W0006

Crunch, Direct Methods with a Difference. RAG De Graaff, Biophysical Structural Chemistry, L.I.C., University of Leiden, Leiden ZH, 2300 RA The Netherlands

The first practical application is presented of Karle-Hauptman matrices in direct methods of structure determination. The advantage of this approach above conventional methods based on the triplet or quartet relations is the phasing of a largish number of phases concurrently, by (almost) all possible relations between the reflections involved. The models obtained are extended to the full structure in a fully automatic way. The program is designed for solving the phase problem in difficult and/or larger equal atom structures.

Recent developments will be discussed, which are not yet implemented in the version of Crunch distributed via the Internet. For non-commercial users Crunch is available free of charge, members of a commercial institution which are interested in the program are requested to contact the author.