Dynamical Structure Factors for Bent Organic Crystals

1982 ◽  
Vol 40 ◽  
pp. 94-95
Author(s):  
Barbara Moss ◽  
Douglas L. Dorset
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Electron Diffraction Data ◽  
Dynamical Structure ◽  
Organic Crystals ◽  
Beam Direction ◽  
Scattering Intensity ◽  
X Ray ◽  
Structure Factors ◽  
Long Chain

The success of quantitative crystal structure determination from electron diffraction data requires a valid analysis of the observed intensities. Traditional X-ray crystallographic techniques rely on the kinematic scattering model. However, some organic microcrystals exhibit significant dynamical scattering from extremely thin specimens and crystal bending further complicates the observed scattering intensity. While each of these data perturbations has been studied separately, a combined calculation is important to indicate the validity of separate treatments. Solution-grown hexatriacontane, C36 H74, a long-chain hydrocarbon with the long axis (c=95.14Å) parallel to the electron beam direction exhibits significant dynamical and bend effects. It is thus a particularly difficult structure to analyse from hkO electron diffraction data. Multislice dynamical calculations for a curved crystal lattice of this material are considered.

A thermal and X-ray investigation of scarbroite

1960 ◽  
Vol 32 (248) ◽  
pp. 353-362 ◽  
Author(s):  
W. J. Duffin ◽  
J. Goodyear
Keyword(s):  
Electron Diffraction ◽  
Chemical Analysis ◽  
Diffraction Data ◽  
Room Temperature ◽  
Layer Structure ◽  
Electron Diffraction Data ◽  
X Ray ◽  
Fine Grained ◽  
The North

SummaryScarbroite, a fine-grained but compact deposit obtained from fissures in the sandstone on the north Yorkshire coast, is shown by chemical analysis to have an idealized formula Al2(CO3)3·12Al(OH)3. X-ray and electron diffraction data indicate a triclinic cell with a 9·94 Å., b 14·88 Å., c 26·47 Å., α 98·7°, β 96·5°, and γ 89·0°. A layer structure consisting of gibbsite-type sheets of Al(OH)3 and sheets of Al2(CO3)3 is proposed. The structure is stable from room temperature to about 125° C.

A complex pseudo-decagonal quasicrystal approximant, Al37(Co,Ni)15.5, solved by rotation electron diffraction

2014 ◽  
Vol 47 (1) ◽  
pp. 215-221 ◽  
Author(s):  
Devinder Singh ◽  
Yifeng Yun ◽  
Wei Wan ◽  
Benjamin Grushko ◽  
Xiaodong Zou ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Basic Structure ◽  
Electron Diffraction Data ◽  
Dimensional Electron ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns

Electron diffraction is a complementary technique to single-crystal X-ray diffraction and powder X-ray diffraction for structure solution of unknown crystals. Crystals too small to be studied by single-crystal X-ray diffraction or too complex to be solved by powder X-ray diffraction can be studied by electron diffraction. The main drawbacks of electron diffraction have been the difficulties in collecting complete three-dimensional electron diffraction data by conventional electron diffraction methods and the very time-consuming data collection. In addition, the intensities of electron diffraction suffer from dynamical scattering. Recently, a new electron diffraction method, rotation electron diffraction (RED), was developed, which can overcome the drawbacks and reduce dynamical effects. A complete three-dimensional electron diffraction data set can be collected from a sub-micrometre-sized single crystal in less than 2 h. Here the RED method is applied forab initiostructure determination of an unknown complex intermetallic phase, the pseudo-decagonal (PD) quasicrystal approximant Al37.0(Co,Ni)15.5, denoted as PD2. RED shows that the crystal is F-centered, witha= 46.4,b= 64.6,c= 8.2 Å. However, as with other approximants in the PD series, the reflections with oddlindices are much weaker than those withleven, so it was decided to first solve the PD2 structure in the smaller, primitive unit cell. The basic structure of PD2 with unit-cell parametersa= 23.2,b= 32.3,c= 4.1 Å and space groupPnmmhas been solved in the present study. The structure withc= 8.2 Å will be taken up in the near future. The basic structure contains 55 unique atoms (17 Co/Ni and 38 Al) and is one of the most complex structures solved by electron diffraction. PD2 is built of characteristic 2 nm wheel clusters with fivefold rotational symmetry, which agrees with results from high-resolution electron microscopy images. Simulated electron diffraction patterns for the structure model are in good agreement with the experimental electron diffraction patterns obtained by RED.

A Search/Match Procedure for Electron Diffraction Data Based on Pattern Matching in Binary Bit Maps

1986 ◽  
Vol 1 (3) ◽  
pp. 226-234 ◽  
Author(s):  
Martin J. Carr ◽  
William F. Chambers ◽  
David Melgaard
Keyword(s):  
Electron Diffraction ◽  
Diffraction Analysis ◽  
Pattern Matching ◽  
Diffraction Data ◽  
Reference Data ◽  
Search Algorithm ◽  
Energy Dispersive ◽  
Electron Diffraction Data ◽  
Electron Diffraction Analysis ◽  
X Ray

