scholarly journals Static Displacements of Atoms in Crystalline Metallic Solid Solutions

1994 ◽  
Vol 375 ◽  
Author(s):  
Cullie Sparks ◽  
Gene Ice ◽  
Xiaogang Jiang ◽  
Paul Zschack
Keyword(s):  
Solid Solutions ◽  
Diffuse Scattering ◽  
Nearest Neighbor ◽  
Near Neighbor ◽  
Crystalline Solid ◽  
X Ray ◽  
Lattice Constants ◽  
Atomic Displacements ◽  
X Ray Scattering ◽  
Individual Bond

AbstractMeasurement of diffuse x-ray scattering from binary crystalline solid solutions at more than one x-ray energy is a sensitive probe of the average interatomic distance between neighboring pairs of atoms. Deviations of these bond distances by as little as 0.001Å are easily detected in the diffuse scattering from binary alloys consisting of atoms nearby in the periodic table and/or where x-ray energies chosen near their absorption edges can change the scattering contrast. Individual bond distances (AA, AB and BB) are recovered out to several near neighbor shells by combining three scattering measurements at x-ray energies chosen for maximum and minimum contrast. Average bond distances recovered from four metal alloys Fe77.5Ni22.5, Fe46.5Ni53.5Cr47Fe53and Cr20Ni80 are discussed. We find that the interatomic distances measured for these alloys give interesting insights to atomic displacements in solid solutions. Nearest neighbor bond distances are not well represented by phenomenological models based on pure element atomic size and concentration dependence of the lattice constants. Radial and nonradial displacements are recovered from these measurements of diffuse scattering.

scholarly journals Static Atomic Displacements in Crystalline Solid Solution Alloys

1996 ◽  
Vol 437 ◽  
Author(s):  
Gene Ice ◽  
Cullie Sparks ◽  
J. Lee Robertson ◽  
J. Ernest Epperson ◽  
Xiaogang Jiang
Keyword(s):  
Synchrotron Radiation ◽  
Crystalline Solid ◽  
Local Order ◽  
Chemical Order ◽  
X Ray ◽  
Atomic Displacements ◽  
X Ray Scattering ◽  
New Information ◽  
Z Contrast

AbstractAtom size differences induce static displacements from an average alloy lattice and play an important role in controlling alloy phase stability and properties. The details of this role however, are difficult to study; chemical order and displacements are strongly interrelated and static displacements are hard to measure. Diffuse x-ray scattering measurements with tunable-synchrotron radiation can now measure element-specific static displacements with an accuracy of ± 0.1 pm and can simultaneously measure local chemical order out to 20 shells or more. Ideal alloys for diffuse scattering analysis with synchrotron radiation, are those that have previously been the most intractable: alloys with small Z contrast, alloys with only local order and alloys with small size differences. The combination of precise characterization of local chemical order and precise measurement of static displacement provides new information that challenges existing alloy models. We report on an ongoing systematic study of static displacements in the Fe/Ni/Cr alloys and compare the observed static displacements to the static displacements predicted by current theories. The availability of more brilliant 3rd generation hard x-ray sources will greatly enhance these measurements.

A study of the local atomic structure in Hg0.80Cd0.20Te using x-ray diffuse scattering

1993 ◽  
Vol 8 (4) ◽  
pp. 855-863 ◽  
Author(s):  
J.P. Quintana ◽  
J.B. Cohen
Keyword(s):  
Diffuse Scattering ◽  
Volume Measurement ◽  
Lattice Parameter ◽  
Near Neighbor ◽  
Cation Sublattice ◽  
Thermal Diffuse Scattering ◽  
X Ray ◽  
X Ray Scattering ◽  
The Difference ◽  
Thermal Diffuse

The local atomic arrangements in a commercial n-type wafer of Hg0.8Cd0.8Te were investigated by measuring the diffuse x-ray scattering in two volumes in reciprocal space. A change in contrast between the two measurements was achieved by making one volume measurement at 12037 eV and a second volume measurement at 12270 eV, i.e., near the HgLIII edge. The difference between these two measurements yielded intensity only due to Hg–Hg, Hg–Te, and Hg–Cd pair interactions. In all three patterns, peak-like features were apparent at the forbidden Bragg peak positions on thermal diffuse scattering ridges that joined major Bragg reflections; these are primarily attributed to second order displacement effects on the mixed cation sublattice. The first two Warren–Cowley short-range order parameters were determined to be α½½0 = −0.050(26) and α110 = 0.118(35). Simulations of the structure revealed small ordered regions with a preference for 3:1 Hg–Cd near-neighbor configurations. The near-neighbor Hg–Te bonds contract from that calculated from the average crystal's lattice parameter, and this Hg–Te distance is less than the distance in HgTe.

Evolution of Interfacial Roughness Correlations of Fe Au Films Grown on Mgo(001) Substrates

1996 ◽  
Vol 440 ◽  
Author(s):  
P. C. Chow ◽  
R. Paniago ◽  
R. Forrest ◽  
S. C. Moss ◽  
S. S. P. Parkin ◽  
...  
Keyword(s):  
Thin Films ◽  
Diffuse Scattering ◽  
Perfect Match ◽  
Grazing Incidence ◽  
Interface Roughness ◽  
Metallic Structures ◽  
X Ray ◽  
Dimensional Image ◽  
X Ray Scattering ◽  
Image Plate Detector

AbstractThe growth by sputtering of a series of thin films of Fe/Au on MgO(001) substrates was analyzed using Bragg and diffuse X-ray scattering. The Fe (bcc) layer grows rotated by 45° with respect to the MgO – Au(fcc) (001) epitaxial orientation, resulting in an almost perfect match between the two metallic structures. By collecting the X-ray diffuse scattering under grazing incidence using a 2-dimensional image plate detector, we mapped the reciprocal space of these films. We characterized the correlated interface roughness starting with a buffer of Fe in which only three interfaces are present. The propagation of the roughness was subsequently characterized for Fe/Au multilayers with 40 and 100 bilayers. We observe an enlargement of the surface features as a function of time, evidenced by the longer lateral cutoff length measured for thicker films.

