Structural Evolution and Electronic Properties of Two Sulfur Atom-Doped Boron Clusters

[Image: see text] We present a theoretical study of structural evolution, electronic properties, and photoelectron spectra of two sulfur atom-doped boron clusters S(2)B(n)(0/–) (n = 2–13), which reveal that the global minima of the S(2)B(n)(0/–) (n = 2–13) clusters show an evolution from a linear-chain structure to a planar or quasi-planar structure. Some S-doped boron clusters have the skeleton of corresponding pure boron clusters; however, the addition of two sulfur atoms modified and improved some of the pure boron cluster structures. Boron is electron-deficient and boron clusters do not form linear chains. Here, two sulfur atom doping can adjust the pure boron clusters to a linear-chain structure (S(2)B(2)(0/–), S(2)B(3)(0/–), and S(2)B(4)(–)), a quasi-linear-chain structure (S(2)B(6)(–)), single- and double-chain structures (S(2)B(6) and S(2)B(9)(–)), and double-chain structures (S(2)B(5), and S(2)B(9)). In particular, the smallest linear-chain boron clusters S(2)B(2)(0/–) are shown with an S atom attached to each end of B(2). The S(2)B(2) cluster possesses the largest highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap of 5.57 eV and the S(2)B(2)(–) cluster possesses the largest average binding energy E(b) of 5.63 eV, which shows the superior chemical stability and relative stability, respectively. Interestingly, two S-atom doping can adjust the quasi-planar pure boron clusters (B(7)(–), B(10)(–), and B(12)(0/–)) to a perfect planar structure. AdNDP bonding analyses reveal that linear S(2)B(3) and planar SeB(11)(–) have π aromaticity and σ antiaromaticity; however, S(2)B(2), planar S(2)B(6), and planar S(2)B(7)(–) clusters have π antiaromaticity and σ aromaticity. Furthermore, AdNDP bonding analyses reveal that planar S(2)B(4), S(2)B(10), and S(2)B(12) clusters are doubly (π and σ) aromatic, whereas S(2)B(5)(–), S(2)B(8), S(2)B(9)(–), and S(2)B(13)(–) clusters are doubly (π and σ) antiaromatic. The electron localization function (ELF) analysis shows that S(2)B(n)(0/–) (n = 2–13) clusters have different electron delocalization characteristics, and the spin density analysis shows that the open-shell clusters have different characteristics of electron spin distribution. The calculated photoelectron spectra indicate that S(2)B(n)(–) (n = 2–13) have different characteristic peaks that can be compared with future experimental values and provide a theoretical basis for the identification and confirmation of these doped boron clusters. Our work enriches the new database of geometrical structures of doped boron clusters, provides new examples of aromaticity for doped boron clusters, and is promising to offer new ideas for nanomaterials and nanodevices.