Electron Crystallography-Structure Determination by Combining HREM, Crystallographic Image Processing and Electron Diffraction

2001 ◽  
pp. 191-222 ◽  
Author(s):  
Xiaodong Zou ◽  
Thomas E. Weirich ◽  
Sven Hovmöller
Keyword(s):  
Image Processing ◽  
Electron Diffraction ◽  
Structure Determination ◽  
Electron Crystallography

scholarly journals Single Crystal 3D Rotation Electron Diffraction from Nano-sized Crystals

2014 ◽  
Vol 70 (a1) ◽  
pp. C366-C366
Author(s):  
Xiaodong Zou
Keyword(s):  
Electron Diffraction ◽  
Data Collection ◽  
Data Processing ◽  
Single Crystal ◽  
Diffraction Data ◽  
Structure Determination ◽  
Reciprocal Lattice ◽  
Electron Diffraction Data ◽  
Electron Crystallography ◽  
Structure Solution

Electron crystallography is an important technique for structure analysis of nano-sized materials. Crystals too small or too complicated to be studied by X-ray diffraction can be investigated by electron crystallography. However, conventional TEM methods requires high TEM skills and strong crystallographic knowledge, which many synthetic materials scientists and chemists do not have. We recently developed the software-based Rotation Electron Diffraction (RED) method for automated collection and processing of 3D electron diffraction data. Complete single crystal 3D electron diffraction data can be collected from nano- and micron-sized crystals in less than one hour by combining electron beam tilt and goniometer tilt, which are controlled by the RED – data collection software.3 The unit cell, possible space groups and electron diffraction intensities can be obtained from the RED data using the RED data processing software. The figure below illustrates the data collection and data processing of a zeolite silicalite-1 by RED. 1427 ED frames were collected in less than 1 hour from a crystal of 800 x 400 x 200 nm in size. A 3D reciprocal lattice of silicalite-1 was reconstructed from the ED frames, from which the unit cell parameters and space group were determined (P21/n, a=20.02Å, b=20.25Å, c=13.35Å, alfa=90.130, beta=90.740, gamma=90.030. It was possible to cut the 3D reciprocal lattice perpendicular to any directions and study the reflection conditions. The reflection intensities could be extracted. The structure of the calcined silicalite-1 could be solved from the RED data by routine direct methods using SHELX-97. All 78 unique Si and O atoms could be located and refined to an accuracy better than 0.08 Å. The RED method has been applied for structure solution of a wide range of crystals and shown to be very powerful and efficient. Now a structure determination can be achieved within a few hours, from the data collection to structure solution. We will present several examples including unknown inorganic compounds, metal-organic frameworks and organic structures solved from the RED data. Different parameters that affect the RED data quality and thus the structure determination will be discussed. The methods are general and can be applied to any crystalline materials.

scholarly journals A Method to Characterize and Correct Elliptical Distortion in Electron Diffraction Patterns

2008 ◽  
Vol 16 (3) ◽  
pp. 36-41
Author(s):  
Vincent D.-H. Hou ◽  
Du Li
Keyword(s):  
Image Processing ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Electron Diffraction Data ◽  
Objective Lens ◽  
Lens System ◽  
Electron Crystallography ◽  
Diffraction Ring ◽  
Diffraction Patterns ◽  
Instrument Level

One of the main obstacles to performing electron crystallography analysis in a TEM is that the acquired electron diffraction data often exhibits some form of distortion introduced by the lens system. Recognizing this problem, Capitani et al. has proposed a method to detect such distortion, which is primarily elliptical, by using a single crystal standard. Once such elliptical distortion is characterized, electron diffraction data acquired later can then be corrected by means of image processing. However, it may be desirable to correct such distortion at the instrument level. In this article, a different approach to measuring diffraction elliptical distortion is proposed by characterizing diffraction ring patterns and it is demonstrated that by varying the objective lens stigmation settings, it is possible to eliminate this elliptical distortion completely.

