Structure solution of the new titanate Li4Ti8Ni3O21 using precession electron diffraction

2009 ◽  
Vol 66 (1) ◽  
pp. 60-68 ◽  
Author(s):  
Mauro Gemmi ◽  
Holger Klein ◽  
Amelie Rageau ◽  
Pierre Strobel ◽  
Federic Le Cras
Keyword(s):  
Electron Diffraction ◽  
Three Dimensional ◽  
Direct Methods ◽  
Electron Diffraction Experiment ◽  
Cation Site ◽  
Synchrotron Powder Diffraction ◽  
Edge Sharing Octahedra ◽  
Structure Solution ◽  
Precession Electron Diffraction ◽  
Trigonal Phase

A sample having stoichiometry Li[Ti1.5Ni0.5]O4 has been synthesized to obtain a spinel structure. The resulting crystalline powder revealed a multiphase nature with spinel as the minor phase. The main phase is a new trigonal phase having a = 5.05910 (1), c = 32.5371 (1) Å. The structure has been solved by direct methods working on a three-dimensional set of intensities obtained from a precession electron-diffraction experiment, and refined on synchrotron powder diffraction data in the space group P\bar 3c1. The model consists of hexagonal layers of edge-sharing octahedra occupied either by the heavy cations Ti and Ni, or preferentially by Li. On the basis of cation-site occupancies the stoichiometry becomes Li4Ti8Ni3O21, which is compatible with the microanalysis results.

scholarly journals UsingFOCUSto solve zeolite structures from three-dimensional electron diffraction data

2013 ◽  
Vol 46 (4) ◽  
pp. 1017-1023 ◽  
Author(s):  
Stef Smeets ◽  
Lynne B. McCusker ◽  
Christian Baerlocher ◽  
Enrico Mugnaioli ◽  
Ute Kolb
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Direct Methods ◽  
Electron Diffraction Data ◽  
Chemical Information ◽  
Data Sets ◽  
Dimensional Electron ◽  
Specific Chemical ◽  
Structure Solution

The programFOCUS[Grosse-Kunstleve, McCusker & Baerlocher (1997).J. Appl. Cryst.30, 985–995] was originally developed to solve zeolite structures from X-ray powder diffraction data. It uses zeolite-specific chemical information (three-dimensional 4-connected framework structure with known bond distances and angles) to supplement the diffraction data. In this way, it is possible to compensate, at least in part, for the ambiguity of the reflection intensities resulting from reflection overlap, and the program has proven to be quite successful. Recently, advances in electron microscopy have led to the development of automated diffraction tomography (ADT) and rotation electron diffraction (RED) techniques for collecting three-dimensional electron diffraction data on very small crystallites. Reasoning that such data are also less than ideal (dynamical scattering, low completeness, beam damage) and that this can lead to failure of structure solution by conventional direct methods for very complex zeolite frameworks,FOCUSwas modified to accommodate electron diffraction data. The modified program was applied successfully to five different data sets (four ADT and one RED) collected on zeolites of different complexities. One of these could not be solved completely by direct methods but emerged easily in theFOCUStrials.

scholarly journals Structural study of decrespignyite-(Y), a complex yttrium rare earth copper carbonate chloride, by three-dimensional electron and synchrotron powder diffraction

2020 ◽  
Vol 32 (5) ◽  
pp. 545-555
Author(s):  
Jordi Rius ◽  
Fernando Colombo ◽  
Oriol Vallcorba ◽  
Xavier Torrelles ◽  
Mauro Gemmi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Three Dimensional ◽  
South Australia ◽  
Direct Methods ◽  
Unit Cell ◽  
Synchrotron Powder Diffraction ◽  
Structure Solution ◽  
Hexanuclear Clusters ◽  
Metal Layers

