A Combined IKL-ALCHEMI Technique for atom Configurations in Multinary Ordering Alloys and its Application to Cu-Au-Pd

1990 ◽  
Vol 48 (2) ◽  
pp. 488-489
Author(s):  
Syo Matsumura ◽  
Takao Moriraura ◽  
Kensuke Oki
Keyword(s):  
Binary Alloy ◽  
Structure Factor ◽  
Superlattice Reflection ◽  
Lattice Points ◽  
Atomic Configuration ◽  
Experimental Procedure ◽  
Pair Correlations ◽  
X Ray ◽  
Structure Factors ◽  
Independent Parameters

Diffraction technique of x ray, electron or neutron has been extensively utilized to determine atomic configuration in ordering alloys. The method of analysis has been well established for the binary alloy case. From the diffracted intensities or the values of structure factors, we can straightforwardly determine site-occupancies or pair-correlations of atoms on the fundamental lattice points in a binary alloy. For ternary or multinary alloys, however, it turns impossible to obtain the quantities concerning atomic configuration by the conventinal diffraction technique. This impossibility in the multinary case is due to the fact that the structure factor of a superlattice reflection is a function of two or more independent parameters describing the atomic configuration. In this paper we propose an experimental procedure to break through this impossibility; simultaneous employment of the Intersecting Kikuch-line (IKL) method and ALCKEMI (Atom Location by Channeling Enhanced Microanalysis) enables us to determine the occupation probabilities of constituent atoms on lattice sites in ternary or multinary ordering alloys.

X-Ray Investigations on Molten Cu-Sb Alloys

1994 ◽  
Vol 49 (4-5) ◽  
pp. 530-534 ◽  
Author(s):  
Th. Halm ◽  
H. Neumann ◽  
W. Hoyer
Keyword(s):  
Electronic Properties ◽  
Structure Factor ◽  
Correlation Functions ◽  
Pair Correlation ◽  
Model Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure Factors ◽  
Diffraction Structure ◽  
Eutectic Concentration

Abstract Using X-ray diffraction, structure factors and pair correlation functions of several molten Cu-Sb alloys and pure antimony were determined and compared with published structural, thermodynamic and electronic properties. The eutectic concentration Cu37Sb63 was investigated in dependence on temperature, and a model structure factor was calculated applying a segregation model.

X-ray Investigations of Liquid Bismuth-Copper Alloys

2000 ◽  
Vol 55 (3-4) ◽  
pp. 381-389 ◽  
Author(s):  
J. Nomssi Nzali ◽  
W. Hoyer
Keyword(s):  
Copper Alloys ◽  
X Ray Diffraction ◽  
Model Calculations ◽  
Experimental Procedure ◽  
X Ray ◽  
X Ray Scattering ◽  
Structure Factors ◽  
Reverse Monte Carlo Simulation ◽  
Square Well ◽  
Total Structure

Liquid copper, bismuth, and eleven bismuth-copper alloys were investigated at temperatures above the liquidus with X-ray diffraction. The experimental procedure was adjusted to reduce the effects of evaporation. The Faber-Ziman total structure factors S(Q) feature a splitting of the first maximum and negative values for Q around 1 Å -1 in a large concentration range. The results are compared to previous neutron diffraction results by Zaiss and Steeb, to square-well potential model calculations by Gopala Rao and Satpathy and to a simple segregation model. The segregation model reproduces the features qualitatively. Partial structure factors are assessed by fitting both neutron and X-ray scattering results with reverse Monte-Carlo simulation

Obtaining the structure factors for an epitaxial film using Cu X-ray radiation

2013 ◽  
Vol 46 (6) ◽  
pp. 1749-1754 ◽  
Author(s):  
P. Wadley ◽  
A. Crespi ◽  
J. Gázquez ◽  
M.A. Roldán ◽  
P. García ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thin Films ◽  
Structure Factor ◽  
Tetragonal Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Structure Factors ◽  
Scanning Transmission

Determining atomic positions in thin films by X-ray diffraction is, at present, a task reserved for synchrotron facilities. Here an experimental method is presented which enables the determination of the structure factor amplitudes of thin films using laboratory-based equipment (Cu Kα radiation). This method was tested using an epitaxial 130 nm film of CuMnAs grown on top of a GaAs substrate, which unlike the orthorhombic bulk phase forms a crystal structure with tetragonal symmetry. From the set of structure factor moduli obtained by applying this method, the solution and refinement of the crystal structure of the film has been possible. The results are supported by consistent high-resolution scanning transmission electron microscopy and stoichiometry analyses.

scholarly journals Partial structure factors derived from coarse-grained phase-separation dynamics on a disordered lattice with density fluctuations

