C10. Commission on Structure and Dynamics of Condensed Matter

Report to the 1999 General Assembly for 1996-99

Officers 1996-1999:

Chairman: R. Klein, Germany
Vice Chairman: K. Ando, Japan
Secretary: P. Monceau, France

Members:

K.S. Alexandrov, Russia
J. Bohr, Denmark
C. Di Castro, Italy
J. Hafner, Austria
K.H. Lee, Korea
C.A. Murray, USA
K. Parlinski, Poland
E.C. Svensson, Canada
T.T. Tsong, Taiwan

Activities

Commission C10 on the Structure and Dynamics of Condensed Matter covers a broad area of physics. Accordingly IUPAP has sponsored, following the recommendations of the Commission, a total of eight international conferences since the 1996 General Assembly on various aspects of condensed matter physics. In 1997 the sponsored conferences were the International Conference on Neutron Scattering in Toronto, Canada, the 9th International Conference on Ferroelectricity in Seoul, Korea, and the 11th International Conference on Dynamical Process in Excited States of Solids in Mittelberg, Germany.

In 1998 the Commission sponsored the 9th International Conference on Phonon Scattering in Lancaster, United Kingdom, the 3rd International Conference on Excitonic Processes in Condensed Matter in Boston, USA, and the 11th International Conference on Hyperfine Interactions in Durban, South Africa.

For 1999 the Commission is sponsoring an International Conference on Luminescence and Optical Spectroscopy of Condensed Matter in Osaka, Japan, and the 6th International Conference on the Structure of Surfaces in Vancouver, Canada.

A good geographical diversity of the conference sites can be observed, although Eastern Europe is not represented during this period. Most of the sponsored conferences are by now well established; they reflect the enduring importance of the respective scientific fields.

New Developments

Many of the research activities in the areas of condensed matter physics covered by the Commission are devoted to the characterization of the structure of very different kinds of materials, the identification of their excited states, either of electronic, ionic or molecular character, and the often complex relaxation of these states. The materials considered are in many cases disordered, mesoscopic and surface dominated systems. This trend away from the perfect crystalline materials towards the study of much more complex systems is growing. These systems can be as diverse as metallic, semiconducting or insulating disordered solids or complex fluids consisting of large polymeric molecules. This trend is driven on the one hand by the need for the basic understanding of the fundamental properties directly connected to the disorder or the finite size of a system, and on the other hand by demands to design materials having certain desired properties for technological applications. The properties are often strongly determined by the fact that most atoms or molecules of the system are at or very near to surfaces or interfaces. Adsorbates on smooth or laterally structured surfaces and thin films are important for many applications, and the development of techniques to artificilly structure a surface on a sub-micrometer scale and the understanding of growth mechanisms of adsorbates on such surfaces and of their resulting structures are challenging problems. This area of surface and interface physics is very lively and growing.

Particular examples of disordered materials which are actively studied, are sandpiles and powders, or more generally speaking granular materials. These systems have properties which are determined by an interplay of different characteristic length scales and they have rather unexpected properties which are neither characteristic of solids nor of fluids.

Many advances in the present understanding of the structure and dynamics of condensed matter have been made by scattering experiments with thermal neutrons and synchrotron radiation. These experiments are performed at large-scale facilities, often by small groups from universities or industrial laboratories. The demand for such experiments at multi-user facilities is growing. Besides the significance of these experimental methods for basic research in physics to obtain the atomic and electronic structure and the elementary excitations of solids and liquids, there is an increasing demand from neighboring sciences such as physical chemistry, biology and materials science to use these techniques to solve problems relevant to their fields.

It is therefore necessary that a sufficient number of large-scale facilities for neutron and X-ray scattering are available in the future. However, many of the present neutron sources are nearing the end of their useful lives and thus must be either upgraded or phased out. In view of this expected future neutron gap a meeting was arranged in March 1998 which was attended by representatives of IUPAP Commissions in various areas of condensed matter physics, the chairs of the neutron scattering associations of Europe, the U.S. and Japan and by a spokesman for the OECD Megascience Forum Working Group on Neutron Sources. The current situation concerning the existing sources and the planning of their upgrading and of future sources was discussed and recommendations were formulated. The IUPAP Council has decided that this kind of meeting continue on an experimental basis to discuss issues including the need for new sources, upgrades to excisting sources, availability, access, instrumentation requirements, long range planning and international coordination.

Rudolf Klein, Chair