This award supports Professor James P. Sethna and members of his research group at Cornell University to collaborate in applied physics research with Professors Karsten W. Jacobsen and Jens Norskov, Laboratory of Applied Physics, Technical University of Denmark, Lyngby, Denmark. In this Danish laboratory, major theoretical and experimental efforts are being pursued to explore ion and molecular scattering at surfaces. Professor Sethna is developing an interactive, modular system for studying molecular dynamics and scattering on surfaces. Together with his hosts in Denmark, Professor Sethna will generalize his molecular dynamics package to be useful in the new experimental systems at the Danish laboratory. In addition, he is working on a user interface for electronic structure calculations. This is an area where the Danish group is also quite active, and where joint effort will be productive and mutually beneficial. Dr. Sethna will also collaborate with Professors John Hertz, Alan Luther and others at Nordita (The Nordic Institute for Theoretical Physics, located in Copenhagen) on a variety of topics in condensed matter theory, including critical phenomena of disordered and glassy systems. Professor Sethna's research for the past few years has been primarily in the area of liquid crystals and glass transition. His research plans for his sabbatical will expand his work more actively into surface phenomena. The enhanced and bench tested software programs he hopes to complete in partnership with Danish collaborators will have wide applications in a variety of laboratory settings.