BeB cluster: a dynamically fluxional beryllo-borospherene.

The beryllium-doped BeB cluster has two nearly isoenergetic isomers, adopting the smallest trihedral spherical geometries with a boron single-chain skeleton. The B skeleton in the global minimum (, A) comprises three conjoined boron rings (one B/two B) on the waist, sharing two B equilateral triangles at the top and bottom, respectively. However, the local minimum (, A') has one deformed B pyramid at the top. The drastic structural transformation of B skeletons from perfectly planar B clusters mainly profited from robust electrostatic interaction between Be atoms and B skeletons. The dynamic simulations suggest that two species can interconvert a novel mechanism, that is "triangle-pyramid-triangle", which facilitates the free migration of boron atoms in the B skeleton, thereby showing the fascinating dynamic fluxionality. The chemical bonding analyses reveal that the B skeleton is covered by two types of delocalized π bonds in an orthogonal direction, which leads to its spherical aromaticity.