Empirical Texture Corrections for Asymmetric Diffraction and Inclined Textures

Empirical texture corrections have been generalized to include asymmetric diffraction geometries and inclined textures.

On the Principle of a Geometric Mean of Even-Rank Symmetric Tensors for Textured Polycrystals

The mathematics of the geometric mean are explained in detail including practicable working formulas and numerical examples.

Study of Imperfections and Structure in Nonlinear-Optical Crystals of β-BaB₂O₄

Ordinary helical inclusion-induced dislocations and dislocation loops and their mobility, electrodomain, growth boundary etc. in crystals of β-BaB₂O₄ have been studied by X-ray topography. The inclusion formation is discussed in terms of the microphase transition from the β to the α phase or vice versa.

Effects of Surface Relaxation on Powder Diffraction Patterns of Very Fine Particles

A simple model of surface relaxation in nanocrystals generates powder lines whose Gaussian shapes and asymmetric tails mimic details observed in diffraction patterns of colloidal ferrite particles. This suggests that surface relaxation in nanoparticles can be measured with this old technique.

Fourier Filtering of Synchrotron White-Beam Topographs

Fourier filtering is applied to the image analysis of synchrotron white-beam topographs. An optimum filter shape is described that provides accurate filtering without Gibbs diffraction artefacts.

Misorientation-Angle Distribution of Randomly Oriented Symmetric Objects

Distributions of misorientation angle of randomly oriented symmetric objects are calculated. They are reference distributions for analysis of misorientations of crystallites in textured polycrystalline materials.

Study of Growth Defects and Structure in Nonlinear-Optical Crystals of Lithium Boric Oxide

Grown-in dislocations and fringes, inclusions, inclusion-induced dislocations and twinned growth have been studied by X-ray topography, and are discussed in terms of the open structure and structural characteristics in crystals of lithium boric oxide.

The Isoscattering Points in X-ray or Neutron Scattering Curves of One- and Two-Dimensional Systems Measured by the Contrast-Variation Method

The conditions for appearance of the isoscattering points of one-and two-dimensional systems are theoretically derived.

Thermal Expansion of Caesium Halides with the CsCl Structure

Thermal expansion of caesium halides has been approximated by contributions from a quasiharmonic perfect crystal and its thermal defects. Correction to J. Appl. Cryst. (1995). 28, 306-313.

A Novel Beam-Conditioning Monochromator for High-Resolution X-ray Diffraction

A novel du Mond configuration for high-resolution X-ray diffraction is described. It uses two channels cut in blocks of silicon to provide high-intensity and high-resolution settings, switching being by linear translation.

Angle Calculations for a `2+2' Surface X-ray Diffractometer

Angle calculations and corrections for a new type of diffractometer, which has two degrees of freedom for the sample and two degrees of freedom for the detector, are presented.

X-ray Powder Diffraction Structure of Triclinic C₆₀Br₂₄(Br₂)₂

This paper describes a triclinic phase of the fullerene derivative of C₆₀Br₂₄ and discusses the transition between it and the high-temperature rhombohedral phase. The structure was solved by Rietveld refinement of a data set taken with synchrotron radiation.

Discrete Thickness Fluctuations in Fe₃O₄/CoO Multilayers

Interfacial disorder in (111)-Fe₃O₄/CoO multilayers is investigated by X-ray diffraction. Kinematical structure-factor calculations indicate that discrete interfacial disorder explains the observed selective multilayer splitting.

Dictionary of Protein Stereochemistry

A computer-readable dictionary for protein structure refinement is presented that is based on the set of parameters derived from small-molecule structures. Preliminary results obtained from protein structures refined at atomic resolution are compared with this.

Development of a Low-Temperature X-ray Diffractometer with a Weissenberg Camera utilizing an Image Plate

A new type of X-ray apparatus with an image plate as an area detector has been developed in order to study phase transitions at low temperatures. Oscillation and Weissenberg photographs down to 12 K have been taken.

DEMON/ANGEL: a suite of programs to carry out density modification

The DEMON/ANGEL software suite has been developed for density modification by noncrystallographic symmetry averaging, solvent flattening and histogram mapping

LLM: a convolution-based algorithm to simulate the thermal diffuse X-ray scattering from protein crystals using the liquid-like-motion model

A computer program has been developed to simulate the thermal diffuse scattering from protein crystals. The parameters revealed by this program indicate the coupling of the disorder of the atoms in the protein molecule.

The `lattice-parameter comparator': a symmetrical axially reversible mounting for two goniometer heads

A device designed primarily for use with monochromatized synchrotron radiation for making comparisons of lattice parameters in different parts of the same crystal, or between two separate crystals, is described.

A heating device for four-circle diffractometers

A heating device for diffractometers is described that uses a hot stream of nitrogen gas to heat the crystal.

Picosecond time-resolved X-ray diffraction during laser-pulse heating of an Au(111) crystal

Picosecond Cu Kα X-ray pulses have been used to probe the lattice of a single gold crystal heated by 10 ps optical pulses. Time resolution of 50 ps has been achieved.

Increasing the size of microcrystals by fine sampling of pH limits

A simple procedure is described that may be useful for increasing the suitability of small crystals of macromolecules for X-ray analysis. It is based on the careful pH titration of mother liquors at the pH limits for the appearance of crystals.

DBWS-9411 – an upgrade of the DBWS*.* programs for Rietveld refinement with PC and mainframe computers

The latest upgrade and the sequencing of the widely used DBWS*.* series of programs are described.

Crystallographers

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