Structural refinements of the individual grains within polycrystals and powders

2003 ◽  
Vol 36 (2) ◽  
pp. 326-332 ◽  
Author(s):  
S. Schmidt ◽  
H. F. Poulsen ◽  
G. B. M. Vaughan
Keyword(s):  
Grain Size ◽  
Atomic Displacement ◽  
X Rays ◽  
Structural Refinement ◽  
Gauge Volume ◽  
Euler Space ◽  
Grain Orientations ◽  
Atomic Displacement Parameters ◽  
The Individual ◽  
Individual Grains

A method is presented for simultaneous structural refinement of up to several hundred grains inside powders or polycrystals. The method is based on the use of hard X-rays and the indexing programGRAINDEX, where grain orientations are found by scanning in Euler space. Conventional experimental setups and refinement programs for single-crystal work can be applied. The method is validated by a study of a sintered plate of α-Al2O3, containing of the order of 1500 grains in the gauge volume. 57 of the largest grains were refined with respect to the Alzand Oxpositions as well as the isotropic atomic displacement parameters. TheR1 values were 3.4% and 3.8% for the grain average and the best grain, respectively. A discussion of the potential of the method is presented, as well as the main limitation: grain size and overlap of diffraction spots.

The correction of reflection intensities for incomplete absorption of high-energy X-rays in the CCD phosphor

2002 ◽  
Vol 35 (3) ◽  
pp. 356-359 ◽  
Author(s):  
G. Wu ◽  
B. L. Rodrigues ◽  
P. Coppens
Keyword(s):  
Incident Angle ◽  
Atomic Displacement ◽  
High Energy ◽  
X Rays ◽  
Structural Refinement ◽  
Data Set ◽  
X Ray ◽  
Area Detector ◽  
Angle Dependence ◽  
Atomic Displacement Parameters

It is shown that incomplete absorption of the X-ray beam in the phosphor of an area detector causes an incident-angle dependence of the recorded X-ray intensities. An energy scan of a SMART-6000 CCD (charge-coupled device) phosphor using synchrotron radiation shows the correction to be of importance above about 17 keV. Intensities of single reflections, each collected several times at different angles of incidence on the phosphor surface, show a pronounced angle-dependence at shorter wavelengths. Both conventional structural refinement and multipole charge density studies confirm that an oblique-incidence correction leads to improved quality of the results. Atomic displacement parameters will be systematically biased when the correction is not applied. For a λ = 0.394 Å data set, neglecting the correction gives rise to artifacts in the deformation density maps that are likely to lead to misinterpretation of the experimental results.

Tracking: a method for structural characterization of grains in powders or polycrystals

2001 ◽  
Vol 34 (6) ◽  
pp. 744-750 ◽  
Author(s):  
E. M. Lauridsen ◽  
S. Schmidt ◽  
R. M. Suter ◽  
H. F. Poulsen
Keyword(s):  
High Energy ◽  
X Rays ◽  
Rotation Method ◽  
Euler Space ◽  
On Line ◽  
The Individual ◽  
Individual Grains ◽  
Non Destructive ◽  
Non Destructive Characterization

A method is presented for fast and non-destructive characterization of the individual grains inside bulk materials (powders or polycrystals). The positions, volumes and orientations of hundreds of grains are determined simultaneously. An extension of the rotation method is employed: a monochromatic beam of high-energy X-rays, focused in one dimension, impinges on the sample and the directions of the diffracted beams are traced by translation of two-dimensional detectors. Algorithms suitable for on-line analysis are described, including a novel indexing approach, where the crystal symmetry is used directly by scanning in Euler space. The method is verified with a simulation of 100 grains.

