scholarly journals Size and spatial correlation of defective domains in yttrium-doped CeO2

2015 ◽  
Vol 30 (S1) ◽  
pp. S119-S126 ◽  
Author(s):  
Stefano Checchia ◽  
Marco Scavini ◽  
Mattia Allieta ◽  
Michela Brunelli ◽  
Claudio Ferrero ◽  
...  
Keyword(s):  
Distribution Function ◽  
High Resolution ◽  
Pair Distribution Function ◽  
Structural Models ◽  
Resolution Function ◽  
Reliable Model ◽  
Close Relationship ◽  
Instrumental Resolution ◽  
Doped Ceo2 ◽  
Low Symmetry

The size of dopant-rich nanodomains was assessed in four samples of Ce1−μYμO2−μ/2 through systematic pair distribution function (PDF) refinements. Experimental G(r) curves were fitted by different structural models with the aim of finding a description which balanced precise structure parameterization and reasonable number of parameters. The most reliable model was a single Y2O3-like phase, which best accommodated to the close relationship between the fluorite (CeO2-like) and C-type (Y2O3-like) structures. In this model, a refined cation coordinate, x(M2), measured the relative occurrence in the G(r) of the chemical environment of Y and Ce at any value of r. The r-value at which x(M2) vanished, i.e. at which the refined C-type cell becomes a redundant, low-symmetry description of a fluorite cell, was assumed as the size of a C-type domain. Subtle features in G(r) could be attributed to the fluorite or C-type phase up to ~500 Å thanks to the narrow instrumental resolution function of the ID31 beamline (now ID22) at the ESRF, which allows us to get high resolution PDF data.

Determination ofB-cation chemical short-range order in perovskites from the total pair-distribution function

2008 ◽  
Vol 41 (2) ◽  
pp. 386-392 ◽  
Author(s):  
Victor Krayzman ◽  
Igor Levin
Keyword(s):  
Distribution Function ◽  
Pair Distribution Function ◽  
Short Range ◽  
Short Range Order ◽  
Structural Models ◽  
Range Order ◽  
Cation Order ◽  
Powder Samples ◽  
Complex Perovskites

Short-rangeB-cation order affects the functional properties of many complex perovskites. However, current ability to measure the characteristics of such chemical short-range order (SRO) in perovskite-structured ceramics is limited. In the present study, two distinct methods are compared for the determination of theB-cation SRO parameters from the total scattering pair-distribution function (PDF). Both methods rely on reverse Monte Carlo refinements of the structural models but differ in the procedures used to extract the SRO characteristics. The accuracy of these methods was tested using synthetic PDF data generated for models of prototype Ca(Zr,Ti)O3solid solutions. One of the approaches developed in the present study, which proved to yield the most accurate results, was used to analyze the SRO of Ti and Zr in powder samples of Ca(Zr,Ti)O3.

scholarly journals Local structure of In0.5Ga0.5As from joint high-resolution and differential pair distribution function analysis

2000 ◽  
Vol 88 (2) ◽  
pp. 665-672 ◽  
Author(s):  
V. Petkov ◽  
I.-K. Jeong ◽  
F. Mohiuddin-Jacobs ◽  
Th. Proffen ◽  
S. J. L. Billinge ◽  
...  
Keyword(s):  
Distribution Function ◽  
High Resolution ◽  
Local Structure ◽  
Pair Distribution Function ◽  
Function Analysis ◽  
Differential Pair

PDF analysis of ferrihydrite and the violation of Pauling's Principia

Clay Minerals ◽  
2010 ◽  
Vol 45 (2) ◽  
pp. 225-228 ◽  
Author(s):  
A. Manceau
Keyword(s):  
Distribution Function ◽  
Neutron Diffraction ◽  
Regression Models ◽  
Pair Distribution Function ◽  
Structural Models ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ferric Oxyhydroxide ◽  
Pdf Analysis ◽  
Crystal Electron

AbstractThe risk of overfitting pair distribution function (PDF) data for highly defective material (Farrow et al., 2007) is illuminated with the example of the nanocrystalline hydrous ferric oxyhydroxide, ferrihydrite. Two structural models have been published by Michel et al. (2007, 2010) using this method, both of which contradict the standard ‘ferrihydrits’ model established by X-ray diffraction (Drits et al., 1993), and confirmed by single-crystal electron nanodiffraction (Janney et al., 2001) and neutron diffraction (Jansen et al., 2002). Although PDF data are reproduced equally well with the two regression models, neither model is realistic: the first (fhyd6) violates Pauling's 2nd rule, and the second (ferrifh), Pauling's 3rd rule.

scholarly journals Study of the Microstructure of Amorphous Silica Nanostructures Using High-Resolution Electron Microscopy, Electron Energy Loss Spectroscopy, X-ray Powder Diffraction, and Electron Pair Distribution Function

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4393 ◽  
Author(s):  
Lahcen Khouchaf ◽  
Khalid Boulahya ◽  
Partha Pratim Das ◽  
Stavros Nicolopoulos ◽  
Viktória Kovács Kis ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Distribution Function ◽  
High Resolution ◽  
Amorphous Silica ◽  
Pair Distribution Function ◽  
Electron Pair ◽  
Reaction Times ◽  
X Ray ◽  
Silica Nanostructures ◽  
Electron Energy Loss

