon, whose composition and structure has been subject to multitudinous speculations, was synthesized from melamine at 630 degrees C under the pressure of ammonia. Electron diffraction, solid-state NMR spectroscopy, and theoretical calculations revealed that the nanocrystalline material exhibits domains well-ordered in two dimensions, thereby allowing the structure solution in projection by electron diffraction. Melon ([C(6)N(7)(NH(2))(NH)](n), plane group p2 gg, a=16.7, b=12.4 A, gamma=90 degrees, Z=4), is composed of layers made up from infinite 1D chains of NH-bridged melem (C(6)N(7)(NH(2))(3)) monomers. The strands adopt a zigzag-type geometry and are tightly linked by hydrogen bonds to give a 2D planar array. The inter-layer distance was determined to be 3.2 A from X-ray powder diffraction. The presence of heptazine building blocks, as well as NH and NH(2) groups was confirmed by (13)C and (15)N solid-state NMR spectroscopy using (15)N-labeled melon. The degree of condensation of the heptazine core was further substantiated by a (15)N direct excitation measurement. Magnetization exchange observed between all (15)N nuclei using a fp-RFDR experiment, together with the CP-MAS data and elemental analysis, suggests that the sample is mainly homogeneous in terms of its basic composition and molecular building blocks. Semiempirical, force field, and DFT/plane wave calculations under periodic boundary conditions corroborate the structure model obtained by electron diffraction. The overall planarity of the layers is confirmed and a good agreement is obtained between the experimental and calculated NMR chemical shift parameters. The polymeric character and thermal stability of melon might render this polymer a pre-stage of g-C(3)N(4) and portend its use as a promising inert material for a variety of applications in materials and surface science.
Collapse
Affiliation(s)
- Bettina V Lotsch
- Department Chemie und Biochemie, Ludwig-Maximilians-Universität, 81377 München, Germany
| | | | | | | | | | | | | |
Collapse
|
311
|
Sinkler W, Own CS, Marks LD. Application of a 2-beam model for improving the structure factors from precession electron diffraction intensities. Ultramicroscopy 2007; 107:543-50. [PMID: 17240530 DOI: 10.1016/j.ultramic.2006.02.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Accepted: 02/22/2006] [Indexed: 11/26/2022]
|
312
|
Avilov A, Kuligin K, Nicolopoulos S, Nickolskiy M, Boulahya K, Portillo J, Lepeshov G, Sobolev B, Collette J, Martin N, Robins A, Fischione P. Precession technique and electron diffractometry as new tools for crystal structure analysis and chemical bonding determination. Ultramicroscopy 2007; 107:431-44. [PMID: 17258859 DOI: 10.1016/j.ultramic.2006.09.006] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2006] [Accepted: 09/07/2006] [Indexed: 11/29/2022]
|
313
|
Prospects for aberration corrected electron precession. Ultramicroscopy 2007; 107:534-42. [PMID: 17207934 DOI: 10.1016/j.ultramic.2006.03.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2005] [Accepted: 03/08/2006] [Indexed: 11/17/2022]
|
314
|
Dudka AP, Avilov AS, Nicolopoulos S. Crystal structure refinement using Bloch-wave method for precession electron diffraction. Ultramicroscopy 2007; 107:474-82. [PMID: 17222976 DOI: 10.1016/j.ultramic.2006.03.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2006] [Accepted: 03/28/2006] [Indexed: 11/18/2022]
Abstract
Procedure for crystal structure refinement using precession electron diffraction data and Bloch-wave method for accounting multibeam scattering is described. Refinement procedure takes into account features of precession geometry. Refining model consists of structural and reduced parameters determining dynamic diffraction. Difference between measured and calculated dynamic intensities of reflections is minimized with application of a nonlinear least squares method. As test example we used Si single nanocrystals. The influence of the reduced parameters on the quality of the obtained model is discussed. Refinement procedure is a part of ASTRA software.
Collapse
Affiliation(s)
- A P Dudka
- Institute of Crystallography of Russian Academy of Sciences, Leninsky prosprect 59, Moscow 119333, Russia
| | | | | |
Collapse
|
315
|
Boulahya K, Ruiz-González L, Parras M, González-Calbet JM, Nickolsky MS, Nicolopoulos S. Ab initio determination of heavy oxide perovskite related structures from precession electron diffraction data. Ultramicroscopy 2007; 107:445-52. [PMID: 17254714 DOI: 10.1016/j.ultramic.2006.03.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2005] [Accepted: 03/23/2006] [Indexed: 11/22/2022]
Abstract
Two complex perovskite-related structures were solved by ab initio from precession electron diffraction intensities. Structure models were firstly derived from HREM images and than have been confirmed independently using two and three-dimensional sets of precession intensities. Patterson techniques prove to be effective for ab initio structure resolution, specially in case of projections with no overlapping atoms. Quality of precession intensity data may be suitable enough to resolve unknown heavy oxide structures.
