Cover illustration: Electrostatic equilibrium of simultaneous Coulomb attraction and core repulsion for an ensemble ; the conjoint centroids, shown in yellow, characterize force-free positions of the fragment inside the unit cell. For comparison, the pure Coulomb equilibrium is shown in the background. See Mädler, Behrends & Knorr [Acta Cryst. (2001). A57, 20-23].
The orbital ordering effect of the Mn2+ ion on the structure factors of an LaMnO3 crystal have been calculated. Lower-order structure-factor measurement methods such as Bragg X-ray and the QCBED method are discusssed and compared.
Thanks to a new interpretation of the direct-methods modulus sum function, its relation to other existing phase-refinement functions can be easily visualized. The behaviour of the modulus sum function has been optimized by analysing the effect of the two most important control parameters on a selection of test structures.
A detailed analysis of multiple diffraction data collected by the stereoscopic multibeam imaging technique from a tetragonal lysozyme crystal is reported. The proposed procedures provide a practical way of reconstructing diffraction profiles for experimental phase determination for macromolecular crystals.
Analysis of X-ray integrated intensities measured as a function of crystal thickness revealed that the two correlation lengths in the theory are absolutely required to interpret the variations of the intensities. It is shown that X-ray diffraction is more sensitive to the two correlation lengths than γ-ray diffraction.
An analysis of the normal modes of vibration of a cubic perovskite that have condensed out to produce phases with tilted octahedra is presented. A Landau expansion of the excess free energy is presented involving the seven distinct modes found in the possible structures.
A simple tiling of Euclidean space by infinite tiles with all hexagonal faces is described and related to a dense cylinder packing with symmetry Iad. Some related structures with the same symmetry are also described.