Qu­antitative texture analysis of small domains with synchrotron radiation X-rays

A method of quantitative texture analysis of small domains of material is presented and illustrated with examples from metal wires, polymer fibres and bone material.

Correction of zero shift in powder diffraction patterns using the reflection-pair method

An equation is derived to calculate the 2θ zero shift in powder diffraction patterns based on the reflection-pair method. The equation can be used before indexing to diagnose and correct the 2θ zero shift.

Determination of polarity in noncentrosymmetric layer/substrate systems

Energy-dispersive anomalous X-ray scattering has been used to determine the polarity of an epitaxially grown (Ga,In)P layer on a (001) GaAs substrate as an example to show the applicability of this method as a routine procedure for non-centrosymmetric thin-film systems.

Localized destructive interference in X-ray specular reflectivity

The superlattice features giving localized destructive interference in X-ray specular reflectivity are analysed with a simple kinematical model. This effect can be used to obtain energy filters at fixed incidence angle.

Combined method for ab initio structure solution from powder diffraction data

A new direct-space method for ab initio solution of crystal structures from powder diffraction data by combined global optimization of pattern difference and potential energy is described.

Investigation of Bragg surface diffraction in semiconductors and epitaxic structures by reciprocal-space analysis

Attenuation of the X-ray wavefield in GaAs and Si under Bragg surface diffraction and the existence of effective satellite peaks in multiple quantum wells are described.

Gamma-ray sensitivity and shielding of a neutron imaging plate

When a neutron imaging plate is used as detector, the gamma-ray background cannot be ignored. The effects of gamma rays on a neutron imaging plate and how to shield the imaging plate are reported.

The influence of cylindrical geometry on X-ray stress tensor analysis. II. Applications

The general scheme of X-ray stress analysis on cylindrical surfaces is simplified for many practical cases. This can be used to validate experimental conditions and apply corrections to take into account the effect of geometry.

Small-angle scattering intensity behaviours of cylindrical, spherical and planar lamellae

The small-angle scattering intensities of cylindrical and spherical lamellar grains are analytically determined.

The application of evolution strategies to disordered structures

Evolution strategies have been applied to explain the electron densities of orientationally and conformationally disordered structures and to refine disordered fragments. In connection with concepts from qualitative physics, the strategies were used to compute reorientation pathways and to model high-pressure behaviour in a virtual experiment.

Estimation of radial distribution functions in electron diffraction experiments: physical, mathematical and numerical aspects

Calculations of the radial distribution function in a diffraction experiment by Fourier transform and by a maximum-entropy algorithm give similar results on data with little error margin. In this case the Fourier transform is numerically more robust than the maximum-entropy method.

Small-angle scattering from collections of interacting hard ellipsoids of revolution studied by Monte Carlo simulations and other methods of statistical thermodynamics

Monte Carlo simulations are used to calculate the small-angle scattering, the nonideal part of the chemical potential and the compressibility factor for ellipsoids of revolution of varying concentrations and eccentricities. Comparisons are also made with results obtained from the literature.

Morphological and synchrotron X-ray microdiffraction studies of large columnar CVD diamond crystallites

Combined application of optical microscopy, goniometry, synchrotron X-ray microradiography, diffraction and topography identifies and spatially localizes imperfectly crystalline twinned regions in columnar growths in which the core volume is substantially unstrained and free of lattice defects.

Analysis of weighting schemes

Refinements of known structures using different weighting schemes produce differing results.

Angle calculations for a six-circle κ diffractometer

A new procedure for angle calculations based on the intersections of conic surfaces is presented. It is applied to a six-circle κ diffractometer.

The coherent electron microdiffraction of a single translation domain boundary in β-Ni₃Nb phase

The microdiffraction from a single translation domain boundary (TDB) in β-Ni₃Nb was recorded using a Hitachi HF-2000 FEG TEM microscope. The diffraction splitting effect of a TDB is well explained by the kinematics and dynamics calculations.