2021 ◽  
Author(s):  
Puwadet Sutipanya ◽  
Takashi Arai
Keyword(s):  
Phase Separation ◽  
Structure Factor ◽  
Lattice Point ◽  
Local Density ◽  
Lattice Points ◽  
Concentration Fluctuations ◽  
Coarse Grained ◽  
Partial Structure ◽  
Disordered Lattice ◽  
Structure Factors

Abstract The simplest and most time-efficient phase-separation dynamics simulations are carried out on a disordered lattice to calculate the partial structure factors of coarse-grained A-B binary mixtures. The typical coarse-grained phase-separation models use regular lattices and can describe the local concentrations but cannot describe both local density and concentration fluctuations. To introduce fluctuation for local density in the model, the particle positions from a hard sphere fluid model are determined as disordered lattice points for the model. Then we place the local order parameter as the difference of the concentrations of A and B components on each lattice point. The concentration at each lattice point is time-evolved by discrete equations derived from the Cahn-Hilliard equation. From both fluctuations, Bhatia and Thornton’s structure factor can be accurately calculated. The structure factor for concentration fluctuations at the large wavenumber region gives us the correct mean concentrations of the components. Using the mean concentrations, partial structure factors can be converted from three of Bhatia and Thornton’s structure factors. The present model and procedures can provide a means of analysing the structural properties of many materials that exhibit complex morphological changes.

scholarly journals Beyond integration: modeling every pixel to obtain better structure factors from stills

IUCrJ ◽  
2020 ◽  
Vol 7 (6) ◽  
pp. 1151-1167 ◽  
Author(s):  
Derek Mendez ◽  
Robert Bolotovsky ◽  
Asmit Bhowmick ◽  
Aaron S. Brewster ◽  
Jan Kern ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Structure Factor ◽  
Reciprocal Lattice ◽  
Likelihood Estimation ◽  
Model Parameters ◽  
Reciprocal Lattice Point ◽  
X Ray ◽  
Novel Approach ◽  
Structure Factors ◽  
Ewald Sphere

Most crystallographic data processing methods use pixel integration. In serial femtosecond crystallography (SFX), the intricate interaction between the reciprocal lattice point and the Ewald sphere is integrated out by averaging symmetrically equivalent observations recorded across a large number (104−106) of exposures. Although sufficient for generating biological insights, this approach converges slowly, and using it to accurately measure anomalous differences has proved difficult. This report presents a novel approach for increasing the accuracy of structure factors obtained from SFX data. A physical model describing all observed pixels is defined to a degree of complexity such that it can decouple the various contributions to the pixel intensities. Model dependencies include lattice orientation, unit-cell dimensions, mosaic structure, incident photon spectra and structure factor amplitudes. Maximum likelihood estimation is used to optimize all model parameters. The application of prior knowledge that structure factor amplitudes are positive quantities is included in the form of a reparameterization. The method is tested using a synthesized SFX dataset of ytterbium(III) lysozyme, where each X-ray laser pulse energy is centered at 9034 eV. This energy is 100 eV above the Yb3+ L-III absorption edge, so the anomalous difference signal is stable at 10 electrons despite the inherent energy jitter of each femtosecond X-ray laser pulse. This work demonstrates that this approach allows the determination of anomalous structure factors with very high accuracy while requiring an order-of-magnitude fewer shots than conventional integration-based methods would require to achieve similar results.

HgH2 meets relativistic quantum crystallography. How to teach relativity to a non-relativistic wavefunction

2021 ◽  
Vol 77 (1) ◽  
pp. 54-66
Author(s):  
Michal Podhorský ◽  
Lukáš Bučinský ◽  
Dylan Jayatilaka ◽  
Simon Grabowsky
Keyword(s):  
Systematic Error ◽  
Structure Factor ◽  
Relativistic Quantum ◽  
Relativistic Effects ◽  
X Ray ◽  
Structure Factors ◽  
Quantum Crystallography

The capability of X-ray constrained wavefunction (XCW) fitting to introduce relativistic effects into a non-relativistic wavefunction is tested. It is quantified how much of the reference relativistic effects can be absorbed in the non-relativistic XCW calculation when fitted against relativistic structure factors of a model HgH2 molecule. Scaling of the structure-factor sets to improve the agreement statistics is found to introduce a significant systematic error into the XCW fitting of relativistic effects.

