June 2006 Archives

Scientists at North Carolina State University, USA recently published an interesting report on the significance of the anomalously high concentration of local Ge-Ge bonds in amorphous Ge₂Sb₂Te₅, which is commonly used in data storage technologies such as DVD, DVD-RAM etc. The ability to change phases from a crystalline to a non-crystalline state is what allows the DVD to take and hold data. While the basic properties of this alloy are well known, there are still a lot of unsolved problems: we do not know how the process works on a microscopic level. The paper indicates that the amorphous phase is an ideal network structure in which the average number of constraints per atom equals the network dimensionality. For more information, see the paper, ""Application of Bond Constrain Theory to the Switchable Optical Memory Material Ge₂Sb₂Te₅", D. A. Baker et al., Phys. Rev. Lett. 96, 255501 (2006).

Cornell High Energy Synchrotron Source (CHESS) invited researchers from around the world to a series of workshops focused on cutting-edge sciences that will be built up by the proposed Energy Recovery Linac (ERL), which is a next-generation light source. The series of six two-day workshops was held at the Robert Purcell Community Center, Ithaca, NY, USA, between June 5 and June 24. The workshops covered high-pressure science, ultra-fast processes, materials science, studies of soft-matter, biology, and science with X-ray nanobeams. For more information on ERL, visit http://erl.chess.cornell.edu/

A series of very interesting experiments has been performed at beamline ID26 at the European Synchrotron Radiation facility (ESRF), Grenoble, to see how gold nanoparticles catalyze carbon monoxide (CO) with oxygen (O₂) into carbon dioxide (CO₂). High-energy resolution X-ray absorption spectroscopy reveals how the oxygen becomes chemically active when bound to the particles. The reaction took place when the scientists switched from a flow of O₂ to one of CO - the O₂ bound to the gold reacts with the CO to form CO₂. The technique can be applied to a variety of reactions. For more information, see the paper, "Activation of Oxygen on Gold/Alumina Catalysts: In Situ High-Energy-Resolution Fluorescence and Time-Resolved X-ray Spectroscopy", Jeroen A. van Bokhoven et al., Angewandte Chemie, published online June 21, 2006.