INTRODUCTION TO THE CIF CORE DEFINITIONS. I.D.Brown, Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada L8S 4M1

The original cif core dictionary (Hall, Allen and Brown, 1991) defined cif names for the basic crystallographic quantities, so that cifs could be used to report small molecule crystal structures to Acta Crystallographica C. The dictionary is now in routine use for the submission of structure reports to Acta Cryst. B and C and is being widely incorporated into crystallographic software.

The cif core definitions have proved to be quite robust despite the remarkable changes that have occurred in the philosophy of the crystallographic information file in the intervening years. Some weaknesses in the definitions have been identified and these will be addressed in the extension to the core cif dictionary which is in an advanced stage of preparation.

As of the beginning of 1996 the core cif dictionary is the only one that has been approved, but the core extension is expected to receive approval during 1996.

Hall, S.R., Allen, F.H. & Brown, I.D. (1991) Acta Cryst. A47, 655- 685.