Positioning errors during stepped scans in X-ray crystallography

2008 ◽  
Vol 41 (4) ◽  
pp. 768-775 ◽  
Author(s):  
Roman Shayduk ◽  
Wolfgang Braun
Keyword(s):  
Data Acquisition ◽  
Grazing Incidence ◽  
Reciprocal Space ◽  
Continuous Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Positioning Errors ◽  
Data Points ◽  
Motor Movements ◽  
The Ideal

It is demonstrated that many X-ray measurements, especially at grazing incidence, allow continuous data acquisition during stepped scans without deadtime for diffractometer motor motions. Analyzing the deviation from the ideal trajectory during independent motor movements, it is found that the deviation from the direct line connecting two data points in reciprocal space is very small for large volumes of reciprocal space. A synchronization algorithm to determine coordinated motor movements that follow the direct line connecting the data points is presented. Verification experiments on a six-circle diffractometer demonstrate the validity of the approach.

Epitaxial Ni nanoparticles on CaF2(001), (110) and (111) surfaces studied by three-dimensional RHEED, GIXD and GISAXS reciprocal-space mapping techniques

2017 ◽  
Vol 50 (3) ◽  
pp. 830-839 ◽  
Author(s):  
S. M. Suturin ◽  
V. V. Fedorov ◽  
A. M. Korovin ◽  
N. S. Sokolov ◽  
A. V. Nashchekin ◽  
...  
Keyword(s):  
Lattice Structure ◽  
Three Dimensional ◽  
Grazing Incidence ◽  
High Energy ◽  
Reciprocal Space ◽  
Mapping Technique ◽  
Face Centered Cubic ◽  
X Ray ◽  
Cubic Lattice ◽  
Face Centered

The development of growth techniques aimed at the fabrication of nanoscale heterostructures with layers of ferroic 3dmetals on semiconductor substrates is very important for their potential usage in magnetic media recording applications. A structural study is presented of single-crystal nickel island ensembles grown epitaxially on top of CaF2/Si insulator-on-semiconductor heteroepitaxial substrates with (111), (110) and (001) fluorite surface orientations. The CaF2buffer layer in the studied multilayer system prevents the formation of nickel silicide, guides the nucleation of nickel islands and serves as an insulating layer in a potential tunneling spin injection device. The present study, employing both direct-space and reciprocal-space techniques, is a continuation of earlier research on ferromagnetic 3dtransition metals grown epitaxially on non-magnetic and magnetically ordered fluorides. It is demonstrated that arrays of stand-alone faceted nickel islands with a face-centered cubic lattice can be grown controllably on CaF2surfaces of (111), (110) and (001) orientations. The proposed two-stage nickel growth technique employs deposition of a thin seeding layer at low temperature followed by formation of the islands at high temperature. The application of an advanced three-dimensional mapping technique exploiting reflection high-energy electron diffraction (RHEED) has proved that the nickel islands tend to inherit the lattice orientation of the underlying fluorite layer, though they exhibit a certain amount of {111} twinning. As shown by scanning electron microscopy, grazing-incidence X-ray diffraction (GIXD) and grazing-incidence small-angle X-ray scattering (GISAXS), the islands are of similar shape, being faceted with {111} and {100} planes. The results obtained are compared with those from earlier studies of Co/CaF2epitaxial nanoparticles, with special attention paid to the peculiarities related to the differences in lattice structure of the deposited metals: the dual-phase hexagonal close-packed/face-centered cubic lattice structure of cobalt as opposed to the single-phase face-centered cubic lattice structure of nickel.

scholarly journals Improved data acquisition in grazing-incidence X-ray scattering experiments using a pixel detector

2005 ◽  
Vol 61 (4) ◽  
pp. 418-425 ◽  
Author(s):  
C. M. Schlepütz ◽  
R. Herger ◽  
P. R. Willmott ◽  
B. D. Patterson ◽  
O. Bunk ◽  
...  
Keyword(s):  
Data Acquisition ◽  
Grazing Incidence ◽  
Pixel Detector ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

scholarly journals Unwarping GISAXS data

IUCrJ ◽  
2018 ◽  
Vol 5 (6) ◽  
pp. 737-752 ◽  
Author(s):  
Jiliang Liu ◽  
Kevin G. Yager
Keyword(s):  
Born Approximation ◽  
Grazing Incidence ◽  
Initial Guess ◽  
Reciprocal Space ◽  
Scattering Data ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
X Ray ◽  
X Ray Scattering ◽  
Transmission And Reflection

Grazing-incidence small-angle X-ray scattering (GISAXS) is a powerful technique for measuring the nanostructure of coatings and thin films. However, GISAXS data are plagued by distortions that complicate data analysis. The detector image is a warped representation of reciprocal space because of refraction, and overlapping scattering patterns appear because of reflection. A method is presented to unwarp GISAXS data, recovering an estimate of the true undistorted scattering pattern. The method consists of first generating a guess for the structure of the reciprocal-space scattering by solving for a mutually consistent prediction from the transmission and reflection sub-components. This initial guess is then iteratively refined by fitting experimental GISAXS images at multiple incident angles, using the distorted-wave Born approximation (DWBA) to convert between reciprocal space and detector space. This method converges to a high-quality reconstruction for the undistorted scattering, as validated by comparing with grazing-transmission scattering data. This new method for unwarping GISAXS images will broaden the applicability of grazing-incidence techniques, allowing experimenters to inspect undistorted visualizations of their data and allowing a broader range of analysis methods to be applied to GI data.

