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

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.

D-5 The Direct Determination of X-ray Diffraction Data from Specific Depths

2004 ◽  
Vol 19 (2) ◽  
pp. 195-195
Author(s):  
A. Broadhurst ◽  
K. D. Rogers ◽  
D. W. Lane ◽  
T. W. Lowe
Keyword(s):  
Diffraction Data ◽  
Direct Determination ◽  
X Ray Diffraction ◽  
X Ray

Determination of depth profiles from X-ray diffraction data

1993 ◽  
Vol 8 (2) ◽  
pp. 122-126 ◽  
Author(s):  
Paul Predecki
Keyword(s):  
Diffraction Data ◽  
Direct Method ◽  
Sample Surface ◽  
Data Sets ◽  
X Ray Diffraction ◽  
Data Set ◽  
X Ray ◽  
Depth Profiles ◽  
A Direct Method

A direct method is described for determining depth profiles (z-profiles) of diffraction data from experimentally determined τ-profiles, where z is the depth beneath the sample surface and τ is the 1/e penetration depth of the X-ray beam. With certain assumptions, the relation between these two profile functions can be expressed in the form of a Laplace transform. The criteria for fitting experimental τ-data to functions which can be utilized by the method are described. The method was applied to two τ-data sets taken from the literature: (1) of residual strain in an A1 thin film and (2) of residual stress in a surface ground A12O3/5vol% TiC composite. For each data set, it was found that the z-profiles obtained were of two types: oscillatory and nonoscillatory. The nonoscillatory profiles appeared to be qualitatively consistent for a given data set. The oscillatory profiles were considered to be not physically realistic. For the data sets considered, the nonoscillatory z-profiles were found to lie consistently above the corresponding τ-profiles, and to approach the τ-profiles at large z, as expected from the relation between the two.

scholarly journals Crystallization and X-ray diffraction data analysis of human deoxyhaemoglobin A0 fully stripped of any anions

1999 ◽  
Vol 55 (11) ◽  
pp. 1914-1916 ◽  
Author(s):  
F. A. V. Seixas ◽  
W. F. de Azevedo ◽  
M. F. Colombo
Keyword(s):  
Diffraction Data ◽  
Oxygen Affinity ◽  
X Ray Diffraction ◽  
Structural Explanation ◽  
Human Haemoglobin ◽  
X Ray ◽  
High Resolution Structure ◽  
Allosteric Properties

In this work, initial crystallographic studies of human haemoglobin (Hb) crystallized in isoionic and oxygen-free PEG solution are presented. Under these conditions, functional measurements of the O2-linked binding of water molecules and release of protons have evidenced that Hb assumes an unforeseen new allosteric conformation. The determination of the high-resolution structure of the crystal of human deoxy-Hb fully stripped of anions may provide a structural explanation for the role of anions in the allosteric properties of Hb and, particularly, for the influence of chloride on the Bohr effect, the mechanism by which Hb oxygen affinity is regulated by pH. X-ray diffraction data were collected to 1.87 Å resolution using a synchrotron-radiation source. Crystals belong to the space group P21212 and preliminary analysis revealed the presence of one tetramer in the asymmetric unit. The structure is currently being refined using maximum-likelihood protocols.

Direct Determination of Stress Levels in Sputtered Films by means of X-Ray Diffraction Topographic Method

1987 ◽  
Vol 26 (Part 1, No. 1) ◽  
pp. 157-161 ◽  
Author(s):  
Osamu Nittono ◽  
Yoshihiro Sadamoto ◽  
Sheng Kai Gong
Keyword(s):  
Direct Determination ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sputtered Films ◽  
Stress Levels

scholarly journals Rubidium tetrafluoridobromate(III): redetermination of the crystal structure from single-crystal X-ray diffraction data

IUCrData ◽  
2019 ◽  
Vol 4 (11) ◽  
Author(s):  
Artem V. Malin ◽  
Sergei I. Ivlev ◽  
Roman V. Ostvald ◽  
Florian Kraus
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Single Crystals ◽  
Diffraction Data ◽  
Structure Type ◽  
X Ray Diffraction ◽  
X Ray ◽  
Square Planar ◽  
Atomic Coordinates

Single crystals of rubidium tetrafluoridobromate(III), RbBrF4, were grown by melting and recrystallizing RbBrF4 from its melt. This is the first determination of the crystal structure of RbBrF4 using single-crystal X-ray diffraction data. We confirmed that the structure contains square-planar [BrF4]− anions and rubidium cations that are coordinated by F atoms in a square-antiprismatic manner. The compound crystallizes in the KBrF4 structure type. Atomic coordinates and bond lengths and angles were determined with higher precision than in a previous report based on powder X-ray diffraction data [Ivlev et al. (2015). Z. Anorg. Allg. Chem. 641, 2593–2598].

Ab initio structure determination of anhydrous sodium alendronate from laboratory powder X-ray diffraction data

2009 ◽  
Vol 98 (6) ◽  
pp. 2113-2121 ◽  
Author(s):  
Minakshi Asnani ◽  
K. Vyas ◽  
Apurba Bhattacharya ◽  
Surya Devarakonda ◽  
Santu Chakraborty ◽  
...  
Keyword(s):  
Ab Initio ◽  
Diffraction Data ◽  
Structure Determination ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ab Initio Structure
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