scholarly journals Using Complementary Methods of Synchrotron Radiation Powder Diffraction and Pair Distribution Function to Refine Crystal Structures with High Quality Parameters—A Review

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 124 ◽  
Author(s):  
Seungyeol Lee ◽  
Huifang Xu
Keyword(s):  
Distribution Function ◽  
Synchrotron Radiation ◽  
Single Crystal ◽  
Powder Diffraction ◽  
Pair Distribution Function ◽  
Atomic Displacement ◽  
High Quality ◽  
X Ray ◽  
Complementary Methods ◽  
Atomic Displacement Parameters

Determination of the atomic-scale structures of certain fine-grained minerals using single-crystal X-ray diffraction (XRD) has been challenging because they commonly occur as submicron and nanocrystals in the geological environment. Synchrotron powder diffraction and scattering techniques are useful complementary methods for studying this type of minerals. In this review, we discussed three example studies investigated by combined methods of synchrotron radiation XRD and pair distribution function (PDF) techniques: (1) low-temperature cristobalite; (2) kaolinite; and (3) vernadite. Powder XRD is useful to determine the average structure including unit-cell parameters, fractional atomic coordinates, occupancies and isotropic atomic displacement parameters. X-ray/Neutron PDF methods are sensitive to study the local structure with anisotropic atomic displacement parameters (ADP). The results and case studies suggest that the crystal structure and high-quality ADP values can be obtained using the combined methods. The method can be useful to characterize crystals and minerals that are not suitable for single-crystal XRD.

scholarly journals Crystal Structure of Moganite and Its Anisotropic Atomic Displacement Parameters Determined by Synchrotron X-ray Diffraction and X-ray/Neutron Pair Distribution Function Analyses

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 272
Author(s):  
Seungyeol Lee ◽  
Huifang Xu ◽  
Hongwu Xu ◽  
Joerg Neuefeind
Keyword(s):  
Crystal Structure ◽  
Distribution Function ◽  
Single Crystal ◽  
Pair Distribution Function ◽  
Atomic Displacement ◽  
Single Crystal Xrd ◽  
X Ray Diffraction ◽  
X Ray ◽  
Neutron Pair ◽  
Atomic Displacement Parameters

The crystal structure of moganite from the Mogán formation on Gran Canaria has been re-investigated using high-resolution synchrotron X-ray diffraction (XRD) and X-ray/neutron pair distribution function (PDF) analyses. Our study for the first time reports the anisotropic atomic displacement parameters (ADPs) of a natural moganite. Rietveld analysis of synchrotron XRD data determined the crystal structure of moganite with the space group I2/a. The refined unit-cell parameters are a = 8.7363(8), b = 4.8688(5), c = 10.7203(9) Å, and β = 90.212(4)°. The ADPs of Si and O in moganite were obtained from X-ray and neutron PDF analyses. The shapes and orientations of the anisotropic ellipsoids determined from X-ray and neutron measurements are similar. The anisotropic ellipsoids for O extend along planes perpendicular to the Si-Si axis of corner-sharing SiO4 tetrahedra, suggesting precession-like movement. Neutron PDF result confirms the occurrence of OH over some of the tetrahedral sites. We postulate that moganite nanomineral is stable with respect to quartz in hypersaline water. The ADPs of moganite show a similar trend as those of quartz determined by single-crystal XRD. In short, the combined methods can provide high-quality structural parameters of moganite nanomineral, including its ADPs and extra OH position at the surface. This approach can be used as an alternative means for solving the structures of crystals that are not large enough for single-crystal XRD measurements, such as fine-grained and nanocrystalline minerals formed in various geological environments.

