'Buckyball' II: the game continues.

In just a few months, the newly discovered moecule C.sub.60 -- buckminsterfullerene, or "buckyball" for short -- has become the center of a wide range of theoretical and laboratory investigations (SN: 11/23/85, p. 325). This molecular appears to have a geometric structure like the pattern on a soccer ball. Its high degree of symmetry indicates that the molecule is probably quite stable and may have some unusual properties.

The molecule, essentially a hollow sphere, has a diameter of about 7 angstroms. This provides an inner cavity that may be large enough to hold various atoms. Reporting in the Dec. 11 JOURNAL OF THE AMERICAN SOCIETY SOCIETY, a group of chemists now says it has evidence for the formation of a stable complex consisting of a single lanthanum atom surrounded by a C.sub.60 carbon shell.

In their experiments, chemist Richard E. Smalley and his colleagues at Rice University in Houston used a laser to vaporize spots on a graphite disk impregnated with lantanum ions. The ejected carbon clusters were ionized and carried in a stream of helium gas through a mass spectrometer. The resulting measurements showed the presence of various carbon clusters, several of which included a single lanthanum atom. None of the clusters appeared to pick up a second metal atom.

There's room inside the molecule for atoms as large as uranium, says Smalley. "It's incredible that there should be a stable molecule with such a large vacuum inside," he says. "It's like a little, portable vacuum system." The chemists are finding that some atoms, such as calcium, are easy to get inside the carbon spheres, but others, such as iron, don't seem to fit in very well.

If a way can be founded to synthesize C.sub.60 molecules on a large scale, then "the chemical and practical value of the substance may prove extremely high," the researchers say. "It would be a very bizarre substance," adds Smalley. A mass of uranium-containing buckyballs, for instance, would be as easy to cut as butter. Compounds like C.sub.60.f.sub.60., if they can be created, may be "superlubricants." However, no one yet knows how stable the molecules would be when two or more come together.

Nevertheless, buckyballs could be created under the violent conditions that accompany exploding carbon-rich stars. These cosmic soccer balls could be sites for chemical processes leading to the formation of interstellar molecules. The researchers also speculate that this especially stable and symmetrical carbon structure provides a possible catalyst or intermediate in the chemical processes that led to the origin of life on earth.

Recent results suggest that many carbon clusters containing an even number of atoms, from 40 to beyond 80, are also relatively stable and remarkably unreactive. They, too, may be closed spheroidal shells, says Smally. C.sub.70., for instance, probably incorporates an extra band of hexagons to give the molecule an egg-shaped structure.

"The more we think about it," says Smalley, "the more we think this has a lot to do with the mechanism for the generation of soot." Soot particles tend to be spherical. Each one may have a buckyball at its core.

Theoretical chemist A.D.J. Haymet of the University of California at Berkeley suggests that the molecule C.sub.120 may also be stable. Like C.sub.60., it is highly symmetrical. However, the carbon atoms at each vertex are not in identical environments, says Smalley, but in mirror-image arrangements.

"Every day there's a new thing to puzzle over, wonder about or think of," says Rice's Robert F. Curl. "It's really been exciting. It captures the imagination because the symmetry is so beautiful."