Geometry and electronic structures study of rare earth-doped boron-based clusters: REB_n^- (RE = La, Sc; n = 6, 8)

Abstract

Rare earth doped boron clusters have attracted much attention due to their special optical, electrical and magnetic properties. The geometric structure, stability, electronic properties and aromaticity of negative rare earth doped boron clusters REB_n^- (RE = La, Sc; n = 6, 8) are investigated with the artificial bee colony algorithm combined with density functional theory (DFT) calculations at the PBE0/RE/SDD//B/6-311+G^* level of theory. Calculations show that the ground state structures of REB_n^- (RE = La, Sc; n = 6, 8) are all C₂ symmetry, and the doped lanthanide atom is located in the “boat-shaped” structure with the top center. By comparing with the experimental photoelectron spectroscopy, it is confirmed that the ground state structure of LaB₈^- is a “zither-like” three-dimensional structure, and the ground state structure of ScB₈^- is an “umbrella” structure with C_<i>7V</i> symmetry formed by the scandium atom at the “umbrella handle”. The electron localization between RE-B is inferior to that between B-B. The simulated photoelectron spectra have similar spectral characteristics with the experimental results. The lowest energy structures of LaB₆^- and ScB₆^- are σ-π double aromatic clusters, and the structures exhibit aromaticity. The density of states of low-energy isomers shows that the open shell ScB₈^- density of states spectrum exhibits spin polarization phenomenon, which is expected to assemble magnetic material elements. These studies are helpful to understand the evolution of the structure and properties of nanomaterials and provide important theoretical support for the design of nanomaterials with practical value.