Measurement of small structure factors by the critical-voltage effect in HEED: The superlattice reflections in β'nial, β'CoAl and γtial

1992 ◽  
Vol 50 (2) ◽  
pp. 1174-1175
Author(s):  
Alan G. Fox ◽  
Mark A. Tabbernor
Keyword(s):  
Structure Factor ◽  
High Energy ◽  
Critical Voltage ◽  
Intermetallic Alloys ◽  
Rocking Curve ◽  
X Ray ◽  
Structure Factors ◽  
Factor Measurement ◽  
Small Structure ◽  
Convergent Beam

The systematic critical voltage effect, Vc, in high energy electron diffraction has been used for some time to accurately measure low-angle x-ray structure factor structure factor amplitudes (see e.g. 1). It has a significant advantage over other methods for accurate structure factor measurement, such as systematic convergent beam rocking curve or x-ray Pendellösung techniques, in that it is capable of measuring very small structure factors such as the 222 ‘forbidden’ reflections in Si and Ge (see e.g. 2). In the present work the potential of the systematic Vc method for measuring small structure factor amplitudes and average Debye-Waller factors in the intermetallic alloys NiAl, CoAl and TiAl will be demonstrated.The structure factors, F, for ordered stoichiometric B2 alloys comprising A and B atoms such as Ni (Co)Al are given by

Probing of Structure Factor of Water to 57 GPa and 1500 K

2006 ◽  
Vol 987 ◽  
Author(s):  
Alexander F. Goncharov ◽  
Chrystele Sanloup ◽  
Nir Goldman ◽  
Jonathan C. Crowhurst ◽  
Lawrence E. Fried ◽  
...  
Keyword(s):  
Structure Factor ◽  
Diamond Anvil Cell ◽  
Melting Line ◽  
X Ray ◽  
Structure Factors ◽  
Diamond Anvil ◽  
Laser Heated ◽  
Density Of Water ◽  
Monochromatic Synchrotron ◽  
Good Agreement

AbstractThe x-ray structure factor of water has been measured along the melting line to 57 GPa and 1500 K using focused monochromatic synchrotron radiation and laser heated diamond anvil cell. The oxygen radial distribution function, g(r) is determined from these data. We have also calculated g(r) using ab initio methods and find a good agreement with the experiment. Based of the similarity of the measured and calculated structure factors determined density of water under extreme conditions unattainable previously.

X-ray Diffraction Study of Molten Te and Tl-Te Alloys

1975 ◽  
Vol 30 (12) ◽  
pp. 1655-1660 ◽  
Author(s):  
Y. Waseda ◽  
S. Tamaki
Keyword(s):  
Structure Factor ◽  
Molten Metals ◽  
X Ray Diffraction ◽  
Partial Structure ◽  
X Ray ◽  
Partial Structures ◽  
Structure Factors ◽  
Diffraction Patterns ◽  
Total Structure ◽  
Constituent Elements

Abstract X-ray diffraction patterns have been obtained from molten Te at 470, 520 and 570 °C. The heights of the peak maxima in the structure factor were much the same in contrast with those of typical molten metals such as sodium.Molten Tl-Te alloys have been studied by X-ray diffraction for the alloy compositions 25, 33.3, 50, 60 and 75 at% Te at 500 °C and at about 20 °C above the liquidus. The total structure factors for the 25 and 33.3 at% Te alloys were almost the same as that of pure Tl. This implies that the atomic arrangement of these molten alloys is very close to that of pure Tl. Although a drastic change is not found in the general form of the structure factor, the parameter of the range of local atomic order abruptly increases on passing from Tl2Te to more Te-rich alloys. The three partial structures were also evaluated from the observed X-ray intensities assuming that each partial structure is independent of the relative abundance of the constituent elements in the alloys.

Structure of Mn-Si-Melts by Means of X-Ray Diffraction

1983 ◽  
Vol 38 (10) ◽  
pp. 1093-1097 ◽  
Author(s):  
E. Nassif ◽  
P. Lamparter ◽  
B. Sedelmeyer ◽  
S. Steeb
Keyword(s):  
Structure Factor ◽  
Melt Spinning ◽  
Pair Correlation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Coordination Numbers ◽  
Glass Forming ◽  
Structure Factors ◽  
Total Structure Factor ◽  
Total Structure

Abstract The binary molten alloys Mn74Si26 and Mn33.5Si66.5 have been investigated by means of X-ray diffraction. The total structure factors as well as the total pair correlation functions were evaluated. The interatomic distances and total coordination numbers are given. The structural results for Mn74Si26 were compared to those for amorphous Mn74Si23P3 and for a tetrahedral packing model. A pronounced shoulder on the second maximum of the structure factor, which normally is characteristic for the curves obtained with amorphous substances was observed for the Mn74Si26 melt. With the Mn33.5Si66.5 melt, however, this feature cold not be observed. Since with this concentration no glass forming by melt spinning is possible, a correlation between the shape of the second maximum of a total structure factor and the glass forming ability of the corresponding melt is suggested.

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