AbstractA unique file structure and search algorithm have been developed for the purpose of obtaining matches between experimental electron diffraction and qualitative energy dispersive X-ray compositional data from an unknown crystalline phase and the reference data in the JCPDS Powder Diffraction File. The reference data for over 32,000 inorganic compounds from sets 1–33 were compressed and stored in binary format as bit pattern maps. The entire data set and searching programs require less than 4 Mbyte and retain the precision appropriate for electron diffraction analysis. The search algorithm, written in both RT-11 FORTRAN and Flextran, is based on pattern matching between bit maps obtained for the unknown and reference compounds for both composition and diffraction data. Special attention is given to double diffraction effects commonly encountered in electron diffraction analysis. The programs run on an interactive basis on a microcomputer dedicated to the X-ray energy dispersive spectrometer on an analytical electron microscope. A typical search takes about 15 seconds to run and extracts about 10–15 different compounds.

scholarly journals A Medipix quantum area detector allows rotation electron diffraction data collection from submicrometre three-dimensional protein crystals

2013 ◽  
Vol 69 (7) ◽  
pp. 1223-1230 ◽  
Author(s):  
Igor Nederlof ◽  
Eric van Genderen ◽  
Yao-Wang Li ◽  
Jan Pieter Abrahams
Keyword(s):  
Electron Diffraction ◽  
Data Collection ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Protein Crystal ◽  
Protein Crystals ◽  
Electron Diffraction Data ◽  
Single Shot ◽  
X Ray ◽  
Area Detector

When protein crystals are submicrometre-sized, X-ray radiation damage precludes conventional diffraction data collection. For crystals that are of the order of 100 nm in size, at best only single-shot diffraction patterns can be collected and rotation data collection has not been possible, irrespective of the diffraction technique used. Here, it is shown that at a very low electron dose (at most 0.1 e− Å−2), a Medipix2 quantum area detector is sufficiently sensitive to allow the collection of a 30-frame rotation series of 200 keV electron-diffraction data from a single ∼100 nm thick protein crystal. A highly parallel 200 keV electron beam (λ = 0.025 Å) allowed observation of the curvature of the Ewald sphere at low resolution, indicating a combined mosaic spread/beam divergence of at most 0.4°. This result shows that volumes of crystal with low mosaicity can be pinpointed in electron diffraction. It is also shown that strategies and data-analysis software (MOSFLMandSCALA) from X-ray protein crystallography can be used in principle for analysing electron-diffraction data from three-dimensional nanocrystals of proteins.

On the quality of the continuous rotation electron diffraction data for accurate atomic structure determination of inorganic compounds

2018 ◽  
Vol 51 (4) ◽  
pp. 1094-1101 ◽  
Author(s):  
Yunchen Wang ◽  
Taimin Yang ◽  
Hongyi Xu ◽  
Xiaodong Zou ◽  
Wei Wan
Keyword(s):  
Electron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Structural Models ◽  
Electron Diffraction Data ◽  
Data Sets ◽  
X Ray Diffraction ◽  
X Ray ◽  
Continuous Rotation

The continuous rotation electron diffraction (cRED) method has the capability of providing fast three-dimensional electron diffraction data collection on existing and future transmission electron microscopes; unknown structures could be potentially solved and refined using cRED data collected from nano- and submicrometre-sized crystals. However, structure refinements of cRED data using SHELXL often lead to relatively high R1 values when compared with those refined against single-crystal X-ray diffraction data. It is therefore necessary to analyse the quality of the structural models refined against cRED data. In this work, multiple cRED data sets collected from different crystals of an oxofluoride (FeSeO3F) and a zeolite (ZSM-5) with known structures are used to assess the data consistency and quality and, more importantly, the accuracy of the structural models refined against these data sets. An evaluation of the precision and consistency of the cRED data by examination of the statistics obtained from the data processing software DIALS is presented. It is shown that, despite the high R1 values caused by dynamical scattering and other factors, the refined atomic positions obtained from the cRED data collected for different crystals are consistent with those of the reference models refined against single-crystal X-ray diffraction data. The results serve as a reference for the quality of the cRED data and the achievable accuracy of the structural parameters.

Non-planar structures of Et3N and Pri3N: a contradiction between the X-ray, and NMR and electron diffraction data for Pri3N

1998 ◽  
pp. 781-782 ◽  
Author(s):  
Roland Boese ◽  
Dieter Bläser ◽  
Mikhail Y. Antipin ◽  
Roland Boese ◽  
Mikhail Y. Antipin ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Electron Diffraction Data ◽  
X Ray ◽  
Planar Structures

scholarly journals Evaluation of the Structure of Amorphous Tungsten Oxide W28O72 by the Combination of Electron-, X-Ray- and Neutron-Diffraction (Three-Beam Experiment)

2006 ◽  
Vol 61 (3-4) ◽  
pp. 189-196 ◽  
Author(s):  
Jürgen Ankele ◽  
Joachim Mayer ◽  
Peter Lamparter ◽  
Siegfried Steeb
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Data ◽  
Structural Model ◽  
Pair Correlation ◽  
Electron Diffraction Data ◽  
X Ray ◽  
Structure Factors ◽  
Beam Experiment ◽  
Reverse Monte Carlo Simulation ◽  
Sputter Deposited

From the combination of quantitative electron-diffraction data with X-ray- and neutron-diffraction data (so-called three-beam experiment) the partial structure factors and pair correlation functions of amorphous sputter deposited W28O72 were determined. On the basis of the experimental atomic distances and coordination numbers, and by comparison with crystalline WO3, a structural model was developed, which consists of twisted WO6 octahedra. Reverse Monte Carlo simulation in accordance with the experimental data was performed to verify the results

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