Structures and stability of B-doped Al anions: AlnB− and AlnB2− (n = 1–7)

Various structural possibilities for AlnBm− (m + n = 3–8, m = 1–2) anionic isomers were investigated using B3LYP/6-31+G(d) and CCSD(T)/6-31+G(d) methods. Our calculations predicted the existence of a number of previously unknown isomers. All structures of the AlnB− (n = 2–6) may be derived from a substitution of an Al atom by a B atom in the Aln+1− anions while the geometrical structure of Al7B− may be understood as putting centrally a B atom inside the Al7− cage-like structure. The strong BB bond is dominant factor in building-up principle of mixed AlnB2− (n = 1–6) anions. All AlnBm− with odd n + m (2 < n + m < 9) are relatively more stable. Our present results satisfactorily explain the photoelectron spectroscopy and finally improve our understanding of these experimental observations.