Neutron powder diffraction studies as a function of temperature of structure II hydrate formed from propane

2003 ◽  
Vol 81 (1-2) ◽  
pp. 431-438 ◽  
Author(s):  
C J Rawn ◽  
A J Rondinone ◽  
B C Chakoumakos ◽  
S Circone ◽  
L A Stern ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Structure Type ◽  
Atomic Displacement ◽  
Host Lattice ◽  
Neutron Powder Diffraction ◽  
Lattice Data ◽  
Structural Refinement ◽  
Neutron Powder Diffraction Data ◽  
Atomic Displacement Parameters ◽  
Atomic Coordinates

Neutron powder diffraction data confirm that hydrate samples synthesized with propane crystallize as structure type II hydrate. The structure has been modeled using rigid-body constraints to describe C3H8 molecules located in the eight larger polyhedral cavities of a deuterated host lattice. Data were collected at 12, 40, 100, 130, 160, 190, 220, and 250 K and used to calculate the thermal expansivity from the temperature dependence of the lattice parameters. The data collected allowed for full structural refinement of atomic coordinates and the atomic-displacement parameters. PACS No.: 61.12-q

scholarly journals Multilayer Diffraction Reveals That Colloidal Superlattices Approach the Structural Perfection of Single Crystals

2020 ◽  
Author(s):  
Stefano Toso ◽  
Dmitry Baranov ◽  
Davide Altamura ◽  
Francesco Scattarella ◽  
Jakob Dahl ◽  
...  
Keyword(s):  
Structural Information ◽  
Accurate Determination ◽  
Diffraction Method ◽  
Atomic Displacement ◽  
Interparticle Spacing ◽  
X Rays ◽  
Structural Perfection ◽  
Fitting Algorithm ◽  
Atomic Displacement Parameters

Colloidal superlattices are fascinating materials made of ordered nanocrystals, yet they are rarely called “atomically precise.” That is unsurprising, given how challenging it is to quantify the degree of structural order in these materials. However, once that order crosses a certain threshold, constructive interference of X-rays diffracted by the nanocrystals dominates the diffraction pattern, offering a wealth of structural information. By treating nanocrystals as scattering sources forming a self-probing interferometer, we developed a multilayer diffraction method that enabled the accurate determination of nanocrystal size, interparticle spacing, and their fluctuations for samples of self-assembled CsPbBr<sub>3</sub> and PbS nanomaterials. The average nanocrystal displacement of 0.32-1.4 Å in the studied superlattices provides a figure of merit for their structural perfection and approaches the atomic displacement parameters found in traditional crystals. The method requires a laboratory-grade diffractometer and an open-source fitting algorithm for data analysis, providing a competitive alternative to resource-intensive synchrotron experiments.

scholarly journals Atomic resolution studies of carbonic anhydrase II

2010 ◽  
Vol 66 (5) ◽  
pp. 616-627 ◽  
Author(s):  
Craig A. Behnke ◽  
Isolde Le Trong ◽  
Jeff W. Godden ◽  
Ethan A. Merritt ◽  
David C. Teller ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Structural Similarity ◽  
Atomic Displacement ◽  
Atomic Resolution ◽  
Protein Surfaces ◽  
X Ray ◽  
Density Maps ◽  
Structural Details ◽  
Atomic Displacement Parameters ◽  
The Individual

Carbonic anhydrase has been well studied structurally and functionally owing to its importance in respiration. A large number of X-ray crystallographic structures of carbonic anhydrase and its inhibitor complexes have been determined, some at atomic resolution. Structure determination of a sulfonamide-containing inhibitor complex has been carried out and the structure was refined at 0.9 Å resolution with anisotropic atomic displacement parameters to anRvalue of 0.141. The structure is similar to those of other carbonic anhydrase complexes, with the inhibitor providing a fourth nonprotein ligand to the active-site zinc. Comparison of this structure with 13 other atomic resolution (higher than 1.25 Å) isomorphous carbonic anhydrase structures provides a view of the structural similarity and variability in a series of crystal structures. At the center of the protein the structures superpose very well. The metal complexes superpose (with only two exceptions) with standard deviations of 0.01 Å in some zinc–protein and zinc–ligand bond lengths. In contrast, regions of structural variability are found on the protein surface, possibly owing to flexibility and disorder in the individual structures, differences in the chemical and crystalline environments or the different approaches used by different investigators to model weak or complicated electron-density maps. These findings suggest that care must be taken in interpreting structural details on protein surfaces on the basis of individual X-ray structures, even if atomic resolution data are available.

