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 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.

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.

Thermoelectric properties of a Mn substituted synthetic tetrahedrite

2015 ◽  
Vol 17 (3) ◽  
pp. 1716-1727 ◽  
Author(s):  
Raju Chetty ◽  
Prem Kumar D. S. ◽  
Gerda Rogl ◽  
Peter Rogl ◽  
Ernst Bauer ◽  
...  
Keyword(s):  
Single Crystal ◽  
Detailed Analysis ◽  
Thermoelectric Properties ◽  
Atomic Displacement ◽  
Single Crystal Xrd ◽  
Atomic Displacement Parameters

In this paper, a detailed analysis of atomic displacement parameters for the compound Cu10.6Mn1.4Sb4S13 using single crystal XRD has been discussed.

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).

The Characterization Of Chemical Bath Deposited Cds On Single Crystal InP Substrates

1997 ◽  
Vol 485 ◽  
Author(s):  
G. M. Riker ◽  
M. M. Al-Jassim ◽  
F. S. Hasoon
Keyword(s):  
Electron Microscopy ◽  
Single Crystal ◽  
Surface Cleaning ◽  
Film Morphology ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Fine Grained ◽  
Transmission Electron ◽  
Cds Thin Films ◽  
Inp Substrates

AbstractWe have investigated CdS thin films as possible passivating window layers for InP. The films were deposited on single crystal InP by chemical bath deposition (CBD). The film thickness, as optically determined by ellipsometry, was varied from 500 to 840Å. The film morphology was investigated by high resolution scanning electron microscopy (SEM), whereas the film microstructure was studied by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM). Most of the films were fine-grained polycrystalline CdS, with some deposition conditions resulting in epitaxial growth. Cross-sectional TEM examination revealed the presence of interface contaminants. The effect of such contaminants on the film morphology and microstructure was studied, and various approaches for InP surface cleaning/treatment were investigated. The epitaxial films were determined to be hexagonal on both the (111) and (100) InP substrates; however, they were heavily faulted.

Embreyite: structure determination, chemical formula and comparative crystal chemistry

2018 ◽  
Vol 82 (2) ◽  
pp. 275-290 ◽  
Author(s):  
Vadim M. Kovrugin ◽  
Oleg I. Siidra ◽  
Igor V. Pekov ◽  
Nikita V. Chukanov ◽  
Dmitry A. Khanin ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Microprobe Analysis ◽  
Direct Methods ◽  
Structural Similarity ◽  
Structural Type ◽  
Unit Cell ◽  
Single Crystal Xrd ◽  
Cell Parameters ◽  
Distorted Octahedra

ABSTRACTEmbreyite from the Berezovskoe, Urals, Russia, was studied by the means of powder X-ray diffraction (XRD), single-crystal XRD, infrared spectroscopy and microprobe analysis. The empirical formula of embreyite obtained on the basis of microprobe analysis is Pb1.29Cu0.07Cr0.52P0.43O4(without taking into account the presence of H2O). An examination of single-crystal XRD frames of the tested crystals cut from embreyite intergrowths revealed split reflection spots of weak intensities, even after a long exposure time. The crystal structure of embreyite (monoclinic,C2/m,a= 9.802(16),b= 5.603(9),c= 7.649(12) Å, β = 114.85(3)oandV= 381.2(11) Å3) has been solved by direct methods and refined toR1= 0.050 for 318 unique observed reflections. The powder XRD patterns of the holotype embreyite and the fresh material studied are close in bothdvalues and the intensities match the pattern calculated from the structural single-crystal XRD data. The unit-cell parameters were re-calculated for the holotype sample using a new cell setting and correspondinghklindices. The crystal structure of embreyite is based on layers formed by corner-sharing mixed chromate-phosphate tetrahedra and PbO6distorted octahedra. The interlayer space is filled by disordered Pb2+and Cu2+cations. Generally, the crystal structure of embreyite can be referred to the structural type of palmierite. {Pb[(Cr,P)O4]2]} layers in embreyite are similar in topology to those in yavapaiite-type compounds. The general formula of embreyite can be represented as (Pbx$M_y^{2 +} $□1–x–y)2{Pb[(Cr,P)O4]2}(H2O)n, whereM2+= Cu and Zn and 0.5 ≤x+y≤ 1, or, in the simplified form: (Pb,Cu,□)2{Pb[(Cr,P)O4]2}(H2O)n. The simplified formula of embreyite is similar in stoichiometry to vauquelinite and may explain the existence of the solid-solution series. The determination of the crystal structure of embreyite may also help to resolve the crystal chemical nature of cassedanneite. The XRD pattern of cassedanneite contains a distinct reflection withd= 13.9 Å, forbidden for the embreyite unit cell. This feature may indicate the doubling of thecunit-cell parameter of cassedanneite in comparison with embreyite. We assume that cassedanneite has structural similarity to embreyite with, presumably, a disordered distribution of Cr and V.