Abstract. The crystal structure of the mineral decrespignyite-(Y) from the Paratoo copper mine (South Australia) has been obtained by applying δ recycling direct methods to 3D electron diffraction (ED) data followed by Rietveld refinements of synchrotron data. The unit cell is a= 8.5462(2), c= 22.731(2) Å and V= 1437.8(2) Å3, and the chemical formula for Z=1 is (Y10.35REE1.43Ca0.52Cu5.31)Σ17.61(CO3)14Cl2.21(OH)16.79⋅18.35H2O (REE: rare earth elements). The ED data are compatible with the trigonal P3‾m1 space group (no. 164) used for the structure solution (due to the disorder affecting part of the structure, the possibility of a monoclinic unit cell cannot completely be ruled out). The structure shows metal layers perpendicular to [001], with six independent positions for Y, REE and Cu (sites M1 to M4 are full, and sites M5 and M6 are partially vacant), and two other sites, Cu1 and Cu2, partially occupied by Cu. One characteristic of decrespignyite is the existence of hexanuclear (octahedral) oxo-hydroxo yttrium clusters [Y6(μ6-O)(μ3-OH)8O24] (site M1) with the 24 bridging O atoms belonging to two sets of symmetry-independent (CO3)2− ions, with the first set (2×) along a ternary axis giving rise to a layer of hexanuclear clusters and the second set (6×) tilted and connecting the hexanuclear clusters with hetero-tetranuclear ones hosting Cu, Y and REE (M2 and M3 sites). The rest of the crystal structure consists of two consecutive M3 + M4 layers containing the partially occupied M5, M6, and Cu2 sites and additional carbonate anions in between. The resulting structure model is compatible with the chemical analysis of the type material which is poorer in Cu and richer in (REE, Y) than the above-described material.

Atomic structure solution of the complex quasicrystal approximant Al77Rh15Ru8from electron diffraction data

2014 ◽  
Vol 70 (6) ◽  
pp. 999-1005 ◽  
Author(s):  
Shmuel Samuha ◽  
Enrico Mugnaioli ◽  
Benjamin Grushko ◽  
Ute Kolb ◽  
Louisa Meshi
Keyword(s):  
Electron Diffraction ◽  
Structural Model ◽  
Direct Methods ◽  
High Resolution Electron Microscopy ◽  
Single Type ◽  
Electron Diffraction Data ◽  
Decagonal Quasicrystals ◽  
Resolution Electron ◽  
Structure Solution ◽  
Precession Electron Diffraction

The crystal structure of the novel Al77Rh15Ru8phase (which is an approximant of decagonal quasicrystals) was determined using modern direct methods (MDM) applied to automated electron diffraction tomography (ADT) data. The Al77Rh15Ru8E-phase is orthorhombic [Pbma,a= 23.40 (5),b= 16.20 (4) andc= 20.00 (5) Å] and has one of the most complicated intermetallic structures solved solely by electron diffraction methods. Its structural model consists of 78 unique atomic positions in the unit cell (19 Rh/Ru and 59 Al). Precession electron diffraction (PED) patterns and high-resolution electron microscopy (HRTEM) images were used for the validation of the proposed atomic model. The structure of the E-phase is described using hierarchical packing of polyhedra and a single type of tiling in the form of a parallelogram. Based on this description, the structure of the E-phase is compared with that of the ε6-phase formed in Al–Rh–Ru at close compositions.

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.

scholarly journals Hafnium-Silicon Precipitate Structure Determination in a New Heat-Resistant Ferritic Alloy by Precession Electron Diffraction Techniques

2013 ◽  
Vol 20 (1) ◽  
pp. 25-32 ◽  
Author(s):  
Désirée Viladot ◽  
Joaquim Portillo ◽  
Mauro Gemí ◽  
Stavros Nicolopoulos ◽  
Núria Llorca-Isern
Keyword(s):  
Electron Diffraction ◽  
Structure Determination ◽  
Three Dimensional ◽  
Direct Methods ◽  
Extinction Condition ◽  
Orbital Theory ◽  
Orthorhombic Unit Cell ◽  
Precession Angle ◽  
Ferritic Alloy ◽  
Precession Electron Diffraction

