Structure of boron clusters revisited, Bn with n = 14-20

We reinvestigate the structures of neutral boron clusters Bn, with n = 14-20. G3B3 calculations confirm that a transition between 2D and 3D shape occurs at B20, which has a tubular form. In disagreement with Boustani et al. (Phys. Rev. B, 83 (2011) 193405), we find a planar B19 cluster. Standard heats of formation are obtained and used to evaluate the clusters stability. The average binding energy tends to increase with increasing size toward a limit. Higher stability is found B14, B16, B18 and B20. All Bn have negative NICS-values. The bonding nature and electron delocalization of B20 are re-examined using CMO and LOL.

120Highlights► The Bn clusters with n = 14-19 are planar structures. ► In disagreement with a recent report by Boustani et al., we find that the B19 cluster is planar. ► The transition between 2D and 3D structure occurs at the B20 that is a tubular form with highly aromatic feature. ► All neutral Bn clusters have aromatic character.