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.

scholarly journals How Nanoscale Dislocation Reactions Govern Low- Temperature and High-Stress Creep of Ni-Base Single Crystal Superalloys

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 134 ◽  
Author(s):  
David Bürger ◽  
Antonin Dlouhý ◽  
Kyosuke Yoshimi ◽  
Gunther Eggeler
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
High Stress ◽  
Shear Stresses ◽  
Creep Tests ◽  
Shear Creep ◽  
Tem Analysis ◽  
Transmission Electron ◽  
Crystallographic Shear ◽  
Shear System

The present work investigates γ-channel dislocation reactions, which govern low-temperature (T = 750 °C) and high-stress (resolved shear stress: 300 MPa) creep of Ni-base single crystal superalloys (SX). It is well known that two dislocation families with different b-vectors are required to form planar faults, which can shear the ordered γ’-phase. However, so far, no direct mechanical and microstructural evidence has been presented which clearly proves the importance of these reactions. In the mechanical part of the present work, we perform shear creep tests and we compare the deformation behavior of two macroscopic crystallographic shear systems [ 01 1 ¯ ] ( 111 ) and [ 11 2 ¯ ] ( 111 ) . These two shear systems share the same glide plane but differ in loading direction. The [ 11 2 ¯ ] ( 111 ) shear system, where the two dislocation families required to form a planar fault ribbon experience the same resolved shear stresses, deforms significantly faster than the [ 01 1 ¯ ] ( 111 ) shear system, where only one of the two required dislocation families is strongly promoted. Diffraction contrast transmission electron microscopy (TEM) analysis identifies the dislocation reactions, which rationalize this macroscopic behavior.

Unlocking the structure of mixed amorphous-crystalline ceramic oxide films synthesized under low temperature electromagnetic excitation

2017 ◽  
Vol 5 (35) ◽  
pp. 18434-18441 ◽  
Author(s):  
Nathan Nakamura ◽  
Maxwell W. Terban ◽  
Simon J. L. Billinge ◽  
B. Reeja-Jayan
Keyword(s):  
Distribution Function ◽  
Low Temperature ◽  
Electromagnetic Fields ◽  
Atomic Structure ◽  
Pair Distribution Function ◽  
Electromagnetic Excitation ◽  
X Ray ◽  
Ceramic Oxide ◽  
Pdf Analysis ◽  
Crystalline Ceramic

The effect of electromagnetic fields on nanoscale atomic structure was determined using synchrotron X-ray pair distribution function (PDF) analysis.

Structural properties of the thermoelectric material CuCrS2 and of deintercalated CuxCrS2 on different length scales: X-ray diffraction, pair distribution function and transmission electron microscopy studies

2017 ◽  
Vol 5 (36) ◽  
pp. 9331-9338 ◽  
Author(s):  
Anna-Lena Hansen ◽  
Torben Dankwort ◽  
Hendrik Groß ◽  
Martin Etter ◽  
Jan König ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Distribution Function ◽  
Structural Properties ◽  
Thermoelectric Materials ◽  
Pair Distribution Function ◽  
X Ray Diffraction ◽  
Length Scales ◽  
X Ray ◽  
Transmission Electron

Structural properties of the thermoelectric materials CuCrS2 and CuxCrS2 on different length scales.

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