Collapse
Affiliation(s)
- Khalid Boulahya
- Dpto. Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, E28040 Madrid, Spain
| | | | | | | | | | | |
Collapse
|
316
|
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]
|
317
|
Gemmi M, Nicolopoulos S. Structure solution with three-dimensional sets of precessed electron diffraction intensities. Ultramicroscopy 2007; 107:483-94. [DOI: 10.1016/j.ultramic.2006.03.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Accepted: 03/09/2006] [Indexed: 11/24/2022]
|
318
|
Morniroli J, Redjaïmia A, Nicolopoulos S. Contribution of electron precession to the identification of the space group from microdiffraction patterns. Ultramicroscopy 2007; 107:514-22. [DOI: 10.1016/j.ultramic.2006.03.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2005] [Accepted: 03/29/2006] [Indexed: 11/24/2022]
|
319
|
He H, Nelson C. A method of combining STEM image with parallel beam diffraction and electron-optical conditions for diffractive imaging. Ultramicroscopy 2007; 107:340-4. [PMID: 17079081 DOI: 10.1016/j.ultramic.2006.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2006] [Revised: 09/13/2006] [Accepted: 09/20/2006] [Indexed: 11/17/2022]
Abstract
We describe a method of combining STEM imaging functionalities with nanoarea parallel beam electron diffraction on a modern TEM. This facilitates the search for individual particles whose diffraction patterns are needed for diffractive imaging or structural studies of nanoparticles. This also lays out a base for 3D diffraction data collection.
Collapse
Affiliation(s)
- Haifeng He
- Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504, USA.
| | | |
Collapse
|
320
|
|
321
|
Precession electron diffraction: observed and calculated intensities. Ultramicroscopy 2007; 107:523-33. [PMID: 17291687 DOI: 10.1016/j.ultramic.2006.04.032] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2006] [Accepted: 04/22/2006] [Indexed: 11/30/2022]
Abstract
Theory and algorithms have been developed for performing kinematical and dynamical two-beam and multibeam dynamical simulations of precession electron diffraction patterns. Intensities in experimental precession patterns have been quantified and are shown to be less dynamical.
Collapse
|
322
|
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.
Collapse
|
323
|
Kverneland A, Hansen V, Vincent R, Gjønnes K, Gjønnes J. Structure analysis of embedded nano-sized particles by precession electron diffraction. η′-precipitate in an Al–Zn–Mg alloy as example. Ultramicroscopy 2006; 106:492-502. [PMID: 16564629 DOI: 10.1016/j.ultramic.2006.01.009] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2005] [Revised: 01/09/2006] [Accepted: 01/19/2006] [Indexed: 11/25/2022]
Abstract
The Vincent-Midgley precession technique has been used to collect three-dimensional electron diffraction intensity data from a dispersion of coherent precipitates in a matrix. In order to suppress severe effects from multiple diffraction via matrix reflections, a fairly large precession (tilt) angle had to be used. This implied a high background from the surrounding matrix, and limited the number of reflections that could be measured from patterns on image plates. The heavily faulted hexagonal eta'-precipitates (a = 0.496 nm, c = 1.405 nm) with thickness 3-5 nm occur in four equivalent orientations relative to the aluminium matrix; with frequent overlap of reflections. A model of the average structure in the space group P6(3)/mmc with assumed composition Mg(2)Zn(5-x)Al(2+x), have been derived by Patterson analysis and intensity comparisons.
Collapse
Affiliation(s)
- A Kverneland
- Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, N-4036 Stavanger, Norway.
| | | | | | | | | |
Collapse
|
324
|
Weirich TE, Portillo J, Cox G, Hibst H, Nicolopoulos S. Ab initio determination of the framework structure of the heavy-metal oxide CsxNb2.54W2.46O14 from 100kV precession electron diffraction data. Ultramicroscopy 2006; 106:164-75. [PMID: 16137828 DOI: 10.1016/j.ultramic.2005.07.002] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Revised: 07/06/2005] [Accepted: 07/08/2005] [Indexed: 11/17/2022]
Abstract
The present work deals with the ab initio determination of the heavy metal framework in Cs(x)(Nb, W)(5)O(14) from precession electron diffraction intensities. The target structure was first discovered by Lundberg and Sundberg [Ultramicroscopy 52 (1993) 429-435], who succeeded in deriving a tentative structural model from high-resolution electron microsopy (HREM) images. The metal framework of the compound was solved in this investigation via direct methods from hk0 precession electron diffraction intensities recorded with a Philips EM400 at 100 kV. A subsequent (kinematical) least-squares refinement with electron intensities yielded slightly improved co-ordinates for the 11 heavy atoms in the structure. Chemical analysis of several crystallites by EDX is in agreement with the formula Cs(0.44)Nb(2.54)W(2.46)O(14). Moreover, the structure was independently determined by Rietveld refinement from X-ray powder data obtained from a multi-phasic sample. The compound crystallises in the orthorhombic space group Pbam with refined lattice parameters a=27.145(2), b=21.603(2), and c=3.9463(3)A. Comparison of the framework structure from electron diffraction with the result from Rietveld refinement shows an average agreement for the heavy atoms within 0.09 A.
