issue contents

ISSN: 2053-2733

May 2014 issue

Highlighted illustration

Cover illustration: The calculated distribution of X-ray intensities obtained from rocking a crystal plane about two orthogonal axes. The central peak represents the specular condition. The inset illustrates the capture area for a typical Bragg-Brentano diffractometer. Image from A new theory for X-ray diffraction by Paul F. Fewster [Acta Cryst. (2014), A70, 257-282].

mathematical crystallography

research papers

link to html
The recently classified 3-periodic regular apeirohedra and polygonal complexes in space all have well known crystal nets as edge graphs. These nets are determined explicitly.

link to html
The central role of bounded automorphisms of finite order in non-crystallographic nets is featured; it is shown that stable nets are crystallographic nets.

link to html
The basic tools commonly used to describe the atomic structures of quasicrystals are presented, with a specific focus on the icosahedral phases.


research papers

link to html
Direct methods applying to protein diffraction data below atomic resolution are described. Typical examples for SAD phasing, model completion and phase extension are given in detail.

link to html
An indicator of systematic errors based on theoretical R values is introduced and applied to charge-density data.

link to html
By considering the scattering distributed throughout space, there is an intensity enhancement at the Bragg angle even when the Bragg condition is not satisfied. This leads to an alternative explanation for the diffraction from powders and small crystals.

link to html
The whole set of rigid unit modes in tetragonal tetragonal bronze lattices is described. Structural distortions induced by condensation of the modes are discussed. Confrontation with available experimental data confirms the relevance of the rigid unit mode model.

link to html
Agreement factors based on the ratio of intensities R collected in dynamic structure pump–probe crystallography experiments are shown to be analogous to the {\cal R} factors widely used in standard crystallographic refinements. Fourier photodifference maps allow the visualization of the externally induced structural changes in the crystal, but also can be used during refinement to monitor its progress. Photodeformation maps are modified to separate the photo-induced structural change from the effect of the temperature increase on laser exposure.

international union of crystallography

link to html
The Seitz notation for symmetry operations adopted by the Commission on Crystallographic Nomenclature as the standard convention for Seitz symbolism of the International Union of Crystallography is described.

book reviews

Acta Cryst. (2014). A70, 308
doi: 10.1107/S2053273314000266
Follow Acta Cryst. A
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds