Essential features of the polytypic charoite-96 structure compared to charoite-90

2011 ◽  
Vol 75 (6) ◽  
pp. 2833-2846 ◽  
Author(s):  
I. V. Rozhdestvenskaya ◽  
E. Mugnaioli ◽  
M. Czank ◽  
W. Depmeier ◽  
U. Kolb ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Ab Initio ◽  
Direct Methods ◽  
Diffraction Tomography ◽  
Space Group ◽  
Sakha Republic ◽  
Alkaline Intrusion ◽  
Different Types

AbstractCharoite, ideally (K,Sr,Ba,Mn)15–16(Ca,Na)32[(Si70(O,OH)180)](OH,F)4·nH20, is a rock-forming mineral from the Murun massif in Yakutia, Sakha Republic, Siberia, Russia, where it occurs in a unique alkaline intrusion. Charoite occurs as four different polytypes, which are commonly intergrown in nanocrystallme fibres. We report the structure of charoite-96 (a = 32.11(6), b = 19.77(4), c = 7.23(1) Å, β = 95.85(9)°, V = 4565(24) Å3, space group P21/m), which was solved ab initio by direct methods on the basis of 2676 unique electron diffraction reflections collected by automated diffraction tomography and refined to R1/wR2 = 0.34/0.37. The structure of charoite-96 is related to that of the charoite-90, which was also solved recently. Both structures are composed of three different types of dreier silicate chains running along [001] and separated by ribbons of edge-sharing Ca- and Na-centred octahedra. In the structure of charoite-96, adjacent blocks formed by three different silicate chains and stacked along the x axis, are shifted by a translation of 1/2 c. The shifts involve a hybrid dreier quadruple chain, [Si17O43]18– and a double dreier chain, [Si6O17]10–. In charoite-90 adjacent blocks are stacked without shifts.

Automated diffraction tomography combined with electron precession: a new tool for ab initio nanostructure analysis

2009 ◽  
Vol 1184 ◽  
Author(s):  
Ute Kolb ◽  
Tatiana Gorelik ◽  
Enrico Mugnaioli
Keyword(s):  
Electron Diffraction ◽  
Ab Initio ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Direct Methods ◽  
Electron Diffraction Data ◽  
Diffraction Tomography ◽  
Diffraction Mode ◽  
Structure Solution

AbstractThree-dimensional electron diffraction data was collected with our recently developed module for automated diffraction tomography and used to solve inorganic as well as organic crystal structures ab initio. The diffraction data, which covers nearly the full relevant reciprocal space, was collected in the standard nano electron diffraction mode as well as in combination with the precession technique and was subsequently processed with a newly developed automated diffraction analysis and processing software package. Non-precessed data turned out to be sufficient for ab initio structure solution by direct methods for simple crystal structures only, while precessed data allowed structure solution and refinement in all of the studied cases.

Electron Diffraction Reinvestigation of CdCr2Se4 and ZnCr2-xVxSe4 Spinel Structures

2013 ◽  
Vol 203-204 ◽  
pp. 262-265
Author(s):  
Maciej Zubko ◽  
Joanna Wspaniała ◽  
Danuta Stróż ◽  
Enrico Mugnaioli
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Single Crystals ◽  
Reciprocal Space ◽  
Diffraction Tomography ◽  
Cubic Symmetry ◽  
Space Group ◽  
Tilt Series ◽  
Tomography Method ◽  
Spinel Structures

Crystal structure of two spinel single crystals CdCr2Se4 and ZnCr2-xVxSe4 have been reinvestigated using automated electron diffraction tomography method with beam precession. 3D reciprocal space have been reconstructed base on recorded tilt series. For both samples crystal structure was refined and the cubic symmetry with space group Fd-3m was confirmed. No additional electron potential has been located beside occupied atom sites.

