Commission on Electron Crystallography


Triennial Report 1990-1993

At the Bordeaux General Assembly in July 1990, the membership of the Commission was re-established to provide as broadly representative a group of members as possible after an unusually great number of mandatory retirements and resignations. A last-minute resignation of the member representing interests in LEED and allied surface analysis techniques required a special later election procedure and the position was filled by M. van Hove in 1991.

The proposal that the Commission should undertake the compilation of a multi-author book on electron diffraction techniques was initiated at the Perth Congress in 1987. After considerable discussion, this project was started in 1988 with a proposed deadline for submission of chapters in final form in 1989. After considerable modifications of the original plans, delays by some authors and expansions of the length and scope of some chapters, the final product is a set of two volumes published by Oxford University Press as part of the IUCr Monographs on Crystallography series. The first volume appeared late in 1992 and the second volume in early 1993. The main emphasis of the books is on the theory, experimental techniques and analytical methods for the determination of the structures of solids by use of high-energy electron diffraction. The principles and practice of electron microscopy are included only to the extent required for understanding the diffraction effects involved. Low-energy electron diffraction and related techniques for studying surface structure are not included, being well documented in other publications, and only one short chapter is devoted to gas electron diffraction. Otherwise, the coverage of electron diffraction techniques is made as complete as seemed reasonably possible.

Following a proposal made at the Bordeaux meeting of the Commission, plans were developed to hold Summer Schools on topics related to electron crystallography. The original intention was for two Schools, one in China and one in Europe, to allow easier access for a larger number of potential students. Because only the China School could receive support as a Satellite Meeting of the IUCr Congress in 1993, the plan for a European School was deferred. The Summer School on `Electron Crystallography - Theory and Practice' will be held in Beijing, during the week immediately preceding the Congress. An international panel of instructors will lead discussions on the use of high-energy electrons to determine structures of gases, amorphous solids, thin crystals of biological, organic and inorganic materials and to determine accurate values for structure factors using dynamical diffraction methods.

A survey of the computer programs being used for the calculation of intensities for high-resolution electron micrographs of crystals and electron diffraction patterns has been initiated and is being coordinated by D. van Dyck, Antwerp. A proposal for sets of calculations to be made as a basis for comparisons of accuracies has been circulated. It is anticipated that the results of the survey will be submitted for publication.

The Commission has been active in preparing proposals to the Programme Committee of the Beijing Congress for special talks and Symposia dealing with electron diffraction and related areas of crystallography.

10 February 1993

J. M. Cowley, Chairman