Commission on Electron Crystallography


Report of 1999 Congress and Commission Meeting

11 August 1999

D. L. Dorset, chair, S. Hovmõller secretary

Before the Congress, a workshop on 'Structure factor phase determination in electron crystallography', organized by S.Hovmõller and J. Gjønnes, was held at the Glasgow Convention Center on 4 August and generated lively discussion about various aspects of crystal structure determination via electron diffraction data.

The Commission sponsored two microsymposia: 'The phase problem in electron crystallography', organized by R. Vincent and D.L. Dorset (5 August) and 'Quantitative electron diffraction and microscopy, organized by D. Van Dyck and J. Gjønnes (11 August). In addition a joint session with the Commission for Powder diffraction, 'Structure solution from powders using electron and powder diffraction techniques' was organized by S. Hovmõller and B. Cernik (13 August).

A number of items were discussed at the Commission meeting, attended by Dorset, Van Dyck, Hovmõller, Li, Gjønnes, and with Jouk Jansen representing Henny Zandbergen. First, Dirk Van Dyck presented the results of a round robin test of software packages for carrying out multiple beam dynamical scattering calculations. With proper controls, the results are found to be equivalent. This work is to be published in Ultramicroscopy. S. Hovmõller suggested a similar standardized study of an inorganic material to determine how various approaches might succeed in determining the correct crystal structure from electron scattering data. While other attendees thought that this may be a less easy task than establishing whether or not a computational package gives useful results, it was agreed that results of such a study might be announced on an expanded web site, linking to various laboratories carrying out such electron crystallographic structure analyses. This suggestion partially answers a suggestion made by Li Fan-hua that a publication discussing procedures for structure analysis in electron crystallography may result eventually (e.g. to supplement the two volume work already published for the IUCr and edited by John Cowley). Obviously, this web site should be linked to the various other laboratory sites.

Jon Gjønnes discussed the topics to be discussed at the upcoming European Crystallographic meeting in Nancy that may result in microsymposia. He and Sven Hovmõller have been charged to form a SIG on Electron Crystallography within the newly formed European Crystallographic Association. Also relevant are the possible topics to be discussed at the upcoming European Microscopy Meeting to be held in Brno, Czech Republic. Dr. Ingrid Voigt-Martin and Dr. John Fryer have been planning sessions and a tutorial on electron crystallography. In general, there is a need to improve communications between microscopy and crystallographic societies, particularly if both purport to represent and promote research in electron crystallography.