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 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.

Oxford HEXameter: Laboratory High Energy X-Ray Diffractometer for Bulk Residual Stress Analysis

2006 ◽  
Vol 524-525 ◽  
pp. 743-748 ◽  
Author(s):  
Alexander M. Korsunsky ◽  
Shu Yan Zhang ◽  
Daniele Dini ◽  
Willem J.J. Vorster ◽  
Jian Liu
Keyword(s):  
Accurate Determination ◽  
High Energy ◽  
Energy Dispersive ◽  
Detector Response ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
New Instrument ◽  
Synchrotron Beamlines

Diffraction of penetrating radiation such as neutrons or high energy X-rays provides a powerful non-destructive method for the evaluation of residual stresses in engineering components. In particular, strain scanning using synchrotron energy-dispersive X-ray diffraction has been shown to offer a fast and highly spatially resolving measurement technique. Synchrotron beamlines provide best available instruments in terms of flux and low beam divergence, and hence spatial and measurement resolution and data collection rate. However, despite the rapidly growing number of facilities becoming available in Europe and across the world, access to synchrotron beamlines for routine industrial and research use remains regulated, comparatively slow and expensive. A laboratory high energy X-ray diffractometer for bulk residual strain evaluation (HEXameter) has been developed and built at Oxford University. It uses a twin-detector setup first proposed by one of the authors in the energy dispersive X-ray diffraction mode and allows simultaneous determination of macroscopic and microscopic strains in two mutually orthogonal directions that lie approximately within the plane normal to the incident beam. A careful procedure for detector response calibration is used in order to facilitate accurate determination of lattice parameters by pattern refinement. The results of HEXameter measurements are compared with synchrotron X-ray data for several samples e.g. made from a titanium alloy and a particulate composite with an aluminium alloy matrix. Experimental results are found to be consistent with synchrotron measurements and strain resolution close to 2×10-4 is routinely achieved by the new instrument.

scholarly journals Comparison of Pipette and Laser Diffraction Methods in Determining the Granulometric Content of Fluvial Sediment Samples

2013 ◽  
Vol 6 (3-4) ◽  
pp. 49-54 ◽  
Author(s):  
Ágnes Kun ◽  
Orsolya Katona ◽  
György Sipos ◽  
Károly Barta
Keyword(s):  
Grain Size ◽  
Size Range ◽  
Accurate Determination ◽  
Diffraction Method ◽  
Laser Diffraction ◽  
Detailed Data ◽  
Fluvial Sediment ◽  
Sediment Samples ◽  
Correlation Factors

Abstract Nowadays there is a growing demand for rapid and accurate determination of grain size distribution. The conventional pipette method is time-consuming and provides less detailed data compared to recently introduced methods. However, in Hungarian practice the pipette method is still considered to be the standard one, as there are a long series of measurements, and grain size thresholds used in sedimentology and soil sciences are based on this approach. The aim of our research was to determine the comparability of the laser diffraction method (LDM) with the conventional pipette method (PM), in order to investigate the controversial question on the interchangeability of the two methods. Based on our measurements on some representative fluvial sediment samples, we found that the largest difference in results can be expected in the silty grain size range. However if the main fractions (clay, silt, sand) are considered the methods provided similar very results, and correlation factors were above 0.92. In all, the LDM has a clear advantage because of its speed, reproducibility and fewer possibilities for operator failure.

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.

Energy-Dispersive X-Ray Techniques for Accurate Heavy Element Assay

1986 ◽  
Vol 30 ◽  
pp. 285-292 ◽  
Author(s):  
H. Ottmar ◽  
H. Eberle ◽  
P. Matussek ◽  
I. Michel-Piper
Keyword(s):  
Absorption Edge ◽  
Heavy Element ◽  
Accurate Determination ◽  
Energy Dispersive ◽  
X Rays ◽  
Specific Absorption ◽  
X Ray ◽  
Xrf Analysis ◽  
Analysis Technique

Energy-dispersive X-ray techniques can be employed in two different ways for the accurate determination of element concentrations in specimens: (1) spectrometry of fluoresced characteristic X-rays as widely applied in the various modes of the traditional XRF analysis technique, and (2) spectrometry of the energy-differential transmittance of an X-ray continuum at the element-specific absorption-edge energies.

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.

scholarly journals Clustering of atomic displacement parameters in bovine trypsin reveals a distributed lattice of atoms with shared chemical properties

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Viktor Ahlberg Gagnér ◽  
Ida Lundholm ◽  
Maria-Jose Garcia-Bonete ◽  
Helena Rodilla ◽  
Ran Friedman ◽  
...  
Keyword(s):  
Protein Dynamics ◽  
Structural Information ◽  
Low Frequency ◽  
Chemical Properties ◽  
Atomic Displacement ◽  
Thz Radiation ◽  
X Ray Crystallography ◽  
Bovine Trypsin ◽  
Main Challenge ◽  
Atomic Displacement Parameters

AbstractLow-frequency vibrations are crucial for protein structure and function, but only a few experimental techniques can shine light on them. The main challenge when addressing protein dynamics in the terahertz domain is the ubiquitous water that exhibit strong absorption. In this paper, we observe the protein atoms directly using X-ray crystallography in bovine trypsin at 100 K while irradiating the crystals with 0.5 THz radiation alternating on and off states. We observed that the anisotropy of atomic displacements increased upon terahertz irradiation. Atomic displacement similarities developed between chemically related atoms and between atoms of the catalytic machinery. This pattern likely arises from delocalized polar vibrational modes rather than delocalized elastic deformations or rigid-body displacements. The displacement correlation between these atoms were detected by a hierarchical clustering method, which can assist the analysis of other ultra-high resolution crystal structures. These experimental and analytical tools provide a detailed description of protein dynamics to complement the structural information from static diffraction experiments.

RADIATION CHEMISTRY INVESTIGATION OF AQUEOUS SOLUTIONS USING P32 AND S35 AS INTERNAL SOURCES

1952 ◽  
Vol 30 (1) ◽  
pp. 39-46 ◽  
Author(s):  
T. J. Hardwick
Keyword(s):  
Accurate Determination ◽  
Chemical Change ◽  
Radiation Chemistry ◽  
X Rays ◽  
Γ Radiation ◽  
Unit Energy ◽  
Chemical Dosimetry ◽  
Ceric Ion ◽  
Internal Sources

The oxidation of ferrous ion and the reduction of ceric ion in 0.80  N sulphuric acid by electrons from dissolved P32 and S35 have been studied. The chemical yields (chemical change per unit energy absorbed) obtained agree well with those obtained using X or γ-radiation. The yield is independent of electron energy above about 5 kev. The results show that chemical dosimetry methods may be used for the accurate determination of energy absorption for electron energies as low as 45 kev. or X rays of 200 kev.

Sign in / Sign up

Export Citation Format

Share Document