B-38: an all-boron fullerene analogue

Fullerene-like structures formed by elements other than carbon have long been sought. Finding all-boron (B) fullerene-like structures is challenging due to the geometrical frustration arising from competitions among various structural motifs. We report here the prediction of a B-38 fullerene analogue found through first-principles swarm structure searching calculations. The structure is highly symmetric and consists of 56 triangles and four hexagons, which provide an optimal void in the center of the cage. Energetically, it is more favorable than the planar and tubular structures, and possesses an unusually high chemical stability: a large energy gap (similar to 2.25 eV) and a high double aromaticity, superior to those of most aromatic quasi-planar B-12 and double-ring B-20 clusters. Our findings represent a key step forward towards to the understanding of structures of medium-sized B clusters and map out the experimental direction of the synthesis of an all-B fullerene analogue.