The boron buckyball has an unexpected Th symmetry

Abstract

The boron buckyball avoids the high symmetry icosahedral cage structure.The previously reported I h symmetric structure is not an energy minimum in the potential energy surface and exhibits a spontaneous symmetry breaking to yield a puckered cage with a rare T h symmetry. The HOMO-LUMO gap is twice as large as the reported value and amounts to 1.94 eV at B3LYP/6-31G(d) level. The valence orbital structure of boron buckyball is identical to the one in the carbon analogue.

Exploring at nanoscale from first principles

“…Its stability was further confirmed by comparing its cohesive energy with that of boron double rings, whose existence has been verified experimentally. Further calculations found that the I h B 80 cage has seven imaginary frequencies and exhibits a spontaneous symmetry breaking to achieve even lower energy [24,25]. In another work, Prasad and Jemmis studied a B 84 cluster that is a basic unit of bulk β-boron and found that it is deficient by 50 electrons according to the Wade-Mingos rule.…”

Cubic Icosahedra? A Problem in Assigning Symmetry

“…Cs 3 C 60 has a structure (26) that can be described using Figure 1, where the unit cell has C 60 units at the cube corners and at the bodycenter, and the Cs ions are at the corners of the icosahedron, so that both the C 60 units and the icosahedron have T h rather than I h symmetry. Cubic distortions from I h to T h symmetry have been predicted for the hypothetical molecules B 80 , Si 60 , and Ge 60 (27,28), and T h symmetry can be found experimentally in appropriately substituted fullerenes (29). In "octahedral" symmetry, T h occurs in hexa-coordinated complexes ML 6 , where L has a local C 2v symmetry, and the principal ligand planes include the heavy lines of Figure 2.…”

10.3726/978-3-653-04937-4/14

“…Later it has been defended that the geometry of the most stable structure seems to be a slight distortion of the I h configuration. Both Gopakamur et al [255,256] and Baruah et al [257] have further investigated the stability of the lowest energy isomers of B 80 , and claim that the icosahedral structure is unstable; the ground state configuration is reported to have, in fact, T h symmetry. However, the recent work of Sadrzadeh et al [258] has also investigated the issue, and report very small energy differences (lower than 30 meV) among the three lowest lying isomers (I h , T h , and C 1 ), with the icosahedral shape being, in fact, a close winner.…”