: a computer tool at the Bilbao Crystallographic Server for the study of pseudo-symmetric or distorted structures.

is a free online program at the Bilbao Crystallographic Server (https://www.cryst.ehu.

Layer groups: Brillouin-zone and crystallographic databases on the Bilbao Crystallographic Server.

The section of the Bilbao Crystallographic Server (https://www.cryst.ehu.

The site-symmetry induced representations of layer groups on the Bilbao Crystallographic Server.

The section of the Bilbao Crystallographic Server (http://www.cryst.ehu.

The crystallographic chameleon: when space groups change skin.

Volume A of International Tables for Crystallography is the reference for space-group information. However, the content is not exhaustive because for many space groups a variety of settings may be chosen but not all of them are described in detail or even fully listed. The use of alternative settings may seem an unnecessary complication when the purpose is just to describe a crystal structure; however, these are of the utmost importance for a number of tasks, such as the investigation of structure relations between polymorphs or derivative structures, the study of pseudo-symmetry and its potential consequences, and the analysis of the common substructure of twins.

Seitz symbols for crystallographic symmetry operations.

The aim of this report is to describe 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. The established notation follows the existing crystallographic conventions in the descriptions of symmetry operations.

Brillouin-zone database on the Bilbao Crystallographic Server.

The Brillouin-zone database of the Bilbao Crystallographic Server (http://www.cryst.ehu.

Apparently complex high-pressure phase of gallium as a simple modulated structure.

The phase of gallium GaII, with symmetry C222(1) and 104 atoms per unit cell, has been recently reported as an example of structural complexity under high pressure. It is shown here that this phase is a simple modulated distortion of an average structure of Fddd symmetry with all atoms structurally equivalent. The modulation can be described with only 4 parameters and satisfies symmetry properties described by a centrosymmetric superspace group.

Bilbao Crystallographic Server. II. Representations of crystallographic point groups and space groups.

The Bilbao Crystallographic Server is a web site with crystallographic programs and databases freely available on-line (http://www.cryst.ehu.