Symmetry breaking in metamaterials

Abstract

Fullerene-like boron clusters have remained, until now, in the realm of theoretical studies. Now, Lai-Sheng Wang and colleagues report experimental evidence of a fullerene-like molecule for the B 40 anion and for neutral B 40. Laser-vaporization techniques are used to form the clusters that are subsequently separated with a mass spectrometer and characterized using photoelectron spectroscopy. Together with the fullerene-like cluster of B 40-, a quasi-planar isomer is observed, which is slightly more stable than the fullerene-like cluster. However, the fullerene-like cluster of neutral B 40 is much more stable than its corresponding quasi-planar structure. Instead of resembling the football-like structure of carbon-based fullerenes, the all-boron cages have hexagonal holes at the top (pictured) and bottom, and four heptagonal holes along the sides. Chemical bonding analyses of the neutral B 40 suggest all valence electrons are delocalized σ or π bonds. Preliminary calculations indicate that the fullerene-like boron cages could be used for hydrogen adsorption and release, or can be doped with a metal atom. Wang and colleagues have named the all-boron fullerenes 'borospherenes'. AS