Summer 2001 -- Vol. 18, No. 2

FACES OF PENN STATE

A. Welford Castleman Jr.
Evan Pugh Professor of Chemistry and Physics and
Eberly Family Distinguished Chair in Science

A. Welford Castleman Jr. studies small clusters, groups of molecules, as the basis for his materials-science research. One of his projects includes using those clusters as building blocks for a new periodic table.

For A. Welford Castleman Jr., almost everything begins in a small cluster and eventually branches out in many directions. Certainly that approach defines his research. With small clusters of molecules as the basis, he examines many different systems and studies one central issue.

“The interesting thing to me is why systems that are small behave differently from systems that are large,” Castleman says. “Anything we can cluster together to try to understand that mystery, we do.”

With his research regarding clusters of materials, and his broad definition of materials science, Castleman finds many connections for his efforts. Along with his pure materials work, he has made contributions in areas such as atmospheric and environmental chemistry. Still, materials science remains his primary interest and two projects especially pique his curiosity. Metallo-carbohedrenes, or Met-Cars, are one of these. A Castlemen-led group created the first Met-Cars, a combination of carbon and metal atoms, in 1992 and expected them to have applications as catalysts, superconductors, or the quantum wells in superconductor devices.

“It has been a difficult problem,” Castleman says. “We can create the Met-Cars, but either not in enough quantity or, when they are abundant, they’re embedded with other materials that make them difficult to study. Many people are pursuing answers to those problems, though, and it’s only a matter of time before we make more progress toward their isolation in bulk quantities and applications.”

With his other project, Castleman might help devise a whole new periodic table. Again using clusters, he hopes to make alloys that would mimic various atoms across the periodic table and allow for the formation of new materials. With those clusters as the building blocks, he believes scientists could assemble materials that maintain the properties of the individual clusters even after assembly. He believes the approach could lead to the potential formation of new materials tailored for specific uses.

Because of his commitment to education and research, Castleman’s career has branched out through the years as well. He is a member of the National Academy of Sciences and his contributions outside the laboratory—as an editor of numerous journals and an active member of the departments of chemistry and physics—rival his accomplishments as a researcher.

His interest in small clusters and his practice of utilizing them as teaching tools when dealing with students in his lab might help account for at least some of his productivity and prowess at Penn State. He has nine groups in his lab and dedicates two hours every day to meet with an individual group. He meets every group at least once during a two-week span and keeps himself closely connected with his lab work despite the numerous other responsibilities that demand the attention of a senior faculty member.

-- By Steve Sampsell

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