Using powder XRD and pair distribution function to determine anisotropic atomic displacement parameters of orthorhombic tridymite and tetragonal cristobalite

2019 ◽  
Vol 75 (2) ◽  
pp. 160-167 ◽  
Author(s):  
Seungyeol Lee ◽  
Huifang Xu
Keyword(s):  
Distribution Function ◽  
Low Temperature ◽  
Single Crystal ◽  
Pair Distribution Function ◽  
Atomic Displacement ◽  
Single Crystal Xrd ◽  
Cell Parameters ◽  
Fine Grained ◽  
Transmission Electron ◽  
Atomic Displacement Parameters

Determination of the crystal structures of low-temperature tridymite and cristobalite using single-crystal XRD has been challenging because they generally occur as metastable fine-grained crystals in the geological environment. Therefore, using powder diffraction and scattering techniques is critical to study the low-temperature crystals. Synchrotron powder X-ray diffraction (XRD), pair distribution function (PDF) and transmission electron microscopy were used to investigate the structure of orthorhombic tridymite with C2221 symmetry and tetragonal cristobalite with P41212 symmetry, including their anisotropic atomic displacement parameters (ADPs). Rietveld refinement was used to determine the unit-cell parameters, fractional coordinates and isotropic atomic displacement parameters (U iso) of the tridymite and cristobalite. The PDF method was used to determine ADPs for each atom. The results suggest that the crystal structure with high quality ADP values can be obtained using the combined methods of XRD and PDF analyses. The method can be used for characterizing crystals that are not suitable for single-crystal XRD.

scholarly journals A simple correction for the parallax effect in X-ray pair distribution function measurements

2019 ◽  
Vol 52 (5) ◽  
pp. 1072-1076 ◽  
Author(s):  
Frederick Marlton ◽  
Oleh Ivashko ◽  
Martin v. Zimmerman ◽  
Olof Gutowski ◽  
Ann-Christin Dippel ◽  
...  
Keyword(s):  
Distribution Function ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Pair Distribution Function ◽  
Reference Data ◽  
Real Space ◽  
X Ray ◽  
Local Structures ◽  
Pdf Analysis ◽  
Complex Nanostructures

Total scattering and pair distribution function (PDF) analysis has created new insights that traditional powder diffraction methods have been unable to achieve in understanding the local structures of materials exhibiting disorder or complex nanostructures. Care must be taken in such analyses as subtle and discrete features in the PDF can easily be artefacts generated in the measurement process, which can result in unphysical models and interpretation. The focus of this study is an artefact called the parallax effect, which can occur in area detectors with thick detection layers during the collection of X-ray PDF data. This effect results in high-Q peak offsets, which subsequently cause an r-dependent shift in the PDF peak positions in real space. Such effects should be accounted for if a truly accurate model is to be achieved, and a simple correction that can be conducted via a Rietveld refinement against the reference data is proposed.

scholarly journals Single-crystal neutron and X-ray diffraction study of garnet-type solid-state electrolyte Li6La3ZrTaO12: an in situ temperature-dependence investigation (2.5 ≤ T ≤ 873 K)

2021 ◽  
Vol 77 (1) ◽  
pp. 123-130
Author(s):  
Günther J. Redhammer ◽  
Martin Meven ◽  
Steffen Ganschow ◽  
Gerold Tippelt ◽  
Daniel Rettenwander
Keyword(s):  
Solid State ◽  
Single Crystal ◽  
Czochralski Method ◽  
Atomic Displacement ◽  
X Ray Diffraction ◽  
Solid State Electrolyte ◽  
Cubic Symmetry ◽  
X Ray ◽  
Site Occupation ◽  
Atomic Displacement Parameters

Large single crystals of garnet-type Li6La3ZrTaO12 (LLZTO) were grown by the Czochralski method and analysed using neutron diffraction between 2.5 and 873 K in order to fully characterize the Li atom distribution, and possible Li ion mobility in this class of potential candidates for solid-state electrolyte battery material. LLZTO retains its cubic symmetry (space group Ia 3 d) over the complete temperature range. When compared to other sites, the octahedral sites behave as the most rigid unit and show the smallest increase in atomic displacement parameters and bond length. The La and Li sites show similar thermal expansion in their bond lengths with temperature, and the anisotropic and equivalent atomic displacement parameters exhibit a distinctly larger increase at temperatures above 400 K. Detailed inspection of nuclear densities at the Li1 site reveal a small but significant displacement from the 24d position to the typical 96h position, which cannot, however, be resolved from the single-crystal X-ray diffraction data. The site occupation of LiI ions on Li1 and Li2 sites remains constant, so there is no change in site occupation with temperature.

