UNUSUAL PROPERTIES OF CUBANE. Synthesized first in 1964, cubane (C₈H₈) is a molecule consisting of 8 carbon atoms arranged at the corners of a cube plus single hydrogen atoms sprouting symmetrically from each carbon (see the figure at Physics News Graphics). The C-C-C bond angle is therefore 90 degrees, rather than the 109.5 degrees customary in other hydrocarbon molecules. Because of this a great deal of strain energy is stored in the chemical bonds---150 kcal/mole or 6.5 eV per molecule. Replace all the H's with NO₂ groups and you get a terrific fuel or explosive (with nearly twice the power of TNT). Replacing the H's with other chemical groups results in potentially more salubrious derivatives, some of which are currently undergoing tests in the fight against the AIDS virus, bone marrow cancer, and Parkinson's disease. For all its potential, however, solid cubane is not well understood. Like other molecular solids (materials such as C₆₀ in which molecules rather than atoms compose the underlying lattice), cubane exhibits a "plastic phase" (close to its melting point) in which the molecules start to swivel about one or more of their axes. Recently, a Chicago-NIST collaboration has experimentally worked out the structure of this plastic phase by sending x rays and neutrons through powdered samples. Surprisingly, unlike most other molecular solids, the plastic phase of cubane is not cubic. The researchers' work includes a model of the intermolecular interactions that correctly predicts this structure, which could speed up future applications of this novel molecule. (T. Yildirim et al.,upcoming article in Physical Review Letters. Contact Peter Gehring at NIST, peter@rrdstrad.nist.gov, 301-975-3946. Journalists can obtain copies of the article from physnews@aip.acp.org)