April 2008 issue
Quantitative analysis of the focusing performance of bent Laue crystals is carried out using numerical solution of the Takagi equations and the Fresnel integral. In addition, a formula for the geometrical aberration of a cylindrically bent crystal is derived.
A modification to the Merrill–Bassett diamond anvil cell is presented. This design incorporates tungsten carbide backing disks and Boehler–Almax-cut diamonds which permit the full opening angle, and maximum pressure attainable to remain comparable with the previous backing seat and anvil design, whilst removing troublesome beryllium.
Small-angle equidistant meridional reflections from intramuscular shad/herring bone were analyzed on the basis of a two-dimensional fitting scheme that takes preferred orientation effects into account.
InAs nanowires that exhibit a significant amount of wurtzite structure have been investigated using phase-sensitive coherent X-ray diffraction with a micro-focused beam at a synchrotron source. Simulations compared with experiments evidence the presence of stacking faults distributed along the wire.
Grazing-incidence X-ray scattering formulas were derived for hexagonally perforated layer systems with ABC and AB stacking sequences in substrate-supported nanoscale thin films. Using these formulas the GIXS data obtained for polystyrene-b-polyisoprene thin films supported on silicon substrates were quantitatively analyzed, providing information about the structural parameters, perforated layer stacking sequence and orientation of the films.
An accurate structure of a mid-sized pharmaceutical compound, prednisolone succinate, has been determined using high-resolution powder data collected at SPring-8 by a newly developed analytical method, which is a combination of a genetic algorithm and the maximum entropy method. The analytical procedures are described in detail.
A nondestructive tomographic imaging technique revealing simultaneously the grain and the absorption microstructure of undeformed polycrystalline materials is described.
An extension to the nondestructive tomographic imaging technique revealing simultaneously the grain and the absorption microstructure of undeformed polycrystalline materials is described. The technique uses simultaneous acquisition of direct and diffracted beams.
An optimal side-chain placement algorithm is adapted to protein crystallographic refinement. Its utility is evaluated for single/multi-conformer refinement and sequence-registry identification.
The feasibility of low-resolution phasing via the single isomorphous replacement method from protein powder data is demonstrated.
Criteria for the evaluation of hardware and software for charge density studies and evaluation of area-detector data are presented.
A high-pressure chamber for conducting laboratory X-ray powder diffraction experiments up to 12.4 MPa has been modified from an existing design. Changes were made to meet current design codes (ASME 31.3), and finite element analysis revealed that thinner Be windows than previously thought could safely be used.
The temporal variation of the surface morphology of Ta2O5 films on Si substrates has been measured using X-ray reflectivity at a fixed angle during radio-frequency magnetron sputtering. During an early stage of growth of polycrystalline Ta2O5, the variation of surface roughness revealed a morphology of island nucleation and island coalescence.
A statistical approach is used to define the long molecular axis and the main molecular plane. From the molecular axes and planes, the orientation of the molecule with respect to the lattice as well as intermolecular orientations can be characterized.
This paper describes the use of in situ high-resolution X-ray diffraction measurements using a conventional laboratory source for the study of the evolution kinetics of very small complexes under annealing.
To ensure concentricity of the θ–2θ rotation stages, but with a very limited 2θ range of rotation, an alignment technique using two dial gauges mounted at right angles to each other (X and Y axes) is described.
The feasibility of a new experimental approach for characterizing the strongly graded, non-equiaxed stress state existing at a machined surface is demonstrated. The results from constant-penetration-depth measurements on the ground surface of an engineering ceramic are compared with those from conventional sin2ψ measurements.
Two distinct methods are compared for the determination of the B-cation chemical short-range order (SRO) parameters from the total scattering pair-distribution function. One of the approaches, which proved to yield the most accurate results, was used to analyze the SRO of Ti and Zr in powder samples of Ca(Zr,Ti)O3.
New measures of sharpness for symmetric powder diffraction peak profiles are proposed. Analytical expressions for typical model profile functions and theoretical size-broadening profiles with statistical size distribution are presented.
This work presents the structural characterization of illite-1M from northern Hungary using state-of-the-art analytical methods available for clays. This is the first attempt to refine the structure model and locate the interlayer water molecule in this clay mineral species.
The contrast mechanism of ultra-small-angle X-ray scattering imaging is explained based on phase propagation and dynamical diffraction theory. A complementary geometrical analysis is also presented.
Pitfalls during non-ambient X-ray diffraction stress analysis of thin films (with nanosized grains) are discussed. Recipes for identifying nanosize-related effects on thermoelastic constants and various sources of residual stresses are provided.
Small-angle scattering data from non-dilute solutions of globular particles are analysed by indirect Fourier transformation without the use of a specific model structure factor.
A model of distorted f.c.c. arrangement for silica-supported gold nanoclusters brings about satisfactory fitting to X-ray diffraction data and is confirmed by EXAFS analysis. Using ordered f.c.c. and noncrystalline (icosahedral and decahedral) components, the X-ray diffraction fitting is also good, but the results are in contrast to EXAFS data.
Making a complete background correction for SANS from solutions of biological macromolecules enables more accurate values for the calculated shapes and sizes of the molecules and leads to valid interpretations of solvation as well as the magnitudes of intermolecular interactions.
The Materials Module of Mercury is introduced, which includes functionality to search the Cambridge Structural Database for packing motifs and to perform structure-similarity calculations. Further new features within Mercury CSD 2.0 include links to IsoStar and ConQuest, visualization of voids and image output to the program POV-Ray.
The Computational Science and Engineering Online (CSE-Online) environment provides various tools and services to crystallographic computing illustrated by an interface to the Crystallography Open Database and Predicted Crystallography Open Database.
ORTEPIII has been adapted to incorporate the CAIRO graphics back-end to improve the output quality and program usability. A simple Python helper for instruction file generation, CIFTEP, is also provided.
The computer program CRYC3D has been developed as a convenient and user-friendly way of calculating basic geometric characteristics of three-dimensional crystallographic objects.
DiXP is a multi-platform open source software that allows the remote control of an X-ray powder diffractometer through the Internet. Its implementation using Python and a client/server architecture make this program of widespread purpose and straightforward generalization.
A simple and flexible system is described for in situ screening of microcrystals of membrane proteins that are grown within a connected-bilayer matrix formed by hydrated lipids. Crystallization wells can be individually excised and mounted for diffraction screening on a synchrotron X-ray source.