X-ray scattering effects of ionic size in solid solutions KCl–KBr

1970 ◽  
Vol 3 (5) ◽  
pp. 385-388 ◽  
Author(s):  
P. Luova ◽  
P. Tuominen ◽  
P. Vanha-Kämppä
Keyword(s):  
Solid Solutions ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Effects ◽  
Ionic Size ◽  
Ray Scattering

Diffuse X-ray scattering from tiny sample volumes

2005 ◽  
Vol 220 (12) ◽  
Author(s):  
Gene E. Ice ◽  
Rozaliya I. Barabash ◽  
Wenjun Liu
Keyword(s):  
Local Structure ◽  
Diffuse Scattering ◽  
High Performance ◽  
Sensitive Area ◽  
X Ray ◽  
X Ray Scattering ◽  
Defect Content ◽  
Ray Scattering

AbstractThe emergence of intense synchrotron X-ray sources, efficient focusing optics and high-performance X-ray sensitive area detectors allows for measurements of diffuse scattering from cubic micron-scale sample vol umes. Here we present an experiment that illustrates methods for studying the local structure and defect content of tiny sample volumes. In the experiment, an X-ray microbeam illuminating about ∼5 μm

scholarly journals Predicting X-ray diffuse scattering from translation–libration–screw structural ensembles

2015 ◽  
Vol 71 (8) ◽  
pp. 1657-1667 ◽  
Author(s):  
Andrew H. Van Benschoten ◽  
Pavel V. Afonine ◽  
Thomas C. Terwilliger ◽  
Michael E. Wall ◽  
Colin J. Jackson ◽  
...  
Keyword(s):  
Diffuse Scattering ◽  
Positional Distribution ◽  
Data Bank ◽  
Bragg Diffraction ◽  
Structural Refinement ◽  
X Ray ◽  
X Ray Crystallography ◽  
Atomic Displacements ◽  
Technological Advances ◽  
Structural Ensembles

Identifying the intramolecular motions of proteins and nucleic acids is a major challenge in macromolecular X-ray crystallography. Because Bragg diffraction describes the average positional distribution of crystalline atoms with imperfect precision, the resulting electron density can be compatible with multiple models of motion. Diffuse X-ray scattering can reduce this degeneracy by reporting on correlated atomic displacements. Although recent technological advances are increasing the potential to accurately measure diffuse scattering, computational modeling and validation tools are still needed to quantify the agreement between experimental data and different parameterizations of crystalline disorder. A new tool,phenix.diffuse, addresses this need by employing Guinier's equation to calculate diffuse scattering from Protein Data Bank (PDB)-formatted structural ensembles. As an example case,phenix.diffuseis applied to translation–libration–screw (TLS) refinement, which models rigid-body displacement for segments of the macromolecule. To enable the calculation of diffuse scattering from TLS-refined structures,phenix.tls_as_xyzbuilds multi-model PDB files that sample the underlying T, L and S tensors. In the glycerophosphodiesterase GpdQ, alternative TLS-group partitioning and different motional correlations between groups yield markedly dissimilar diffuse scattering maps with distinct implications for molecular mechanism and allostery. These methods demonstrate how, in principle, X-ray diffuse scattering could extend macromolecular structural refinement, validation and analysis.

Diffuse x-ray scattering from InGaAs/GaAs quantum dots

2003 ◽  
Vol 799 ◽  
Author(s):  
Rolf Köhler ◽  
Daniil Grigoriev ◽  
Michael Hanke ◽  
Martin Schmidbauer ◽  
Peter Schäfer ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Synchrotron Radiation ◽  
Diffuse Scattering ◽  
Data Evaluation ◽  
X Ray ◽  
X Ray Scattering ◽  
Gaas Matrix ◽  
Wetting Layers ◽  
Ray Scattering

ABSTRACTMulti-fold stacks of In0.6Ga0.4As quantum dots embedded into a GaAs matrix were investigated by means of x-ray diffuse scattering. The measurements were done with synchrotron radiation using different diffraction geometries. Data evaluation was based on comparison with simulated distributions of x-ray diffuse scattering. For the samples under consideration ((001) surface) there is no difference in dot extension along [110] and [-110] and no directional ordering. The measurements easily allow the determination of the average indium amount in the wetting layers. Data evaluation by simulation of x-ray diffuse scattering gives an increase of Incontent from the dot bottom to the dot top.

A High-Energy Monochromatic Laue (MonoLaue) X-ray Diffuse Scattering Study of KMnF3 using an Image Plate

1997 ◽  
Vol 30 (1) ◽  
pp. 16-20 ◽  
Author(s):  
A. Gibaud ◽  
D. Harlow ◽  
J. B. Hastings ◽  
J. P. Hill ◽  
D. Chapman
Keyword(s):  
Diffuse Scattering ◽  
High Energy ◽  
Experimental Conditions ◽  
X Ray ◽  
Image Plate ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Diffraction Patterns ◽  
Ray Scattering

The technique of high-energy monochromatic Laue X-ray scattering using image plates to record the diffraction patterns is presented. A tunable wiggler beamline is used as an X-ray source. It is shown that such experimental conditions present many advantages over conventional tube sources and photographic films. A study of diffuse scattering in the perovskite compound KMnF3 is presented to illustrate this in a qualitative way.

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