Nespolo Massimo, Aroyo Mois I
Université de Lorraine, CRM2, UMR 7036, Vandoeuvre-lès-Nancy 54500, and CNRS, CRM2, UMR 7036 Vandoeuvre-lès-Nancy 54506, France.
Física de la Materia Condensada, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado 644, Bilbao, 48080, Spain.
Acta Crystallogr A Found Adv. 2016 Sep 1;72(Pt 5):523-38. doi: 10.1107/S2053273316009293. Epub 2016 Jul 15.
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.
《晶体学国际表》A卷是空间群信息的参考资料。然而，其内容并不详尽，因为对于许多空间群，可以选择多种设置，但并非所有设置都有详细描述甚至完整列出。当目的只是描述晶体结构时，使用替代设置似乎是不必要的复杂情况；然而，这些设置对于许多任务至关重要，例如研究多晶型物或衍生结构之间的结构关系、研究赝对称及其潜在后果以及分析孪晶的公共子结构。本文的目的有两个：(i) 提供一个指南，用于在替代设置中表达空间群的对称操作、赫尔曼-莫古因符号和魏科夫位置；(ii) 指出《晶体学国际表》A卷未列出但可能具有实际应用的空间群的替代设置。
