by Katherine A. Caponi

Playground equipment used to be simpler. Where posh lumber ladders and soft-sided plastic slides now top the woodchip and grass fields of our children's playgrounds, skeletal Catskills of welded metal once towered over dusty gravel. An insurance liability, to be sure, but they had the stark beauty of metal joints and poles forced by fire to form rudimentary castles for schoolyard crowds.

Chemistry and quantum mechanics were once simpler, too. Models built of Styrofoam balls and pipe cleaners--those other staples of elementary school--used to rule the field. Today, computer programs run simulations predicting the behavior of molecules at the quantum level.

The molecules themselves are also more complex. "The last decade has witnessed explosive growth in basic and applied research on inorganic particles," says Steven Lewis, assistant professor of physics at the University of Georgia. "Advances in both theoretical and experimental techniques have resulted in the discovery of a wealth of new stable nanoparticles exhibiting a wide range of novel behaviors."

But there is much to learn about the behaviors and properties of the transition-metal carbide nanoparticles that Lewis and his team study before scientists can begin to turn them into useable materials for industry. Transition metals are the chemical elements occupying the skinny middle section of the Periodic Table. They are very chemically active and exhibit a wide range of physical properties, features that makes them and their compounds appealing to industries such as chemical processing and magnetic data storage.

A particularly interesting feature of the transition metals is that they form a host of different compounds when paired with other elements. One such family of compounds is transition-metal carbides (TMCs), which have many industrially important uses. When researchers combine energetic transition-metal and carbon atoms in a on-to-one ratio in the gas phase, they form very stable crystalline formations called nanocrystals. TMC nanocrystals are structurally similar to rock salt--a cubic-shaped crystal forming a 3D checkerboard of atoms. What is so unusual is that they retain this crystalline for even for particles containing only two-dozen or so atoms. Using Alliance supercomputers, the team analysed the electronic structure of titanium carbide nanocrystals to provide theoretical understanding for recent puzzling experimental findings.

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Access Online | Posted 2-24-2004