Ab initiostructure determination and quantitative disorder analysis on nanoparticles by electron diffraction tomography

2018 ◽  
Vol 74 (2) ◽  
pp. 93-101 ◽  
Author(s):  
Yaşar Krysiak ◽  
Bastian Barton ◽  
Bernd Marler ◽  
Reinhard B. Neder ◽  
Ute Kolb
Keyword(s):  
Electron Diffraction ◽  
Direct Methods ◽  
Functional Materials ◽  
Structural Features ◽  
Zeolite Beta ◽  
Electron Diffraction Data ◽  
Diffraction Tomography ◽  
Separation Processes ◽  
Data Set

Nanoscaled porous materials such as zeolites have attracted substantial attention in industry due to their catalytic activity, and their performance in sorption and separation processes. In order to understand the properties of such materials, current research focuses increasingly on the determination of structural features beyond the averaged crystal structure. Small particle sizes, various types of disorder and intergrown structures render the description of structures at atomic level by standard crystallographic methods difficult. This paper reports the characterization of a strongly disordered zeolite structure, using a combination of electron exit-wave reconstruction, automated diffraction tomography (ADT), crystal disorder modelling and electron diffraction simulations. Zeolite beta was chosen for a proof-of-principle study of the techniques, because it consists of two different intergrown polymorphs that are built from identical layer types but with different stacking sequences. Imaging of the projected inner Coulomb potential of zeolite beta crystals shows the intergrowth of the polymorphs BEA and BEB. The structures of BEA as well as BEB could be extracted from one single ADT data set using direct methods. A ratio for BEA/BEB = 48:52 was determined by comparison of the reconstructed reciprocal space based on ADT data with simulated electron diffraction data for virtual nanocrystals, built with different ratios of BEA/BEB. In this way, it is demonstrated that this smart interplay of the above-mentioned techniques allows the elaboration of the real structures of functional materials in detail – even if they possess a severely disordered structure.

The Application of Ab Initio Direct Methods with Electron Diffraction for Solving Zeolite Structures

2001 ◽  
Vol 7 (S2) ◽  
pp. 1068-1069
Author(s):  
Wharton Sinkler
Keyword(s):  
Electron Diffraction ◽  
Ab Initio ◽  
Direct Methods ◽  
Ccd Camera ◽  
Spot Size ◽  
Combined Approach ◽  
Inorganic Crystal ◽  
Minimum Relative Entropy ◽  
Kinematical Data ◽  
Made In

Recently a number of reports have been made in which direct methods (DM) were used to solve bulk inorganic crystal structures with electron diffraction (ED) data, either ab initio or in a combined approach using phase information from images. This paper reports ab initio application of DM to experimental ED data from the zeolite mordenite. Data from mordenite [001] were taken using a JEOL 3010 TEM at 300 kV. For collecting data, a small condenser and spot size were used to obtain a defocused probe 50 nm in size positioned over the edge of a thin area. Patterns were recorded with a CCD camera. Fig. 1 compares experiment with modeled kinematical data based on a published structure. Phase determination by DM was performed with the minimum relative entropy approach. As a test, ab initio DM was performed on modeled kinematical data.The result, shown in Fig. 2, is not distinguishable from a picture of the projected potential.

Fast electron diffraction tomography

2015 ◽  
Vol 48 (3) ◽  
pp. 718-727 ◽  
Author(s):  
Mauro Gemmi ◽  
Maria G. I. La Placa ◽  
Athanassios S. Galanis ◽  
Edgar F. Rauch ◽  
Stavros Nicolopoulos
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Direct Methods ◽  
Diffraction Tomography ◽  
Automatic Data ◽  
Cell Parameters ◽  
Continuous Rotation ◽  
Fully Automatic ◽  
Data Collections ◽  
Tomography Data

A fast and fully automatic procedure for collecting electron diffraction tomography data is presented. In the case of a very stable goniometer it is demonstrated how, by variation of the tilting speed and the CCD detector parameters, it is possible to obtain fully automatic precession-assisted electron diffraction tomography data collections, rotation electron diffraction tomography data collections or new integrated electron diffraction tomography data collections, in which the missing wedge of the reciprocal space between the patterns is recorded by longer exposures during the crystal tilt. It is shown how automatic data collection of limited tilt range can be used to determine the unit-cell parameters, while data of larger tilt range are suitable to solve the crystal structureabinitiowith direct methods. The crystal structure of monoclinic MgMoO4has been solved in this way as a test structure. In the case where the goniometer is not stable enough to guarantee a steady position of the crystal over large tilt ranges, an automatic method for tracking the crystal during continuous rotation of the sample is proposed.

