Meeting report

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Commission on crystallographic nomenclature

The Commission on Crystallographic Nomenclature comprises an elected Chairperson and ex officio members, namely the editors of the Union’s journals and International Tables, the Chairman of the IUCr/OUP Book series Committee, the Chairman of the Teaching Commission, the Chairman of the Committee for the Maintenance of the Crystallographic Information File Standard, the President and the General Secretary of the IUCr. After the retirement of its past Chairman, Sidney Abrahams, André Authier was elected as the new Chairman.

Nomenclature problems arising in specific fields of crystallography are studied by ad hoc committees of experts appointed by the Commission.

The Second Report of the Subcommittee on the Nomenclature of n-Dimensional Crystallography, chaired by T. Janssen, has been accepted by the Commission, and will shortly be printed in Acta Crystallographica, Section A.

[CCN members] Members of the Commission on Crystallographic Nomenclature (left to right: Å. Kvick (France), G. Ferguson (Canada), D. Mills (USA),K. El Sayed (Egypt), T. Hahn (Germany), D. Litvin (USA), F. Allen (USA), S.R. Hall (Australia), C.P. Brock (USA), B. McMahon (UK), I.D. Brown (Canada), D. Schwarzenbach (Switzerland), W. Clegg (UK), J.P. Glusker (USA), U. Shmueli (Israel), A. Authier (France).
The present working groups are:

  • 'Working group on the definition of crystalline phase identifiers', chaired by I.D. Brown, charged with generating machine-readable forms of identifiers suitable to uniquely characterise crystalline phases reported in electronic databases, in line with the IUPAC/CODATA/ICSTI project to standardise the representation of physicochemical properties led by H. Kehiaian. An early conclusion of the working group is that it is useful to work with multiple-component identifiers (in the spirit of the recommendations of the Phase Transition Nomenclature subcommittee). Early proposals are defining possible components by the use of data fields in CIF notation. The final form of an identifier will not necessarily be a collection of CIF data items, and alternative but equivalent representations might be appropriate for different purposes.
  • 'Working group on co-crystal nomenclature' chaired by F. Allen. This group arose from an observation by Professor J. Dunitz that there is no systematic nomenclature in general for the large variety of multi-component solid-state systems. A nomenclature to differentiate and define such systems could be applied to examples as diverse as inclusion compounds, supramolecular complexes, addition compounds, zeolites, solvates, racemic compounds etc. The working group will study any existing IUPAC recommendations and practices, and will work closely with IUPAC on this topic.
  • 'Working group on synchrotron radiation nomenclature' chaired by D. Mills. An example of nomenclature problems is given by the existing confusion between the uses of the terms 'brilliance' and 'brightness'.
  • Crystallographers are invited to bring additional nomenclature problems to the attention of any Commission member.

The Nomenclature Commission web page is currently being revised. The draft new web page can be consulted at

André Authier