An Application of Multigrain Approaches to the Structural Solution of Grains from Polycrystalline Samples

2019 ◽  
Vol 288 ◽  
pp. 119-123 ◽  
Author(s):  
Jav Davaasambuu ◽  
Jon Wright ◽  
Henning O. Soerensen ◽  
Soeren Schmidt ◽  
Henning F. Poulsen ◽  
...  
Keyword(s):  
Structural Refinement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Experimental Parameters ◽  
Resolution Level ◽  
Diffraction Patterns ◽  
The Individual ◽  
Individual Grains ◽  
Comparison Of The Results ◽  
Good Agreement

The overlap of diffraction spots from different grains was investigated to understand the influence of experimental factors on the x-ray diffraction data quality and to optimize the experimental parameters for data collection on polycrystalline samples. Diffraction patterns for photoactive polycrystals were indexed and sorted with respect to grains using multigrain approaches. The indexing of diffraction spots and the identification of grains for tetrathiafulvalene-p-chloranil samples were performed using the ImageD11, GrainSpotter, GRAINDEX and Cell_now programs. In many cases, comparison of the results from these programs shows good agreement. For the individual grains from polycrystalline samples, the crystal structure was solved and refined using the SHELXTL program. After the structural refinement of the grains, the best and the average R1 values were 1.93% and 2.06%, respectively, which are on a comparable resolution level with that obtained from the x-ray single crystal measurements.

scholarly journals Variation in the autoradiographic technique: I. Emulsion-developer combinations assessed by photometric measurement of single silver grains.

1976 ◽  
Vol 24 (10) ◽  
pp. 1057-1064 ◽  
Author(s):  
J E Neely ◽  
J W Combs
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Silver Particle ◽  
Development Time ◽  
Television Camera ◽  
The Individual ◽  
Individual Grains ◽  
Autoradiographic Technique ◽  
Silver Grains ◽  
Maximum Development

Five commonly used developers (Acufine, Rodinal, Dektol, D19 and Microdol X) and two popular nuclear gel emulsions (Kodak NTB-2 and Ilford L4) were tested in combinations for adequacy of development characteristics and the distribution of silver particle (grain) size measured by means of a reflectance microphotometer. All developer-emulsion combinations had some range of development time during which maximum development was accomplished with no occurrence of background grains, with the exceptions of the combinations of NTB2-Acufine and NTB2-D19. Ilford L4 emulsion obtained the narrowest grain size distribution with Rodinal and Acufine, followed by Dektol, and D19. The narrowest size distribution for Kodak NTB2 emulsion was achieved with D19 followed by Acufine, Dektol and Rodinal. Microdol-X had undesirable effects on the integrity of the individual grains of both emulsions. The criteria are discussed for selecting the most advantageous emulsion-developer system for the particular mode of evaluation (visual, photometric, television camera) to be applied to the finished autoradiographic specimens.

Three-Dimensional X-Ray Diffraction Microscopy Using High-Energy X-Rays

MRS Bulletin ◽  
2004 ◽  
Vol 29 (3) ◽  
pp. 166-169 ◽  
Author(s):  
Henning F. Poulsen ◽  
Dorte Juul Jensen ◽  
Gavin B.M. Vaughan
Keyword(s):  
Materials Science ◽  
Three Dimensional ◽  
High Energy ◽  
Polycrystalline Materials ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Reconstruction Methods ◽  
The Individual ◽  
Individual Grains

