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Since the edge-to-edge matching relationship of close-packed planes on an incoherent interphase boundary was found, the one-dimensional ledge migration mechanism has been put forward. However, owing to the lack of direct experimental evidence, the existence of the one-dimensional ledge is still questioned and it is thus usually treated as just an assumption. In this study, focusing on the existence of one-dimensional ledges and the migration mechanism of incoherent interphase boundaries, an atomic scale investigation on the migration of incoherent interphase boundaries in a body- to face-centered cubic transformation has been carried out using the phase-field crystal model. Simulation results demonstrated the presence of one-dimensional ledges on incoherent interphase boundaries, but only on those boundaries with high atomic densities. The simulation results further showed that the interphase boundaries with one-dimensional ledges migrate as a result of the nucleation and extension of the one-dimensional ledge, similar to the mechanism for two-dimensional ledges; meanwhile the interphase boundaries without one-dimensional ledges migrate according to a continuous mechanism by random atomic jumping. Because it is difficult for one-dimensional ledges to nucleate under low driving forces, interphase boundary migration based on the one-dimensional ledge mechanism is slower than that based on the continuous mechanism. This study reveals the structures and mechanisms of complex transitions of incoherent interphase boundaries and can aid a deeper understanding of solid phase transformations.

The results are presented of a feasibility study for the application of absorption corrections to macromolecular crystallographic X-ray diffraction data using a three-dimensional crystal model generated photographically. The model allows path lengths through the crystal, the solvent and the crystal mount system to be determined. The approach has been tested on the macromolecular crystallography beamline ID23-1 at the ESRF in Grenoble using a model insulin system with the standard mini diffractometer facilities, which incorporate high-quality camera systems for sample alignment. Data from the insulin crystal at low incident beam energy (6.0 keV or 2.1 Å) were recorded and processed using this approach. The resulting data are compared against those treated using an empirical method and show significant improvement. The methods described here are of general interest, particularly for long-wavelength X-ray work, and may also be applied to account for absorption effects in neutron crystallography.

A transmission electron microscopy study reveals that the so-called twelvefold quasicrystal Ta 62 Te 38 is a crystal subjected to structure modulation. It is composed of two incommensurate layers rotated by 30° to each other about their normal. High-resolution electron microscope images show the formation of commensurate domains and their discommensuration. The observed electron diffraction patterns may be explained by a kinematical calculation for the commensurate cell, designated as a 7 × 7 cell. The modulation is considered to be due to the rearrangement of atomic vacancies in response to the occurrence of charge-density waves.

A method of X-ray line-broadening analysis is presented whereby the coherence length and microstrain contributions can be calculated using a Monte Carlo interference-function-fitting algorithm. The method is based on the `column-like' crystal model and can be applied to both single and multiple-order reflections. Examples on simulated diffraction peaks, deformed face-centred-cubic palladium powder and heavily textured deformed body-centred-cubic low-carbon-steel sheets are presented and comparisons are made with currently applied methods.

The models used up to now for the calculation of powder patterns of layer minerals containing defects have adopted a Markovian hypothesis for the law of defect occurrence. One consequence of this hypothesis is that in a powder obeying this law the particles differ in their contents (chemical composition and/or abundance of stacking defects). Another model can be considered in which the particles have identical contents of each type of layers or stacking defects. This is denoted here by the `identical contents crystal model' (ICC model). In this article are described: (i) the calculation of diffracted intensities for the ICC model and its comparison with that of the Markovian one, and (ii) the application of this calculation to a two-component mixed-layer system. It is shown which kind of modification of intensities or peak positions occur with the ICC model for thin crystals.