Collapse
Affiliation(s)
- Thomas E Weirich
- Gemeinschaftslabor für Elektronenmikroskopie der Rheinisch-Westfälischen Technischen Hochschule (RWTH) Aachen, Ahornstrasse 55, Aachen D-52074, Germany.
| | | | | | | | | |
Collapse
|
325
|
Dorset DL, Weston SC, Dhingra SS. Crystal Structure of Zeolite MCM-68: A New Three-Dimensional Framework with Large Pores. J Phys Chem B 2006; 110:2045-50. [PMID: 16471781 DOI: 10.1021/jp0565352] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The crystal structure of the aluminosilicate MCM-68 was solved from synchrotron powder diffraction data by the program FOCUS. The unit cell framework contains Si100.6Al11.4O224. This material crystallizes in space group P42/mnm, where, after Rietveld refinement, a=18.286(1) A and c=20.208(2) A. A three-dimensional framework is found that contains continuous 12-ring channels and two orthogonal, intersecting, undulating 10-ring channels. Rietveld refinement of the model coordinates optimizes the framework geometry, to match the observed intensity profile by Rwp=0.1371, R(F2)=0.1411. It is not possible to determine the location of approximately 0.84 K+ cations remaining in the unit cell after the material is steamed and then dehydrated. The framework model also successfully predicts observed electron diffraction data in two projections, and the tetragonal projection can be determined independently from these data by direct methods. The calculated density of the framework structure is 1.66 g/cm3, and the T-site framework density is 16.6 T/1000 A3.
Collapse
Affiliation(s)
- Douglas L Dorset
- Corporate Strategic Research, ExxonMobil Research and Engineering Co., 1545 Route 22 East, Annandale, New Jersey 08801, USA.
| | | | | |
Collapse
|
326
|
Own CS, Sinkler W, Marks LD. Rapid structure determination of a metal oxide from pseudo-kinematical electron diffraction data. Ultramicroscopy 2005; 106:114-22. [PMID: 16125847 DOI: 10.1016/j.ultramic.2005.06.058] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Revised: 06/13/2005] [Accepted: 06/22/2005] [Indexed: 12/01/2022]
Abstract
The electron precession diffraction technique is employed to provide quasi-kinematical data for determination of atom positions in the (Ga,In)2SnO5m-phase. Precession data are compared with conventional diffraction data captured under identical conditions and show a distinct superiority because they exhibit kinematical characteristics in the structure-defining reflections. Precessed data are not usable within a kinematical interpretation in all cases, and a simple basis is presented for omission of errant reflections to improve adherence to kinematical behavior. A second approach is demonstrated where intensities are used with direct methods instead of amplitudes, enhancing the contrast between strong and weak beams. The unrefined atom positions recovered a priori via direct methods are consistent between the two approaches and fall on average within 4 picometers of positions in the previously refined structure.
Collapse
Affiliation(s)
- C S Own
- Department of Materials Science, Northwestern University, 2220 Campus Dr., Cook 2036, Evanston, IL 60208, USA.
| | | | | |
Collapse
|
327
|
Gjønnes J, Hansen V, Kverneland A. The precession technique in electron diffraction and its application to structure determination of nano-size precipitates in alloys. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2004; 10:16-20. [PMID: 15306062 DOI: 10.1017/s1431927604040279] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2003] [Indexed: 05/24/2023]
Abstract
Crystal structure of nano-scale precipitates in age-hardening aluminum alloys is a challenge to crystallography. The utility of selected area electron diffraction intensities from embedded precipitates is limited by double scattering via matrix reflections. This effect can be signally reduced by the precession technique, which we have used to collect extensive intensity data from the semicoherent, metastable eta-precipitate in the Al-Zn-Mg alloy system. A structure model in the space group P-62c is proposed from high-resolution microscopy and electron diffraction intensities. The advantages of using the precession technique for quantitative electron diffraction is discussed.
Collapse
Affiliation(s)
- J Gjønnes
- Center for Materials Science, University of Oslo, Gaustadalleen 21, N-0349 Oslo, Norway.
| | | | | |
Collapse
|
328
|
Own CS, Subramanian AK, Marks LD. Quantitative analyses of precession diffraction data for a large cell oxide. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2004; 10:96-104. [PMID: 15306071 DOI: 10.1017/s1431927604040322] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2003] [Indexed: 05/24/2023]
Abstract
Kinematical and two-beam calculations have been conducted and are compared to experimental precession data for the large unit cell crystal La4Cu3MoO12. Precession electron diffraction intensities are found to exhibit approximate two-beam behavior and demonstrate clear advantages over conventional SADP intensities for use in structure solution.
