Indexing, Extraction of Integrated Intensity, and Structure Solution by the Direct Method and Charge Flipping from Power X-Ray Diffraction Data

AbstractThe structure of a 2-chain helical form of sulphur with 9 atoms per unit-cell has been determined from powder synchrotron x-ray diffraction data obtained at 3 GPa and 400ºC, using a combination of global optimization, simulated annealing and Rietveld refinement techniques. Final refinement of the structure in trigonal space group

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Advantages of a Redefinition of Variable-Space in Direct-Space Structure Solution from Powder X-Ray Diffraction Data

ChemPhysChem ◽

10.1002/cphc.200600726 ◽

2007 ◽

Vol 8 (5) ◽

pp. 650-653 ◽

Cited By ~ 12

Author(s):

Zhongfu Zhou ◽

Veronique Siegler ◽

Eugene Y. Cheung ◽

Scott Habershon ◽

Kenneth D. M. Harris ◽

...

Keyword(s):

Diffraction Data ◽

Space Structure ◽

X Ray Diffraction ◽

X Ray ◽

Structure Solution ◽

Variable Space

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The direct determination of X-ray diffraction data from specific depths

Powder Diffraction ◽

10.1154/1.1913707 ◽

2005 ◽

Vol 20 (3) ◽

pp. 233-240

Author(s):

A. Broadhurst ◽

K. D. Rogers ◽

D. W. Lane ◽

T. W. Lowe

Keyword(s):

Diffraction Data ◽

Direct Method ◽

Direct Determination ◽

Simulated Data ◽

X Ray Diffraction ◽

Linear Absorption ◽

X Ray ◽

Measured Angle ◽

Data Collections

A direct method for determining powder diffraction data from a range of depths is described, where the linear absorption coefficient may vary with depth. A series of traditional data collections with varying angles of incidence are required, and the X-ray diffraction data arising from specific depths will be calculated by the transformation of these measured, angle-dependent spectra. These may then be analysed using any conventional method in order to gain information about characteristics of the sample in question at specific depths. Regularisation techniques have been used to solve the governing Fredholm integral equation to determine the depth-dependent diffractograms. The method has been validated by the use of simulated data having known model profiles, and has also been applied to experimental data from polycrystalline thin film samples.

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Unraveling the Structure of Decagonal Approximants by “Brute Force” Deconvolution of the Experimental Autocorrelation Function

MRS Proceedings ◽

10.1557/proc-643-k5.3 ◽

2000 ◽

Vol 643 ◽

Author(s):

Michael A. Estermann ◽

Katja Lemster ◽

Walter Steurer

Keyword(s):

Autocorrelation Function ◽

Diffraction Data ◽

Brute Force ◽

X Ray Diffraction ◽

Large Unit ◽

X Ray ◽

Structure Building ◽

Lack Of Information ◽

Structure Solution ◽

Unit Cells

AbstractMethods for the ab initio structure analysis of periodic approximant phases from single- crystal X-ray diffraction data are presented. These methods are particularly suited to complex approximant structures with large unit cells and strong pseudosymmetry (where routine X-ray structure solution tools fail) and are based on the “brute-force” deconvolution of the experimentally measured autocorrelation function. This function is obtained directly by a simple Fourier transform of the measured X-ray diffraction intensities. Sub-optimal diffraction data from twinned, nanodomain and polycrystalline specimens can be processed despite the inevitable lack of information due to reflection overlap and limited resolution. The deconvolution process allows complex approximant structures to be unraveled without prior knowledge about the structure-building motifs. Examples are presented for the systems Al-Co-Ni and Al-Co-(Ta).

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