AbstractThree-dimensional x-ray diffraction (3DXRD) microscopy is a tool for fast and nondestructive characterization of the individual grains, subgrains, and domains inside bulk materials. The method is based on diffraction with very penetrating hard x-rays (E ≥ 50 keV), enabling 3D studies of millimeter-to-centimeter-thick specimens.The position, volume, orientation, and elastic and plastic strain can be derived for hundreds of grains simultaneously. Furthermore, by applying novel reconstruction methods, 3D maps of the grain boundaries can be generated. The 3DXRD microscope in use at the European Synchrotron Radiation Facility in Grenoble, France, has a spatial resolution of ∼5 μm and can detect grains as small as 150 nm. The technique enables, for the first time, dynamic studies of the individual grains within polycrystalline materials. In this article, some fundamental materials science applications of 3DXRD are reviewed: studies of nucleation and growth kinetics during recrystallization, recovery, and phase transformations, as well as studies of polycrystal deformation.

3DXRD – Mapping Grains and Their Dynamics in 3 Dimensions

2004 ◽  
Vol 467-470 ◽  
pp. 1363-1372 ◽  
Author(s):  
Henning Friis Poulsen ◽  
Xing Fu ◽  
Erik Knudsen ◽  
Erik M. Lauridsen ◽  
L. Margulies ◽  
...  
Keyword(s):  
European Synchrotron Radiation Facility ◽  
Polycrystalline Materials ◽  
X Rays ◽  
X Ray Diffraction ◽  
Time Dynamic ◽  
3 Dimensional ◽  
Reconstruction Methods ◽  
Set Up ◽  
The Individual ◽  
Individual Grains

3-Dimensional X-Ray Diffraction (3DXRD) microscopy is a tool for fast and non-destructive characterization of the individual grains, sub-grains and domains inside bulk materials. The method is based on diffraction with highly penetrating hard x-rays, enabling 3D studies of millimeter - centimeter thick specimens. The position, volume, orientation, elastic and plastic strain can be derived for hundreds of grains simultaneously. Furthermore, by applying novel reconstruction methods 3D maps of the grain boundaries can be generated. With the present 3DXRD microscope set-up at the European Synchrotron Radiation Facility, the spatial resolution is ~ 5 µm, while grains of size 100 nm can be detected. 3DXRD microscopy enables, for the first time, dynamic studies of the individual grains and sub-grains within polycrystalline materials. The methodology is reviewed with emphasis on recent advances in grain mapping. Based on this a series of general 3DXRD approaches are identified for studies of nucleation and growth phenomena such as recovery, recrystallisation and grain growth in metals.

Three-dimensional maps of grain boundaries and the stress state of individual grains in polycrystals and powders

2001 ◽  
Vol 34 (6) ◽  
pp. 751-756 ◽  
Author(s):  
H. F. Poulsen ◽  
S. F. Nielsen ◽  
E. M. Lauridsen ◽  
S. Schmidt ◽  
R. M. Suter ◽  
...  
Keyword(s):  
Stress State ◽  
Grain Boundaries ◽  
Tensile Deformation ◽  
Strain Tensor ◽  
Three Dimensional ◽  
High Energy ◽  
European Synchrotron Radiation Facility ◽  
X Rays ◽  
The Individual ◽  
Individual Grains

A fast and non-destructive method for generating three-dimensional maps of the grain boundaries in undeformed polycrystals is presented. The method relies on tracking of micro-focused high-energy X-rays. It is verified by comparing an electron microscopy map of the orientations on the 2.5 × 2.5 mm surface of an aluminium polycrystal with tracking data produced at the 3DXRD microscope at the European Synchrotron Radiation Facility. The average difference in grain boundary position between the two techniques is 26 µm, comparable with the spatial resolution of the 3DXRD microscope. As another extension of the tracking concept, algorithms for determining the stress state of the individual grains are derived. As a case study, 3DXRD results are presented for the tensile deformation of a copper specimen. The strain tensor for one embedded grain is determined as a function of load. The accuracy on the strain is Δ∊ ≃ 10−4.

Sign in / Sign up

Export Citation Format

Share Document