Boron aggregation in the ground states of boron-carbon fullerenes

We present novel structural motifs for boron-carbon nano-cages of the stochiometries B12C48 and B12C50, based on first principle calculations. These configurations are distinct from those proposed so far by the fact that the boron atoms are not isolated and distributed over the entire surface of the cages, but rather aggregate at one location to form a patch. Our putative ground state of B12C48 is 1.8 eV lower in energy than the previously proposed ground state and violates all the suggested empirical rules for constructing low energy fullerenes. The B12C50 configuration is energetically even more favorable than B12C48, showing that structures derived from the C60 Buckminsterfullerene are not necessarily magic sizes for heterofullerenes.