What is the most stable B24N24 fullerene?

B3LYP/6-31G* density functional theory calculations have been carried out on the structure and stability of seven B24N24 clusters. It is found that the new proposed isomer with two octagons, sixteen hexagons and eight squares in S8 symmetry is more stable than the isomer with six octagons, eight hexagons and twelve squares in O symmetry by 60.4 kcal/mol, and the isomer with twenty hexagons and six squares in S4 symmetry by 2.8 kcal/mol. The fullerene-like isomer is much higher in energy (148.6 kcal/mol).