Collapse
Affiliation(s)
- Christopher S Own
- Department of Materials Science, Northwestern University, 2220 N. Campus Dr., Cook 2036, Evanston, IL 60201, USA.
| | | | | |
Collapse
|
329
|
Jansen J, Zandbergen HW, Otten MT. The effect of inelastic scattering on crystal structure refinement from electron diffraction patterns recorded under almost parallel illumination. Ultramicroscopy 2004; 98:165-72. [PMID: 15046796 DOI: 10.1016/j.ultramic.2003.08.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2003] [Revised: 07/20/2003] [Indexed: 10/27/2022]
Abstract
Recently a number of crystal structures were determined using electron diffraction data with an almost parallel electron beam. In many cases no energy filtering was applied. On the other hand, the contrast in convergent beam electron diffraction patterns is greatly improved by energy filtering of the electrons. To investigate whether energy filtering will improve the accuracy of the structure analysis from diffraction data recorded under an almost parallel beam condition, we recorded diffraction patterns of the [100] zone of YBa(2)Cu(3)O(7) using unfiltered electrons, zero-loss electrons and plasmon-loss electrons, respectively. Subsequently, the structure is refined based on these different electron diffraction datasets, using the program MSLS (Acta Crystallogr. A 54 (1998) 91). The results show that the obtained atomic positions are not significantly different for the chosen filter conditions. Even with amorphous carbon deposited on the specimen, which will cause a significant increase (>40 times) of energy-loss electrons, the structure refinement led to the same atomic positions.
Collapse
Affiliation(s)
- J Jansen
- Department of Nanoscience, Laboratory of Materials Science, Delft University of Technology, National Centre for HREM, Rotterdamseweg 137, Delft 2628 AL, The Netherlands.
| | | | | |
Collapse
|
330
|
Hovmöller S, Zou X, Weirich TE. Crystal structure determination from EM images and electron diffraction patterns. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1076-5670(02)80066-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
|
331
|
|
332
|
Strategies in electron diffraction data collection. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1076-5670(02)80068-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
333
|
Abstract
Among different techniques, electron crystallography presents the advantage to determine structures on a local scale or from very small samples. Different methods such as image processing, exit wave reconstruction, Patterson analysis, or direct methods can be applied for getting a starting structural model. Results obtained on various oxides have shown that the dynamical nature of electron scattering, far from being detrimental, can even help in the localization of oxygen atoms close to heavier scatters. Concerning the structure refinement step, it is now possible to introduce dynamical effect correction through multislice calculations combined with least-squares refinement. However, depending on the problem to solve and the accuracy needed, the alternative solution consisting in getting as close as possible to kinematical conditions is still worth considering. Different examples of structures refined from electron diffraction data are given.
Collapse
|
334
|
Belletti D, Calestani G, Gemmi M, Migliori A. QED v 1.0: a software package for quantitative electron diffraction data treatment. Ultramicroscopy 2000; 81:57-65. [PMID: 10998791 DOI: 10.1016/s0304-3991(99)00118-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
A new software package for quantitative electron diffraction data treatment of unknown structures is described. No "a priori" information is required by the package which is able to perform in successive steps the 2-D indexing of digitised diffraction patterns, the extraction of the intensity of the collected reflections and the 3-D indexing of all recorded patterns, giving as results the lattice parameters of the investigated structure and a series of data files (one for each diffraction pattern) containing the measured intensities and the relative e.s.d.s of the 3-D indexed reflections. The software package is mainly conceived for the treatment of diffraction patterns taken with a Gatan CCD Slow-Scan Camera, but it can also deal with generic digitised plates. The program is designed to extract intensity data suitable for structure solution techniques in electron crystallography. The integration routine is optimised for a correct background evaluation, a necessary condition to deal with weak spots of irregular shape and an intensity just above the background.
Collapse
Affiliation(s)
- D Belletti
- Dipartimento di Chimica Generale ed Inorganica, Università di Parma, Italy
| | | | | | | |
Collapse
|
335
|
|
336
|
Berg B, Hansen V, Midgley P, Gjønnes J. Measurement of three-dimensional intensity data in electron diffraction by the precession technique. Ultramicroscopy 1998. [DOI: 10.1016/s0304-3991(98)00038-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
337
|
Gjønnes K. On the integration of electron diffraction intensities in the Vincent-Midgley precession technique. Ultramicroscopy 1997. [DOI: 10.1016/s0304-3991(97)00031-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|