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.