title: The crystallographic chameleon: when space groups change skin.
abstract: 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. The aim of the article is twofold: (i) to present a guide to expressing the symmetry operations, the Hermann-Mauguin symbols and the Wyckoff positions of a space group in an alternative setting, and (ii) to point to alternative settings of space groups of possible practical applications and not listed in Volume A of International Tables for Crystallography.
authors: Université de Lorraine, CRM2, UMR 7036, Vandoeuvre-lès-Nancy 54500, and CNRS, CRM2, UMR 7036 Vandoeuvre-lès-Nancy 54506, France.
authors: Massimo
authors: M
authors: Nespolo
authors: Física de la Materia Condensada, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado 644, Bilbao, 48080, Spain.
authors: Mois I
authors: MI
authors: Aroyo
keywords: Hermann–Mauguin symbols; axial setting; space groups