High-resolution three-dimensional reciprocal-space mapping of InAs nanowires

Grazing-incidence X-ray diffraction is combined with a two-dimensional pixel detector to obtain three-dimensional reciprocal-space maps of InAs nanowires grown by molecular beam epitaxy.

PDB_REDO: automated re-refinement of X-ray structure models in the PDB

The majority of previously deposited X-ray structures can be improved by applying current refinement methods.

Implementation and use of robust refinement in powder diffraction in the presence of impurities

A modification to the usual least-squares analysis is implemented, to refine structural parameters from powder diffraction data containing an unmodeled impurity. The method is characterized using known materials, and two new structures are refined using the method.

High-energy X-ray diffuse scattering

The use of high-energy X-rays as a tool to map the diffuse scattering in reciprocal space is discussed. Particular emphasis is put on the influence of multiple scattering effects on the measured intensity distributions.

A rigorous comparison of X-ray diffraction thickness measurement techniques using silicon-on-insulator thin films

For ideal specimens, thin-film thickness values obtained from high-resolution X-ray diffraction techniques have accuracies of about 1 nm and precisions one or two orders of magnitude smaller. The use of multiple X-ray techniques is required to ensure reliable thickness determination.

Morphology and etch figures of a Yb:YAl₃(BO₃)₄ crystal

The etch figures of three forms ({110}, {20} and {101}) of the self-frequency-doubling crystal Yb:YAl₃(BO₃)₄ were observed and the point group 32 was displayed. Etch figures of faces or sections with the same indices in Yb:YAl₃(BO₃)₄ and quartz are very similar, although their crystal structures are very different.

Elastic constants of fibre-textured thin films determined by X-ray diffraction

Supposing the Hill grain-interaction model, it is demonstrated that X-ray elastic constants can be used to determine mechanical elastic constants of cubic fibre-textured thin films. The new approach is demonstrated by the experimental characterization of out-of-plane moduli of fibre-textured Cu and CrN thin films.

Preferred orientation of ettringite in concrete fractures

Hard synchrotron X-ray microdiffraction is used to quantify the orientation distribution of ettringite crystals [Ca₆Al₂(OH)₁₂(SO₄)₃·26H₂O], which cause cracking and loss of strength in concrete structures.

Enantiomorph identification and stacking faults in κ-(BEDT-TTF)₂Cu(NCS)₂ by convergent-beam electron diffraction

The enantiomorphs of an ambient-pressure superconductor κ-(BEDT-TTF)₂Cu(NCS)₂ [BEDT-TTF is bis­(ethyl­ene­dithio)­tetra­thia­fulvalene] have been successfully identified using the method of convergent-beam electron diffraction. This indicates that a micrometre-sized small crystallite is enough to identify its enantiomorphs even in an organic crystal. Stacking faults in κ-(BEDT-TTF)₂Cu(NCS)₂ have also been found, the existence of which has not been noted from conventional X-ray diffraction methods.

Coordination number in ideal spherical nanocrystals

The decrease of average atomic coordination number with size in nanocrystals is evaluated using calculations based on ideal spherical crystals.

Size distribution and surface characteristics of silicon nanoparticles

The size distribution and morphology of silicon nanoparticles have been studied using small-angle X-ray scattering and transmission electron microscopy. Milled particles exhibit surface fractal characteristics and a high size dispersion, whereas particles produced by silane pyrolysis are smooth with a monodisperse distribution.

A prototype environmental gas cell for in situ small-molecule X-ray diffraction

The development of a prototype environmental gas cell, capable of allowing a single crystal to be exposed to different gas mixtures and/or a vacuum whilst in situ on the single-crystal diffractometer, is reported along with an initial case study.

High-pressure small-angle neutron scattering studies of glucose isomerase conformation in solution

Small-angle neutron scattering (SANS) studies of glucose/xylose isomerase indicate that the structure of this protein in solution is very stable and very similar to that in the crystal, in a broad pressure range up to 150 MPa. This enzyme can be used as a secondary standard for SANS measurements.

