Theoretical studies of B₂Li_n (n = 1-4)

Structures and energies of the binary B₂Li_n (n = 1-4) clusters are predicted with the HF, MP2, and B3LYP methods using the 6-31G(d) basis set, including energy evaluations at G2MP2 and CBS-Q and the larger 6-311+G(2d) basis set for B3LYP. All systems except B₂Li₄ are also computed with the CASSCF method because of spin contamination for several of the open-shell systems. These were followed by energy evaluations with multiconfigurational perturbation theory. The global B₂Li minimum has a C_2v triangular form of which the ²B₁ state is 13 kcal/mol more stable than the ²A₁ state. A bent double Li-bridged structure (C_2v) is the global B₂Li₂ minimum with a 2.0 kcal/mol inversion barrier. The global minimum for B₂Li₃ is a triple Li-bridged propellane-like structure (Dy, ), and for B₂LJ₄ it is the quadruple Li-bridged structure (D_eh, ). All these structure have a high degree of ionicity, but in B₂Li_n stabilization through LiLi interactions also become important. Structural patterns for the isomers of these clusters are examined. Cohesive energies (B₂Li_n → B₂ + Li_n) and Li and Li₂ elimination energies are analyzed in terms of cluster stabilities.