Aromatic cages B420/+: unprecedented existence of octagonal holes in boron clusters

The cage-like structures containing octagonal holes are located as the lowest-lying isomers for the B-42(0/+). The presence of octagonal holes, which have been found for the first time, not only gives us new insight into the bonding motif, but also marks a breakthrough in the structural characteristics of boron clusters since they were never expected to be stable units for elemental clusters. These cages are composed of both delocalized sigma and pi electron systems that consequently make them aromatic and thermodynamically stable.