Derivation of infinite-slit-smeared small-angle scattering from porous surface and porous mass fractals

Simple derivations for infinite-slit-height-smeared SAXS from porous surface and mass fractals are presented, including an approximation for aggregated mass fractals.

Solving crystal structures from powder data. V. Located molecular fragment and powder-pattern decomposition

Prior information on a structural fragment is used to improve the efficiency of the powder-pattern decomposition.

Etude structurale par diffraction des RX et spectroscopie IR des hydrates 10 et 8.4 Å de kaolinite

An X-ray diffraction study of two hydrated kaolinites, characterized by 10 and 8.4 Å basal distances, is reported. The study is based on a comparison between the experimental and calculated profiles.

Subpicosecond X-ray diffraction study of laser-induced disorder dynamics above the damage threshold of organic solids

Ultrafast atomic disordering in Langmuir–Blodgett (LB) films and TlAP crystals has been investigated by femtosecond time-resolved X-ray diffraction experiments using intense laser pulses.

Effect of sample transparency in powder diffractometry with Bragg–Brentano geometry as a convolution

Mathematical formulae for the effect of sample transparency in powder diffractometry with Bragg–Brentano geometry are examined. The overall profile function given by triple convolution of the pseudo-Voigt function with the horizontal divergence, sample transparency and vertical divergence aberration functions reproduces the experimental peak profiles well.

The contrast factors of dislocations in cubic crystals: the dislocation model of strain anisotropy in practice

In the dislocation model of strain anisotropy, the contrast factors of dislocations play the most important role. In texture-free cubic polycrystals or powders, the contrast factors are a function of two parameters only, which are compiled for a wide range of elastic constants.

Cryocrystallography with oil – an old idea revived

A method is described that permits the cooling of protein crystals with paraffin oil instead of conventional cryoprotective agents.

An improved method for protein crystal density measurements

Simple methods for the preparation of organic solvent density gradients and the transfer of protein crystals into these gradients are described.

X-ray diffraction study of anisotropic thermal expansion in ZrMo₂O₈

X-ray diffraction measurements of the trigonal phase of ZrMo₂O₈ from 80 to 925 K reveal highly anisotropic thermal expansion behaviour.

XAct: a program for construction, automated setup and bookkeeping of crystallization experiments

A program for Microsoft Windows™ 95/98 is described that allows the use of a Gilson 222 autosampler (Gilson Inc., Wisconsin, USA) to set up many crystallization trials automatically.

MIMS: a program for measuring four-dimensional Fourier maps of incommensurate modulated structures

The program MIMS (measuring incommensurate modulated structures) has been written for the determination of structural parameters of incommensurate one-dimensionally modulated structures by automatic search on four-dimensional Fourier maps.

Facilitating preparation of gaskets for routine high-pressure diffraction studies

A method of mounting sample crystals in high-pressure diamond-anvil cells, aimed at facilitating the procedure of preparation of gaskets, and a simple spark eroder for laboratory use are described.

Position-sensitive ionization chambers in the alignment of X-ray tubes and diffractometers

Compact split-plate ionization chambers are described for the alignment in two orthogonal planes of microfocus X-ray tubes to X-ray diffractometers or goniometers.

MSG (Molecular Scene Generator): a Web-based application for the visualization of macromolecular structures

MSG provides a simple Web-based input form as an interface to the Molscript program for rendering the structures of biological macromolecules in Protein Data Bank (PDB) format. Output consists of a VRML rendition of the molecule viewable in a web browser.

JSV1.07 – a Java structure viewer

A software package for visualizing various crystallographic aspects is presented.

JMap3D – VRML isosurface generator

A Java program for rendering electron-density data as VRML isosurfaces is presented.

DIAMOND – Visual Crystal Structure Information System

DIAMOND, reviewed by W. T. Pennington.

Materials crystal chemistry

Oxford Cryosystems North America