Crystal Structure Determination of Glycerol-Containing Lipids from Electron Diffraction Data. Use of Analog Compounds Based upon Configurational Isomers of Cyclopentane-1, 2, 3-TRIOL

1977 ◽  
Vol 35 ◽  
pp. 24-25
Author(s):  
Douglas L. Dorset ◽  
Anthony J. Hancock
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Crystal Surface ◽  
Coherent Scattering ◽  
Crystal Structure Determination ◽  
Electron Diffraction Data ◽  
Polar Group ◽  
Axis Orientation

Lipids containing long polymethylene chains were among the first compounds subjected to electron diffraction structure analysis. It was only recently realized, however, that various distortions of thin lipid microcrystal plates, e.g. bends, polar group and methyl end plane disorders, etc. (1-3), restrict coherent scattering to the methylene subcell alone, particularly if undistorted molecular layers have well-defined end planes. Thus, ab initio crystal structure determination on a given single uncharacterized natural lipid using electron diffraction data can only hope to identify the subcell packing and the chain axis orientation with respect to the crystal surface. In lipids based on glycerol, for example, conformations of long chains and polar groups about the C-C bonds of this moiety still would remain unknown.One possible means of surmounting this difficulty is to investigate structural analogs of the material of interest in conjunction with the natural compound itself. Suitable analogs to the glycerol lipids are compounds based on the three configurational isomers of cyclopentane-1,2,3-triol shown in Fig. 1, in which three rotameric forms of the natural glycerol derivatives are fixed by the ring structure (4-7).

Structure determination by electron diffraction and HREM of the incommensurate modulated phase BaxCuO2 (0.67≤x≤0.70)

1999 ◽  
Vol 328 (1-2) ◽  
pp. 89-103 ◽  
Author(s):  
A Migliori ◽  
M Gemmi ◽  
G Calestani ◽  
D Belletti ◽  
F.C Matacotta ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Structure Determination ◽  
Modulated Phase

scholarly journals A nanocrystalline monoclinic CaCO3precursor of metastable aragonite

2018 ◽  
Vol 4 (12) ◽  
pp. eaau6178 ◽  
Author(s):  
Péter Németh ◽  
Enrico Mugnaioli ◽  
Mauro Gemmi ◽  
György Czuppon ◽  
Attila Demény ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Structure Determination ◽  
Diffuse Scattering ◽  
Diffraction Tomography ◽  
Synthetic Material ◽  
Near Surface ◽  
Surface Conditions ◽  
Terrestrial Sediments ◽  
Living Organisms ◽  
New Phase

Despite its thermodynamical metastability at near-surface conditions, aragonite is widespread in marine and terrestrial sediments. It abundantly forms in living organisms, and its abiotic formation is favored in waters of a Mg2+/Ca2+ratio > 1.5. Here, we provide crystallographic evidence of a nanocrystalline CaCO3polymorph, which precipitates before aragonite in a cave. The new phase, which we term monoclinic aragonite (mAra), is crystallographically related to ordinary, orthorhombic aragonite. Electron diffraction tomography combined with structure determination demonstrates that mAra has a layered aragonite structure, in which some carbonates can be replaced by hydroxyls and up to 10 atomic % of Mg can be incorporated. The diagnostic electron diffraction features of mAra are diffuse scattering and satellite reflections along aragonite {110}. Similar features have previously been reported—although unrecognized—from biogenic aragonite formed in stromatolites, mollusks, and cyanobacteria as well as from synthetic material. We propose that mAra is a widespread crystalline CaCO3that plays a hitherto unrecognized key role in metastable aragonite formation.

Structure determination of modulated structures by powder X-ray diffraction and electron diffraction

2016 ◽  
Vol 3 (11) ◽  
pp. 1351-1362 ◽  
Author(s):  
Zhengyang Zhou ◽  
Lukáš Palatinus ◽  
Junliang Sun
Keyword(s):  
Electron Diffraction ◽  
Structure Determination ◽  
X Ray Diffraction ◽  
X Ray ◽  
Modulated Structures ◽  
Conventional Methods

The combination of PXRD and ED is applied to determine modulated structures which resist solution by more conventional methods.

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