Structure and stability of B₈ clusters

We investigated various isomers of B₈ clusters with ab initio (MP2) and density function theory (DFT) methods (B3LYP and B3PW91). Nineteen B₈ isomers were determined to be local minima on their potential energy hypersurfaces by the B3LYP, B3PW91, and MP2 methods. Fifteen of these structures are first reported. The most stable neutral B₈ cluster is the regular heptagon, with another boron atom at the center (D_7h, triplet), in agreement with results reported previously. The natural bond orbital (NBO) analysis and nucleus-independent chemical shifts (NICS) further reveal that the most stable species have delocalized π bond and multicentered π bonds and therefore exhibit multiple-fold aromaticity.