Lithium doped tubular structure in LiB20 and LiB20−: a viable global minimum

Abstract

We present a strategy by which the stability of tubular boron clusters can be significantly enhanced by doping the B₂₀ cluster with a lithium atom. High-level quantum chemical calculations showed that the lowest energy structures of LiB₂₀ and LiB₂₀⁻ are tubular structures with D_10d symmetry, in which the lithium atom is located at the center of the tubular structure. Chemical bonding analysis revealed that the high-symmetry tubular boron clusters are characterized as charge transfer complexes (Li⁺B₂₀⁻ and Li⁺B₂₀²⁻), resulting in double aromaticity with delocalized π + σ bonding and strong electrostatic interactions between cationic Li⁺ and tubular boron motifs with twenty Li–B interactions. The unique bonding pattern of the LiB₂₀ and LiB₂₀⁻ species provides a key driving force to stabilize tubular structures over quasi-planar structures, suggesting that electrostatic interactions resulting from alkali metals might unveil a new clue to the structural evolution of boron clusters.