Determination of the Deformation State of (Zn,Mn)Se/ZnSe Multilayers

A method is presented that links the measured peak separations in X-ray rocking curves to the strain tensor of the epilayer. Different critical thicknesses for the relaxation in the [110] and [110] directions are determined for (Zn,Mn)Se on ZnSe buffer on GeAs substrate.

An Easy Method for the Determination of Debye Temperature from Thermal Expansion Analyses

The phonon contributions to the thermal expansion of solid crystals are studied. The Debye temperature and the values of the lattice parameters exptrapolated to 0 K are determined so that extra contributions (electronic or magnetic) are displayed.

On the Analysis of Reversible Light-Induced Changes in Molecular Crystals

Methods and algorithms are described for the measurement and analysis of the response of crystals to irradiation by pulsed laser light. They are tested in a 40 K study of the 2.44 ms lifetime excited state of [RhBr₂(pyridine-d₅)]Br.

The Ill-Posedness of the Inverse Problem of Texture Goniometry: the Variation Width of Feasible Orientation Density Functions Revisited

Considering the forward problem of deriving and evaluating pole density functions from given crystallographic orientation density functions, it is shown that the corresponding inverse problem is mathematically ill posed. Very different orientation density functions, differing in both even and odd terms of their harmonic series expansion, result in very similar pole density functions.

On the Retrieval of Particle Size Distributions from Small-Angle Scattering Data: the Influence of Statistical Data Dispersion

The problem of the retrieval of the particle size distribution of scatterers from small-angle scattering experiments with noisy data is addressed.

Diffuse X-ray Scattering and Short-Range Order in Thallium Antimonyl Germanate, TlSbOGeO₄

Diffuse scattering has been recorded for the KTP analogue material TlSbOGeO₄, and a preliminary interpretation made using Monte Carlo simulation. The diffuse scattering originates predominantly from the disorder of the thallium cations between alternative sites Tl and Tl^', and the occupancy of these sites tends to alternate along the b crystal direction.

Extinction and Grain-Size Anisotropy Correction of Texture Data Obtained Using Neutron Diffraction

When neutron diffraction is used, texture measurements are affected by extinction and anisotropy of grain size. A method of correction is proposed and tested.

Diffuse Scattering Investigations with a Graphite Double Monochromator for X-ray Synchrotron Radiation: YBa₂Cu₃O_6.5 and KNbO₃

A graphite double monochromator has been built and tested. With a Weissenberg camera and an image plate, diffuse superstructure reflections and diffuse planes have been recorded.

The (hkl) Dependence of Diffraction-Line Broadening Caused by Strain and Size for all Laue Groups in Rietveld Refinement

Models for the anisotropic broadening of the Bragg peaks caused by microstrain and crystallite size are derived for all Laue groups. The models are suitable for implementation in the Rietveld refinement programs.

In Situ Fixed-Angle X-ray Reflectivity Measurement of Thin-Film Roughness and Thickness during Deposition

An oscillating reflective intensity was measured with the sample and detector at fixed specular angles during the thin-film growth. This oscillating intensity carries the information of thin-film thickness and roughness.

Diffractometer Noise Characteristics: Experimental Determination and Application to Statistical Rocking-Curve Analysis

This paper examines the dependence of experimental noise in an X-ray rocking curve and develops a procedure for the use of this noise characteristic as a weight function for the optimization and analysis of calculated fits of the rocking curve.

A (2+3)-Type Surface Diffractometer: Mergence of the z-Axis and (2+2)-Type Geometries

The addition of an azimuthal detector rotation to a (2+2)-type diffractometer makes it fully equivalent to a z-axis type. The geometric correction factors for this (2+3)-type diffractometer, which are needed to obtain structure factors from measured integrated intensities, are derived.

Minimum-Angle versus Low-Index Axis Rotations for Representing Small- and Large-Angle Grain Boundary Misorientations in Cubic Lattices

Some new properties of the least-angle rotation between two cubic crystals are derived. The extent to which a misorientation may alternatively be described by some low-index axis rotation is also examined.

