"No-pair bonding" in high-spin lithium clusters: ⁿ⁺¹U_n (n = 2-6)

High-spin lithium clusters (ⁿ⁺¹Li_n, n = 2-6) have been studied using several density functional methods. Although these high-spin clusters have no bonding electron pairs, they are stable with respect to isolated lithium atoms. Full geometry optimizations have been performed with alternatives under a variety of symmetry constraints which led to local minima. In general, the most stable structure is the one with the maximum coordination number for the lithium atoms. The agreement between B3P86/cc-pVDZ and B3PW91/cc-pVDZ density functional methods with UQCISD(T)/6-31G* and UCCSD(T)/cc-pVDZ calculations is excellent. Trends of bond dissociation energies are discussed as a function of total number of "bonds" and number of atoms.