scholarly journals Non-equilibrium phonon dynamics studied by grazing-incidence femtosecond X-ray crystallography

2010 ◽  
Vol 66 (2) ◽  
pp. 157-167 ◽  
Author(s):  
S. L. Johnson ◽  
P. Beaud ◽  
E. Vorobeva ◽  
C. J. Milne ◽  
É. D. Murray ◽  
...  
Keyword(s):  
Structural Changes ◽  
Near Infrared ◽  
Lattice Strain ◽  
Reciprocal Lattice ◽  
Grazing Incidence ◽  
Quantitative Information ◽  
Lattice Vector ◽  
X Ray ◽  
X Ray Crystallography ◽  
Carrier Energy

The timescales for structural changes in a single crystal of bismuth after excitation with an intense near-infrared laser pulse are studied with femtosecond pump-probe X-ray diffraction. Changes in the intensity and reciprocal-lattice vector of several reflections give quantitative information on the structure factor and lattice strain as a function of time, with a resolution of 200 fs. The results indicate that the majority of excess carrier energy that remains near the surface is transferred to vibrational modes on a timescale of about 10 ps, and that the resultant increase in the variance of the atomic positions at these times is consistent with the overall magnitude of lattice strain that develops.

scholarly journals [Dicyclohexyl(sulfanylidene)-λ5-phosphanyl]methanol

Molbank ◽  
10.3390/m1069 ◽  
2019 ◽  
Vol 2019 (3) ◽  
pp. M1069
Author(s):  
William Henderson ◽  
Obinna Okpareke ◽  
Ainnul Azizan ◽  
Edward Tiekink
Keyword(s):  
Mass Spectrometry ◽  
Hydrogen Bonds ◽  
Phosphorus Atom ◽  
Elemental Sulfur ◽  
2D Nmr ◽  
X Ray ◽  
X Ray Crystallography ◽  
Molar Equivalent ◽  
Esi Mass Spectrometry ◽  
The Ideal

The title compound, [dicyclohexyl(sulfanylidene)-λ5-phosphanyl]methanol, Cy2P(=S)CH2OH (1), was obtained from the reaction between [Cy2P(CH2OH)2]Cl with one molar equivalent of NaOH and an excess of elemental sulfur (powdered). Characterization was by a single-crystal X-ray structure determination as well as IR, and 1D-NMR (1H, 13C{1H}, 31P{1H}), and 2D-NMR (DEPT-135 and HSQC) spectroscopy, ESI mass spectrometry, and elemental analysis. X-ray crystallography on Compound 1 shows the phosphorus atom to be tetrahedrally coordinated within a non-symmetric C3S donor set but with relatively minor distortions from the ideal geometry. In the molecular packing, hydroxyl-O–H⋯S(thione) hydrogen bonds led to supramolecular helical chains along the b-axis direction.

scholarly journals On effective and optical resolutions of diffraction data sets

2013 ◽  
Vol 69 (10) ◽  
pp. 1921-1934 ◽  
Author(s):  
Ludmila Urzhumtseva ◽  
Bruno Klaholz ◽  
Alexandre Urzhumtsev
Keyword(s):  
Diffraction Data ◽  
Minimum Distance ◽  
Optical Resolution ◽  
General Interest ◽  
Data Sets ◽  
Accurate Calculation ◽  
Data Set ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Ideal

In macromolecular X-ray crystallography, diffraction data sets are traditionally characterized by the highest resolutiondhighof the reflections that they contain. This measure is sensitive to individual reflections and does not refer to the eventual data incompleteness and anisotropy; it therefore does not describe the data well. A physically relevant and robust measure that provides a universal way to define the `actual' effective resolutiondeffof a data set is introduced. This measure is based on the accurate calculation of the minimum distance between two immobile point scatterers resolved as separate peaks in the Fourier map calculated with a given set of reflections. This measure is applicable to any data set, whether complete or incomplete. It also allows characterizion of the anisotropy of diffraction data sets in whichdeffstrongly depends on the direction. Describing mathematical objects, the effective resolutiondeffcharacterizes the `geometry' of the set of measured reflections and is irrelevant to the diffraction intensities. At the same time, the diffraction intensities reflect the composition of the structure from physical entities: the atoms. The minimum distance for the atoms typical of a given structure is a measure that is different from and complementary todeff; it is also a characteristic that is complementary to conventional measures of the data-set quality. Following the previously introduced terms, this value is called the optical resolution,dopt. The optical resolution as defined here describes the separation of the atomic images in the `ideal' crystallographic Fourier map that would be calculated if the exact phases were known. The effective and optical resolution, as formally introduced in this work, are of general interest, giving a common `ruler' for all kinds of crystallographic diffraction data sets.

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