Polyhedra, complexes, nets and symmetry

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.

Non-crystallographic nets: characterization and first steps towards a classification

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

Atomic clusters and atomic surfaces in icosahedral quasicrystals

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

Applications of direct methods in protein crystallography for dealing with diffraction data down to 5 Å resolution

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.

About systematic errors in charge-density studies

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

A new theory for X-ray diffraction

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.

Unified approach for determining tetragonal tungsten bronze crystal structures

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.

On the assessment of time-resolved diffraction results

Agreement factors based on the ratio of intensities R collected in dynamic structure pump–probe crystallography experiments are shown to be analogous to the 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.

Seitz symbols for crystallographic symmetry operations

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.

Notes for authors

Quasicrystals. A Primer