Silica has many industrial (i.e., glass formers) and scientific applications. The understanding and prediction of the interesting properties of such materials are dependent on the knowledge of detailed atomic structures. In this work, amorphous silica subjected to an accelerated alkali silica reaction (ASR) was recorded at different time intervals so as to follow the evolution of the structure by means of high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and electron pair distribution function (e-PDF), combined with X-ray powder diffraction (XRPD). An increase in the size of the amorphous silica nanostructures and nanopores was observed by HRTEM, which was accompanied by the possible formation of Si–OH surface species. All of the studied samples were found to be amorphous, as observed by HRTEM, a fact that was also confirmed by XRPD and e-PDF analysis. A broad diffuse peak observed in the XRPD pattern showed a shift toward higher angles following the higher reaction times of the ASR-treated material. A comparison of the EELS spectra revealed varying spectral features in the peak edges with different reaction times due to the interaction evolution between oxygen and the silicon and OH ions. Solid-state nuclear magnetic resonance (NMR) was also used to elucidate the silica nanostructures.

Pair distribution function analysis of molecular compounds: significance and modeling approach discussed using the example ofp-terphenyl

2012 ◽  
Vol 45 (3) ◽  
pp. 482-488 ◽  
Author(s):  
Nadine Rademacher ◽  
Luke L. Daemen ◽  
Eric L. Chronister ◽  
Thomas Proffen
Keyword(s):  
Distribution Function ◽  
Pair Distribution Function ◽  
Short Range ◽  
Short Range Order ◽  
Function Analysis ◽  
Structural Models ◽  
Range Order ◽  
Molecular Systems ◽  
The Common ◽  
Molecular Compounds

Modeling the pair distribution function (PDF) of molecular compounds is a challenging task because intra- and intermolecular interactions lead to very different features in the PDF. This article discusses the different peak shapes in PDFs of molecular compounds in detail. Moreover, the common methods to calculate PDFs from structural models are summarized and evaluated with respect to molecular systems and an approach to calculate PDFs from molecular crystals more accurately is introduced.p-Terphenyl was chosen as a test compound. It adopts a crystal structure with disordered features and short-range order. The short-range order was previously investigated by analyzing single-crystal diffuse scattering and it was also extracted from experimental PDFs during this study.

scholarly journals Exact and fast calculation of the X-ray pair distribution function

2020 ◽  
Vol 53 (3) ◽  
pp. 710-721
Author(s):  
Reinhard B. Neder ◽  
Thomas Proffen
Keyword(s):  
Distribution Function ◽  
Pair Distribution Function ◽  
Periodic Structures ◽  
Form Factors ◽  
Exact Algorithm ◽  
Magnetic Scattering ◽  
Primary Data ◽  
X Ray ◽  
Conventional Calculation ◽  
Instrumental Resolution

A fast and exact algorithm to calculate the powder pair distribution function (PDF) for the case of periodic structures is presented. The new algorithm calculates the PDF by a detour via reciprocal space. The calculated normalized total powder diffraction pattern is transferred into the PDF via the sine Fourier transform. The calculation of the PDF via the powder pattern avoids the conventional simplification of X-ray and electron atomic form factors. It is thus exact for these types of radiation, as is the conventional calculation for the case of neutron diffraction. The new algorithm further improves the calculation speed. Additional advantages are the improved detection of errors in the primary data, the handling of preferred orientation, the ease of treatment of magnetic scattering and a large improvement to accommodate more complex instrumental resolution functions.

High-Resolution Cryo-Electron Microscopy of Biological Macromolecules

1990 ◽  
Vol 48 (1) ◽  
pp. 126-127
Author(s):  
Yoshinori Fujiyoshi
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Diffraction Pattern ◽  
Superfluid Helium ◽  
Copper Phthalocyanine ◽  
Optical Diffraction ◽  
Irradiation Damage ◽  
Biological Macromolecules ◽  
Cross Sectional ◽  
Instrumental Resolution

The resolution of direct images of biological macromolecules is normally restricted to far less than 0.3 nm. This is not due instrumental resolution, but irradiation damage. The damage to biological macromolecules may expect to be reduced when they are cooled to a very low temperature. We started to develop a new cryo-stage for a high resolution electron microscopy in 1983, and successfully constructed a superfluid helium stage for a 400 kV microscope by 1986, whereby chlorinated copper-phthalocyanine could be photographed to a resolution of 0.26 nm at a stage temperature of 1.5 K. We are continuing to develop the cryo-microscope and have developed a cryo-microscope equipped with a superfluid helium stage and new cryo-transfer device.The New cryo-microscope achieves not only improved resolution but also increased operational ease. The construction of the new super-fluid helium stage is shown in Fig. 1, where the cross sectional structure is shown parallel to an electron beam path. The capacities of LN2 tank, LHe tank and the pot are 1400 ml, 1200 ml and 3 ml, respectively. Their surfaces are placed with gold to minimize thermal radiation. Consumption rates of liquid nitrogen and liquid helium are 170 ml/hour and 140 ml/hour, respectively. The working time of this stage is more than 7 hours starting from full LN2 and LHe tanks. Instrumental resolution of our cryo-stage cooled to 4.2 K was confirmed to be 0.20 nm by an optical diffraction pattern from the image of a chlorinated copper-phthalocyanine crystal. The image and the optical diffraction pattern are shown in Fig. 2 a, b, respectively.

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