scholarly journals Accurate structure refinement from 3D electron diffraction data

2014 ◽  
Vol 70 (a1) ◽  
pp. C374-C374
Author(s):  
Lukáš Palatinus ◽  
Cinthia Corrêa ◽  
Gwladys Mouillard ◽  
Philippe Boullay ◽  
Damien Jacob
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Three Dimensional ◽  
Diffraction Theory ◽  
Electron Diffraction Data ◽  
Dynamical Structure ◽  
Present Contribution ◽  
Figures Of Merit ◽  
Precession Electron Diffraction

Structure determination from electron diffraction data has seen an enormous progress over the past few years. At present, complex structures with hundreds of atoms in the unit cell can be solved from electron diffraction using the concept of electron diffraction tomography (EDT), possibly combined with precession electron diffraction (PED) [1]. Unfortunately, the initial model is typically optimized using the kinematical approximation to calculate model diffracted intensities. This approximation is quite inaccurate for electron diffraction and leads to high figures of merit and inaccurate results with unrealistically low standard uncertainties. The obvious remedy to the problem is the use of dynamical diffraction theory to calculate the model intensities in structure refinement. This technique has been known and used before, but it has not become very popular, because good fits could be obtained only for sufficiently perfect and sufficiently thin crystals. It has been shown recently on several zone-axis patterns [2] that the quality of the refinement can be improved by using precession electron diffraction. In the present contribution we demonstrate that the same approach can be successfully used to refine crystal structures against non-oriented patterns acquired by EDT combined with PED (PEDT in short). Because the PEDT technique provides three-dimensional diffraction information, it can be used for a complete structure refinement. Several test examples demonstrate that the dynamical structure refinement yields better figures of merit and more accurate results than the refinement using kinematical approximation.

Structure refinement using precession electron diffraction tomography and dynamical diffraction: theory and implementation

2015 ◽  
Vol 71 (2) ◽  
pp. 235-244 ◽  
Author(s):  
Lukáš Palatinus ◽  
Václav Petříček ◽  
Cinthia Antunes Corrêa
Keyword(s):  
Electron Diffraction ◽  
Rotation Axis ◽  
Structure Refinement ◽  
Three Dimensional ◽  
Electron Diffraction Data ◽  
Diffraction Tomography ◽  
Three Dimensional Model ◽  
Data Set ◽  
Dynamical Diffraction ◽  
Precession Electron Diffraction

Accurate structure refinement from electron-diffraction data is not possible without taking the dynamical-diffraction effects into account. A complete three-dimensional model of the structure can be obtained only from a sufficiently complete three-dimensional data set. In this work a method is presented for crystal structure refinement from the data obtained by electron diffraction tomography, possibly combined with precession electron diffraction. The principle of the method is identical to that used in X-ray crystallography: data are collected in a series of small tilt steps around a rotation axis, then intensities are integrated and the structure is optimized by least-squares refinement against the integrated intensities. In the dynamical theory of diffraction, the reflection intensities exhibit a complicated relationship to the orientation and thickness of the crystal as well as to structure factors of other reflections. This complication requires the introduction of several special parameters in the procedure. The method was implemented in the freely available crystallographic computing systemJana2006.

Structure refinement from precession electron diffraction data

2013 ◽  
Vol 69 (2) ◽  
pp. 171-188 ◽  
Author(s):  
Lukáš Palatinus ◽  
Damien Jacob ◽  
Priscille Cuvillier ◽  
Mariana Klementová ◽  
Wharton Sinkler ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Electron Diffraction Data ◽  
Precession Electron Diffraction

scholarly journals Structure refinement against precession electron diffraction data

2012 ◽  
Vol 68 (a1) ◽  
pp. s60-s60
Author(s):  
L. Palatinus ◽  
M. Klementova ◽  
D. Jacob ◽  
P. Cuvillier ◽  
W. Sinkler ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Electron Diffraction Data ◽  
Precession Electron Diffraction

Crystal structure redetermination of ε-Ni3Si2 from a single nanowire by dynamical refinement of precession electron diffraction data

2016 ◽  
Vol 672 ◽  
pp. 505-509 ◽  
Author(s):  
Cinthia Antunes Corrêa ◽  
Mariana Klementová ◽  
Vladislav Dřínek ◽  
Jaromír Kopeček ◽  
Lukáš Palatinus
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Electron Diffraction Data ◽  
Single Nanowire ◽  
Precession Electron Diffraction

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.

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