Structure, bonding, and stability of small boron-lithium clusters

Structures and energies for BLi_n (n = 1-3) are investigated with various basis sets and with different levels of theory, including single reference- and multireference-based correlated methods up to QCISD(T)/6-311+G-(3df)//MP2(full)/6-311+G(d), MCQDPT2/6-311+G(2df)// CASSCF/6-31G(d), G2, and G2(MP2) theory. BLi (³Π_g), BLi₂ (²B₂), and BLi₃ (C_2v) are global minima with respective atomization energies of ∼26, 55, and 95 kcal/mol. Their structures are not strongly influenced by the size of the basis set nor by the method of electron correlation employed. Energetics for low-lying excited states of BLi and BLi₂ were determined. The dissociaton energies obtained with B3LYP/6-31G(d) theory are in excellent agreement with those obtained with the highest levels of theory.