Structural evolution and electronic properties of doped boron clusters Ta2Bn (n = 10?20): Ta2B16 and Ta2B18 with strong aromaticity

In this work, we combine the CALYPSO method with DFT calculations to conduct a comprehensive structural search of Ta2Bn (n = 10 - 20) clusters. Among all the candidate structures obtained by CALYPSO searching, the structures of ground state Ta2Bn clusters at each size are determined according to their total energy and symmetry. The relative stability analysis indicates that the ground state Ta2B16 and Ta2B18 clusters with the unique bicyclic boron ring and two Ta atoms as axes exhibit excellent stability in the studied range, with their HOMOLUMO gaps of 2.374 and 2.640 eV, respectively. The bonding analyses reveal that the strong interaction between two Ta atoms and the outer B16/18 bicyclic ring dominates their significant stability, especially the interaction between Ta-d AOs and B-s/p AOs. It is confirmed that both Ta2B16 and Ta2B18 have strong aromaticity by examining the isochemical shielding surface (ICSS). Finally, the strong coupling between their outer boron rings (B16/18) and two Ta atoms inside the structures of Ta2B16 and Ta2B18 is further elucidated by the electronic absorption spectrum (UV-vis and CTS).

Automated summary

In this work, a combination of the CALYPSO method and DFT calculations is employed to perform a comprehensive structural search of Ta2Bn (n = 10 - 20) clusters. The ground state structures of Ta2Bn clusters at each size are determined based on their total energy and symmetry. It is found that Ta2B16 and Ta2B18 clusters exhibit excellent stability, with unique bicyclic boron rings and two Ta atoms as axes. The strong interaction between two Ta atoms and the outer B16/18 bicyclic ring is the primary factor contributing to their significant stability.