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Introduction

Chemical formulae in inorganic crystal structure papers often give very little structural information. This is due partly to the existence of several different notations in the literature and partly to the lack of a single generally accepted nomenclature. In addition, relationships between structures, such as isotypism and homeotypism, are described differently.

The Ad hoc Meeting on the Nomenclature of Inorganic Structure Types, sponsored by the IUCr Commission on Crystallographic Nomenclature at the 13th International Congress of Crystallography in Hamburg on 11 August 1984, prompted the Commission to appoint a Provisional Subcommittee to study the problems discussed [see Acta Cryst. (1986). A42, 64 for the Subcommittee membership]. The progress subsequently made at an informal meeting in Lisbon led to recognition of the Provisional Subcommittee as a regular Subcommittee of the Commission on 19 August 1985.

In the present Report, the Subcommittee proposes concise definitions for different degrees of similarity between inorganic structure types and a detailed notation for the coordination of atoms. Basic rules for developing crystal-chemical formulae and Bauverband descriptions are recommended as well. The primary aim is to promote, although not to enforce, the use of crystal-chemical formulae instead of traditional chemical formulae which contain no structural information.

This Report was prepared during four meetings of the Subcommittee, the first held in Lisbon (April 1985), the others in Marburg (February 1986), Geneva (December 1986), and Copenhagen (March 1988). It represents an extension and updating of pioneering concepts on crystal-chemical formulae by Machatschki (1928, 1947, 1953), Bragg (1930) and Bokii (1954), and on lattice complexes by Niggli (1919, 1945), Laves (1930) and Hermann (1960).

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