B14(2+): a magic number double-ring cluster.

B(20) is a "magic number" cluster with double-ring structure. Surprisingly, we also find that B(14)(2+) is a "magic number" cluster with double-ring structure, which has the largest HOMO-LUMO gap (3.31 eV) and the highest aromaticity in double-ring clusters. This double-ring B(14)(2+) cluster is energetically lower than the quasi-planar one by even ∼1.2 eV using high level ab initio calculations. B(14)(2+) also has 40 valence electrons as in Al(13)(-) cluster. The reason leading to the unusual properties of B(14)(2+) may be the electronic shell closing as in Al(13)(-) cluster based on the jellium model, besides the double aromaticity in all double-ring clusters.