Nanoscale Hardening Precipitiation in AlMgSi Alloys: A Transmission Electron Microscopy and Small-Angle Neutron Scattering Study

Transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) have been used to study hardening precipitation in a 6056 Al–Mg–Cu–Si alloy at peak ageing. TEM gives the precipitate morphology and structure while the SANS data analysis yields their distribution and mean size.

Neutron Storage in a Longitudinally Vibrating Silicon Crystal

The storage of cold neutrons in a longitudinally vibrating silicon crystal is demonstrated by time-resolved transmission experiments on a high-resolution backscattering spectrometer. The experimental results are compared with Monte Carlo simulations.

Surface-Induced Parasitic Scattering in Bonse–Hart Double-Crystal Diffractometers

Surface-induced scattering from Si(111) crystal has been studied and attributed to the network of cracks produced by cutting. This scattering can be significantly reduced by deep etching of the crystal.

Extended Kinematic Approach to the Simulation of High-Resolution X-ray Diffraction Spectra. Application to Structures with Buried Amorphous Layers

A new approach to the simulation of high-resolution X-ray diffraction spectra is developed using direct summation of scattered waves. The simulation procedure permits the introduction of short-range variations of structural and geometrical parameters of multilayered systems.

Cooling Rates During Flash Cooling

Measurements of cooling rates were made for different cryoprotectants with different sample volumes and cooling agents. Approaches by which the increase in mosaic spread during flash cooling of macromolecular crystals might be minimized are discussed.

On the divergence of rays Bragg diffracted by perfect stationary crystals illuminated with collimated polychromatic radiation

Among the various diffraction geometries possible with the incident illumination specified, symmetric Bragg-case reflection has the valuable special property of invariant direction of reflected rays, independent of wavelength and the extinction distance of the reflection.

BEARTEX: a Windows-based program system for qu­antitative texture analysis

This report introduces a software package for quantitative texture analysis, applicable to all crystal symmetries. The 20 computer programs provide for processing of experimental data, calculation of the orientation distribution and anisotropic properties as well as various graphic representations.

Automated and graphical methods for locating heavy-atom sites for isomorphous replacement and multiwavelength anomalous diffraction phase determination

A new program for automatically determining heavy-atom derivative sites from SIR data and anomalous-scatterer sites from MAD-FA coefficients is described. The program is deployed with a set of interactive graphical tools for checking and editing the heavy-atom sites against difference Patterson and cross-difference Fourier maps.

Program to generate and evaluate three-phase structure-invariant ω estimates from single-wavelength anomalous dispersion data

A direct-methods computer program to evaluate Hauptmann's three-phase triple-invariant estimates for single-wavelength anomalous dispersion data is described.

CIF Applications. VII. CYCLOPS2: extending the validation of CIF data names

CYCLOPS2 is a major revision of the program CYCLOPS, which is used, in conjunction with Crystallographic Information File (CIF) dictionaries, to validate names in an ASCII file.

CIF Applications. VIII. pdb2cif: translating PDB entries into mmCIF format

pdb2cif is a new version of an awk script originally written by P. E. Bourne in 1993 to translate from the 1992 Protein data Bank (PDB) format to the macromolecular Crystallographic Information File (mmCIF) definition. This new version of pdb2cif translates all current PDB formats.

A device for low-temperature crystal reorientation in data collection with the oscillation method

A device that allows reorientation of a crystal at low temperature, without remounting or warming to ambient temperature, is described.

A high-transmission furnace insert for neutron powder diffraction studies at high temperatures under a pressurized reactive atmosphere

A new furnace insert has been devised in which a sample can be studied using neutron scattering techniques in situ under several atmospheres of gas pressure and temperatures up to 1350 K.

On the correction of reflection intensities recorded on imaging plates for incomplete absorption in the phosphor layer.

The use of imaging plates as detectors in X-ray crystallography requires a correction for oblique incidence of the diffracted beam on the plate. The correction becomes important for wavelengths less than about 1 Å.

Moving median filters for area-detector data

Moving median filters have been employed to remove impulse noise from two-dimensional area-detector data. The median filters are compared to generalized moving mean filters.