scholarly journals Ab Initio Structure Determination of Cu2–xTe Plasmonic Nanocrystals by Precession-Assisted Electron Diffraction Tomography and HAADF-STEM Imaging

2018 ◽  
Vol 57 (16) ◽  
pp. 10241-10248 ◽  
Author(s):  
Enrico Mugnaioli ◽  
Mauro Gemmi ◽  
Renyong Tu ◽  
Jeremy David ◽  
Giovanni Bertoni ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Ab Initio ◽  
Structure Determination ◽  
Diffraction Tomography ◽  
Ab Initio Structure

scholarly journals The structure of charoite, (K,Sr,Ba,Mn)15–16(Ca,Na)32[(Si70(O,OH)180)](OH,F)4.0.nH2O, solved by conventional and automated electron diffraction

2010 ◽  
Vol 74 (1) ◽  
pp. 159-177 ◽  
Author(s):  
I. Rozhdestvenskaya ◽  
E. Mugnaioli ◽  
M. Czank ◽  
W. Depmeier ◽  
U. Kolb ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Direct Methods ◽  
Diffraction Tomography ◽  
Chemical Formula ◽  
Crystal Chemical Formula ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Precession Electron Diffraction ◽  
Cation Sites

AbstractCharoite, ideally (K,Sr,Ba,Mn)15–16(Ca,Na)32[(Si70(O,OH)180)](OH,F)4.0·nH2O, a rare mineral from the Murun massif in Yakutiya, Russia, was studied using high-resolution transmission electron microscopy, selected-area electron diffraction, X-ray spectroscopy, precession electron diffraction and the newly developed technique of automated electron-diffraction tomography. The structure of charoite (a = 31.96(6) Å, b = 19.64(4) Å, c = 7.09(1) Å, β = 90.0(1)°, V = 4450(24) Å3, space group P21/m) was solved ab initio by direct methods from 2878 unique observed reflections and refined to R1/wR2 = 0.17/0.21. The structure can be visualized as being composed of three different dreier silicate chains: a double dreier chain, [Si6O17]10–; a tubular loop-branched dreier triple chain, [Si12O30]12–; and a tubular hybrid dreier quadruple chain, [Si17O43]18–. The silicate chains occur between ribbons of edge-sharing Ca and Na-octahedra. The chains of tetrahedra and the ribbons of octahedra extend parallel to the z axis. K+, Ba2+, Sr2+, Mn2+ and H2O molecules lie inside tubes and channels of the structure. On the basis of microprobe analyses and occupancy refinement of the cation sites, the crystal chemical formula of this charoite can be written as (Z = 1): (K13.88Sr1.0Ba0.32Mn0.36)Σ15.56(Ca25.64Na6.36)Σ32 [(Si6O11(O,OH)6)2(Si12O18(O,OH)12)2(Si17O25(O,OH)18)2](OH,F)4.0·3.18H2O.

Multislice calculations for quasi-periodic and non-periodic objects

1990 ◽  
Vol 48 (4) ◽  
pp. 138-139
Author(s):  
R. Herrera ◽  
A. Gómez
Keyword(s):  
Electron Diffraction ◽  
Computer Simulations ◽  
Periodic Table ◽  
Amorphous Materials ◽  
Space Group ◽  
Essential Step ◽  
Shape Effects ◽  
Atomic Scattering ◽  
Diffraction Patterns ◽  
Periodic Continuation

Computer simulations of electron diffraction patterns and images are an essential step in the process of structure and/or defect elucidation. So far most programs are designed to deal specifically with crystals, requiring frequently the space group as imput parameter. In such programs the deviations from perfect periodicity are dealt with by means of “periodic continuation”.However, for many applications involving amorphous materials, quasiperiodic materials or simply crystals with defects (including finite shape effects) it is convenient to have an algorithm capable of handling non-periodicity. Our program “HeGo” is an implementation of the well known multislice equations in which no periodicity assumption is made whatsoever. The salient features of our implementation are: 1) We made Gaussian fits to the atomic scattering factors for electrons covering the whole periodic table and the ranges [0-2]Å−1 and [2-6]Å−1.

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