Methylidyne-replaced boron nitride fullerenes and nanotubes: a wave function study

Abstract

Methylidyne (CH) groups are shown here through ab initio wavefunction computations to strengthen the fullerene cages of the smallest boron nitride fullerenes, B₁₂N₁₂ and B₁₆N₁₆, when a CH replaces a nitrogen atom. Adding the carbon atoms strengthens the stabilization energy of the molecule for up to six CH inclusions in B₁₂N₁₂ and seven for B₁₆N₁₆. Once two CH groups are present on a single four-membered ring in the octahedral structure, the favorable stabilization of the isoelectronic methylidynes is overcome by the steric repulsion of the hydrogen atoms in relatively close proximity. Differently, boron nitride nanotube models are actually destabilized with every CH replacement of a nitrogen. Provided that these replacements are fairly far apart (on the order of two rings away), the decrease in stabilization energy per atom is only less than 0.02 eV. The fullerenes are able to pucker more easily than the nanotubes making their methylidyne favored as opposed to the slight disfavor in the latter set. In either case, the presence of the hydrocarbon(s) in either the fullerene or nanotube framework is a potential application for hydrogen storage and materials development.