Localversusaverage structure: a study of neighborite (NaMgF3) utilizing the pair distribution function method for structure determination

2007 ◽  
Vol 40 (3) ◽  
pp. 441-448 ◽  
Author(s):  
C. David Martin ◽  
Peter J. Chupas ◽  
Karena W. Chapman ◽  
John B. Parise
Keyword(s):  
Distribution Function ◽  
Local Structure ◽  
Pair Distribution Function ◽  
Statistical Modelling ◽  
Atomic Displacement ◽  
High Energy ◽  
Temperature Dependent ◽  
X Ray Scattering ◽  
Atomic Displacement Parameters ◽  
Temperature Asymmetry

The temperature-dependent local structure (< 2 nm) of neighborite (NaMgF3) is probed through least-squares refinement of structure models fit to the pair distribution function [G(r)] derived from the total high-energy X-ray scattering of sample powders. In contrast to previous temperature-dependent structure models obtained through Rietveld refinement and statistical modelling of powder diffraction data, it is found that the average Mg—F bond length, corresponding to a ∼2 Å peak in theG(r), increases between 323 and 1123 K. At each temperature, asymmetry in this peak is consistent with an orthorhombic (Pbnm) perovskite local structure, allowing three unique Mg—F values and deformation of MgF6octahedra. Defined by the three orthogonal Mg—Mg distances, the pseudo-cubic unit cell of local structure models becomes metrically tetragonal and cubic at temperatures greater than ∼623 and 1038 K, respectively. A discontinuity in the temperature dependence of the fluorine atomic displacement parameters at 1038 K suggests thermal activation of new vibrational modes in NaMgF3at high temperature, consistent with transverse vibration of the bridging fluorine atoms (Mg—F—Mg).

scholarly journals Electron diffraction, X-ray powder diffraction and pair-distribution-function analyses to determine the crystal structures of Pigment Yellow 213, C23H21N5O9

2009 ◽  
Vol 65 (2) ◽  
pp. 189-199 ◽  
Author(s):  
Martin U. Schmidt ◽  
Stefan Brühne ◽  
Alexandra K. Wolf ◽  
Anette Rech ◽  
Jürgen Brüning ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Distribution Function ◽  
Electron Diffraction ◽  
Powder Diffraction ◽  
Pair Distribution Function ◽  
Structural Information ◽  
Domain Size ◽  
X Ray ◽  
Β Phase ◽  
Α Phase

The crystal structure of the nanocrystalline α phase of Pigment Yellow 213 (P.Y. 213) was solved by a combination of single-crystal electron diffraction and X-ray powder diffraction, despite the poor crystallinity of the material. The molecules form an efficient dense packing, which explains the observed insolubility and weather fastness of the pigment. The pair-distribution function (PDF) of the α phase is consistent with the determined crystal structure. The β phase of P.Y. 213 shows even lower crystal quality, so extracting any structural information directly from the diffraction data is not possible. PDF analysis indicates the β phase to have a columnar structure with a similar local structure as the α phase and a domain size in column direction of approximately 4 nm.

Development and application of laboratory X-ray fluorescence holography equipment

2004 ◽  
Vol 19 (1) ◽  
pp. 77-80 ◽  
Author(s):  
Y. Takahashi ◽  
K. Hayashi ◽  
E. Matsubara
Keyword(s):  
Synchrotron Radiation ◽  
Single Crystal ◽  
Counting Rate ◽  
Three Dimensional ◽  
High Quality ◽  
High Counting Rate ◽  
X Ray ◽  
Graphite Monochromator ◽  
Fluorescent Radiation ◽  
Atomic Image

The X-ray fluorescence holography (XFH) method has drawn the attention of many researchers as a novel experimental technique for imaging a three-dimensional local atomic structure around a certain element in a single crystal. Synchrotron radiation (SR) has been mainly used for the measurements because of extremely weak signals that are about 0.3% of isotropic fluorescent radiation. The measurements limited to the use of a SR source clearly hinder from increasing the number of the users. Thus, we developed a laboratory XFH equipment with a conventional X-ray source by using a singly bent graphite monochromator with a large curvature and X-ray detector for a high counting rate. With this equipment, we have successfully demonstrated that high-quality hologram data of a gold single crystal almost equivalent to those with a SR source are obtained. Four different holograms are recorded in the normal and inverse XFH modes. An atomic image reconstructed from these holograms patterns shows a distinct atomic image of Au

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