Direct analysis of small-angle smeared intensity tails. I. General results

The asymptotic leading terms of small-angle scattering smeared intensities are discussed and numerically analysed. The smeared oscillatory contributions in practice coincide with those smeared by an ideal slit.

Direct analysis of small-angle smeared intensity tails. II. Applications

The shape and particle sizes of two triblock copolymers are obtained from the analysis of the tails of the smeared small-angle X-ray intensities. In one of the samples, particles are found to be organized as in a dense hard-sphere fluid.

A maximum entropy method for determining column-length distributions from size-broadened X-ray diffraction profiles

This paper discusses the application of a twofold maximum entropy method for determining specimen profiles and crystallite size distributions, and their corresponding uncertainties, from size-broadened X-ray diffraction profiles. Simulated size-broadened profiles are used to demonstrate the application of the method.

Angle calculations for a `4S+2D' six-circle diffractometer

Angle calculations are derived for the operation of a `4S+2D' six-circle X-ray or neutron diffractometer. Four sample-orienting and two detector-orienting degrees of freedom are used to control the scattering vector and a reference vector in the laboratory frame of reference.

Measurement of single-crystal elastic constants by neutron diffraction from polycrystals

Expressions are developed relating the diffraction elastic constants for a polycrystalline material to the single-crystal elastic constants for crystal systems with orthorhombic and higher symmetry. It is shown that these expressions may be used to extract single-crystal elastic constants from measurements on polycrystals or, alternatively, may be used to provide insight into the stress–strain state in polycrystalline samples by a comparison of measured and calculated diffraction elastic constants.

Flat-specimen effect as a convolution in powder diffractometry with Bragg–Brentano geometry

Mathematical formulae of the flat-specimen effect in powder diffractometry with Bragg–Brentano geometry are examined.

Optimization of resolution–intensity balance in angular-dispersive powder diffractometry at a synchrotron radiation source

A unique resolution function of angular-dispersive powder diffractometers, properly parametrized to be valid for any multicrystal variant of the instrument, has been derived. A computer simulation method offers reliable information, useful for designing diffractometers and conducting experiments.

On the number of independent reflections in a powder diffraction pattern

The number of independent reflections in a powder diffraction pattern is derived from the eigenvalues of the integrated intensities covariance matrix obtained from a Pawley analysis.

Difference structure-factor normalization for heavy-atom or anomalous-scattering substructure determinations

Procedures are described for preparing single-derivative isomorphous replacement and single-wavelength anomalous scattering difference-magnitude data for probabilistic direct-methods phasing.

Fourier modelling of the anisotropic line broadening of X-ray diffraction profiles due to line and plane lattice defects

A new model of line-profile broadening due to the effect of linear and planar lattice defects has been incorporated into the conventional Rietveld algorithm for the structural refinement and whole-pattern fitting of powder data. Theory is presented along with examples of applications to face-centred cubic structures.

Deconvolution of the two-dimensional point-spread function of area detectors using the maximum-entropy algorithm

The maximum entropy algorithm is used to deconvolute the point-spread function of two-dimensional area detectors. This results in significant image enhancement.

Simulations of femtosecond X-ray diffraction from unperturbed and rapidly heated single crystals

Simulations are presented of the dynamical diffraction of femtosecond pulses of X-rays from crystals whose structures are modified on similar time scales. Such simulations are of relevance to experiments in which short pulses of X-rays from synchrotron or laser sources are diffracted from rapidly laser-heated crystals.

Qu­antitative phase analysis of α- and β-silicon nitrides. I. Estimation of errors

Errors in the quantitative phase analysis (QPA) of α- and β-silicon nitrides (Si₃N₄) using the mean normalized intensity method and the Rietveld method were estimated in theory and experiments.

Qu­antitative phase analysis of α- and β-silicon nitrides. II. Round robins

Two round robins of the quantitative phase analysis of silicon nitrides using the mean normalized intensity method and the Rietveld method were conducted as one of the projects for establishing standard methods of characterizing advanced ceramic materials.

A Gaussian–Hermite polynomials function for X-ray diffraction profile fitting

This work proposes a new peak-shape function for modelling X-ray powder diffraction profiles, based on the use of the Gaussian function and a Hermite polynomials series expansion.

On the problem of overlapping ω scans measured on thin films deposited on monocrystal substrates

An experimental study on the nature of extremely narrow overlapped maxima on X-ray diffraction ω scans is presented.

Second-order neutron optics of three-axis spectrometers. I. Quasielastic scattering

Second-order aberrations in bent-crystal three-axis spectrometers have been derived and verified experimentally. Substantial improvement of resolution was achieved through control of second-order effects.