Ultra-small-angle X-ray scattering at the Advanced Photon Source

The design and operation of a versatile ultra-small-angle X-ray scattering instrument at the Advanced Photon Source at Argonne National Laboratory are presented.

On the tetragonality of the room-temperature ferroelectric phase of barium titanate, BaTiO₃

The recent interpretation in the literature of the diffraction pattern of top-seeded BaTiO₃ as a hybrid structure of monoclinic and tetragonal phases is dismissed in favour of a twinning model, which has been derived from single-crystal CCD diffraction data and confirmed by simulations. BaTiO₃ at room temperature is proved conclusively to be a single phase of tetragonal symmetry.

High-performance compact-multi-crystal analyzer for X-ray diffractometer scans

A new high-performance diffracted-beam analyzer consisting of multiple pieces of a perfect crystal in the form of a simple and compact device is proposed. The X-ray intensity diffracted from the analyzer can be increased by, for example, one order of magnitude compared with that obtained with an ordinary single-crystal analyzer.

Lattice parameter determination using a curved position-sensitive detector in reflection geometry and application to Sm_x/2Nd_x/2Ce_1–xO_2–δ ceramics

An approach to correct for the effect of sample displacement from the Bragg plane on peak position is described for reflection-mode Debye–Scherrer geometry and applied to determine the relationship between composition and lattice parameter in Sm_x/2Nd_x/2Ce_1−xO_2−δ ceramics.

Anisotropic phonon density of states: the application of Rietveld and Mössbauer texture analysis in aligned powders

Measuring the anisotropic properties of materials, such as phonon densities of states, is possible on an anisotropic polycrystal with a well known orientation distribution function (ODF). With this purpose, the ODF is characterized by Rietveld and Mössbauer texture analysis.

Energy-dispersive diffraction studies of inert anodes

Energy-dispersive diffraction data from the Synchrotron Radiation Source at Daresbury Laboratories have been analysed using crystal-structure-based Rietveld refinement. A standardless quantification method has been developed to analyse directly in energy space rather than in d space. Standard mixtures have been quantified to verify the method which has then been applied to a tomographic study of an electrochemical cell.

Determination of the degree of preferred orientation within the March–Dollase approach

An analytic expression has been derived which connects the degree of preferred orientation in a polycrystalline material to the March parameter. The latter defines the spread of angular distribution of crystallite inclinations in the March–Dollase approach.

Determination of surface crystallography of faceted nanoparticles using transmission electron microscopy imaging and diffraction modes

A general method to determine the surface crystallography and therefore the shape of faceted nanoparticles by transmission electron microscopy is proposed.

Facilitating protein crystal cryoprotection in thick-walled plastic capillaries by high-pressure cryocooling

The minimal concentrations of three common cryoprotectants were determined for high-pressure cryocooling of water in thick-walled plastic capillaries. The substantial reduction in the minimal concentrations by high-pressure cryocooling can be of significant use in high-throughput X-ray protein structure determination.

A sample cell for diffraction studies with control of temperature, relative humidity and applied electric field

This paper describes the design of various sample cells providing a controlled environment for small single crystals or epitaxial thin films during diffraction experiments.

The pseudo-single-crystal method: a third approach to crystal structure determination

A novel method that enables single-crystal diffraction data to be obtained from a powder sample is presented.

ReX: a computer program for structural analysis using powder diffraction data

The ReX software provides a user-friendly environment for structural analysis using powder diffraction data.

HATODAS II – heavy-atom database system with potentiality scoring

HATODAS II, which provides comprehensive suggestions for the heavy-atom derivatization of protein crystals, is described.

Crystallization columns in a laboratory furnace

A model of an air cooler in a laboratory furnace is presented. The setup allows for simultaneous regulation of different crystallization fronts and rates in crucible columns, enabling rapid acquisition of crystals in an undergraduate laboratory.

Re-evaluation of formulae for X-ray stress analysis in polycrystalline specimens with fibre texture. Erratum

Errors in the paper by Yokoyama & Harada [J. Appl. Cryst. (2009), 42, 185–191] are corrected.

Dominique Grebille (1957–2009)

Richard J. Weiss (1923–2008)

Forthcoming meetings and short courses