  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.