High-resolution transmission electron microscopy study of the φ′- and δ-AlON spinel phases of the pseudo-binary section AlN–Al₂O₃

High-resolution electron-microscopy observations support the previous structural model proposed for the φ′- and δ-AlON spinel phases which allows for the double modulation of composition and displacement of the anions and cations.

Structure of sodium para-hydroxybenzoate, NaO₂C–C₆H₄OH by powder diffraction: application of a phenomenological model of anisotropic peak width

The structure of sodium para-hydroxybenzoate has been solved ab initio by high-resolution X-ray powder diffraction; the quality of the powder data permits the detection of the position of the H atom connected to the phenolate. The sample shows extreme anisotropic peak broadening which could be satisfactorily modelled by a recently developed function.

A self-consistent method for X-ray diffraction analysis of multiaxial residual-stress fields in the near-surface region of polycrystalline materials. I. Theoretical concept

The theoretical background of a new formalism in X-ray stress analysis (XSA) is derived. It allows the self-consistent evaluation of steep multiaxial residual-stress gradients in the near-surface region of polycrystalline materials from the strain data, which are measured in the scattering-vector mode of the XSA.

A self-consistent method for X-ray diffraction analysis of multiaxial residual-stress fields in the near-surface region of polycrystalline materials. II. Examples

A newly developed formalism for the analysis of steep residual-stress gradients in the near-surface region of polycrystalline materials is applied to several practical cases. It yields the in-plane stresses, σ₁₁(τ) and σ₂₂(τ), the strain-free lattice spacing, d₀(hkl), and, for well pronounced lattice-spacing depth profiles, even the out-of-plane stress, σ₃₃(τ), in a self-consistent way.

Automatic orientation determination from Kikuchi patterns

Formal aspects of automatic crystal orientation determination from Kikuchi patterns are discussed. Reliability of automatically obtained results and their sensitivity to experimental errors are investigated.

Laboratory X-ray powder diffraction: a comparison of different geometries with special attention to the usage of the Cu Kα doublet

It is shown how measurements using the Kα doublet influence evaluation procedures such as stripping, single-line analysis and Rietveld refinement. Moreover, a detailed description of the line-shape behaviour for different geometrical arrangements of powder diffractometers is given.

X-ray powder diffraction qu­antitative analysis performed in situ at high temperature: application to the determination of NiO in ceramic pigments

This is the first report of the application of in situ high-temperature quantitative phase analysis. The application to NiO in ceramic pigments is described.

Use of an open-flow helium cryostat for macromolecular cryocrystallography

A helium cryostat developed at the University of Toledo has been used to flash-cool and collect data from crystals of lysozyme and myoglobin, including flash-cooled crystals large enough for neutron diffraction purposes. The liquid-He consumption of the device is sufficiently low to allow the acquisition of complete diffraction data from a crystal on a single tank of He, and should expand He-temperature data-collection opportunities.

Pepinsky's Machine: an interactive graphics-based Fourier synthesis program with applications in teaching and research

A computer program has been developed which can be used both as a teaching aid to illustrate the principles and the application of the Fourier series in crystallography, and as a research tool to permit the systematic calculation of permutation syntheses for all centrosymmetric plane groups.

An improved goniometer head for high-temperature single-crystal X-ray diffraction

A reliable and inexpensive goniometer head has been designed and a high-temperature version has been tested at 973 K on a K_0.88Rb_0.12TiOPO₄ crystal.

DATPROC9: a data-processing program based on a new extension of the learnt-profile method

Computer modelling based on the extended learnt profile is used to refine the calculated net intensities. The user may select the learnt-profile model, from three available, in order to obtain a name.hkl file for crystal structure determination or to view the intensity plots of the measured profiles and their models.

A high-temperature furnace for X-ray diffraction with directly machined α-Al₂O₃ ceramic parts

A high-temperature furnace, operating between ambient temperature and 1500 K, is described for the automatic collection of X-ray diffraction data on the Mar345 imaging-plate detector system. The complex ceramic parts were produced from presintered α-Al₂O₃ precompacts.

WinGX suite for small-molecule single-crystal crystallography

WinGX is a suite of Microsoft Windows™ programs for the processing, solution, refinement and publication of single-crystal diffraction data.

PowderX: Windows-95-based program for powder X-ray diffraction data processing

A Windows-95-based program for powder X-ray diffraction data processing, PowderX, is presented.

DISCUS, a program for diffuse scattering and defect structure simulations – update

An update of the program DISCUS for diffuse scattering and defect structure simulations is presented.

XFPA98: a program for automatic structure determination and automatic refinement

XFPA98 is a versatile tool for direct Patterson solution and preliminary refinement of crystal structures.