AbstractThe structure determination of an HfSi4 precipitate has been carried out by a combination of two precession electron diffraction techniques: high precession angle, 2.2°, single pattern collection at eight different zone axes and low precession angle, 0.5°, serial collection of patterns obtained by increasing tilts of 1°. A three-dimensional reconstruction of the associated reciprocal space shows an orthorhombic unit cell with parameters a = 11.4 Å, b = 11.8 Å, c = 14.6 Å, and an extinction condition of (hkl) h + k odd. The merged intensities from the high angle precession patterns have been symmetry tested for possible space groups (SG) fulfilling this condition and a best symmetrization residual found at 18% for SG 65 Cmmm. Use of the SIR2011 direct methods program allowed solving the structure with a structure residual of 18%. The precipitate objects of this study were reproducibly found in a newly implemented alloy, designed according to molecular orbital theory.

scholarly journals Ab initiostructure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detector

2016 ◽  
Vol 72 (2) ◽  
pp. 236-242 ◽  
Author(s):  
E. van Genderen ◽  
M. T. B. Clabbers ◽  
P. P. Das ◽  
A. Stewart ◽  
I. Nederlof ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Room Temperature ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Direct Methods ◽  
Liquid Nitrogen Temperature ◽  
High Dynamic Range ◽  
Electron Diffraction Data ◽  
High Signal

Until recently, structure determination by transmission electron microscopy of beam-sensitive three-dimensional nanocrystals required electron diffraction tomography data collection at liquid-nitrogen temperature, in order to reduce radiation damage. Here it is shown that the novel Timepix detector combines a high dynamic range with a very high signal-to-noise ratio and single-electron sensitivity, enablingab initiophasing of beam-sensitive organic compounds. Low-dose electron diffraction data (∼0.013 e− Å−2 s−1) were collected at room temperature with the rotation method. It was ascertained that the data were of sufficient quality for structure solution using direct methods using software developed for X-ray crystallography (XDS,SHELX) and for electron crystallography (ADT3D/PETS,SIR2014).

scholarly journals Towards Routine Structure Solution using Precession Electron Diffraction

2009 ◽  
Vol 15 (S2) ◽  
pp. 738-739
Author(s):  
PA Midgley ◽  
A Eggeman ◽  
T White ◽  
E Bithell
Keyword(s):  
Electron Diffraction ◽  
Structure Solution ◽  
Precession Electron Diffraction

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Strategies for full structure solution of intermetallic compounds using precession electron diffraction zonal data

2014 ◽  
Vol 47 (3) ◽  
pp. 1032-1041 ◽  
Author(s):  
Shmuel Samuha ◽  
Yaakov Krimer ◽  
Louisa Meshi
Keyword(s):  
Electron Diffraction ◽  
Intermetallic Compounds ◽  
Intermetallic Phase ◽  
Structure Type ◽  
Atomic Model ◽  
Coordination Polyhedra ◽  
Structure Solution ◽  
Precession Electron Diffraction ◽  
Full Structure ◽  
Merging Process

Owing to the individuality of intermetallic compounds, they are regarded as a special class of materials. As such, there is a need to develop a step-by-step methodology for solution of their structure. The current paper adapts the methodology of structure solution from precession electron diffraction (PED) zonal data for intermetallics. The optimization of PED parameters for structure determination was achieved through the development of the atomic model of a well known Mg17Al12(β) intermetallic phase. It was concluded that the PED acquisition parameters, the number of unique reflections and the quality of the merging process are the most important parameters that directly influence the correctness of a structure solution. The proposed methodology was applied to the structure solution of a highly complex new Mg48Al36Ag16phase, which was recently revealed in the Mg–Al–Ag system. The final atomic model consisted of 152 atoms in the unit cell, distributed over 23 unique atomic positions. The correctness of the atomic model was verified by the reasonability of the interatomic distances and coordination polyhedra formed. It was found that the experimental model of Φ-Al17.1Mg53.4Zn29.5can be assigned as a structure type for the Mg48Al36Ag16phase. The Δ value, which measures the similarity between two structures, was calculated as 0.040.

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