Ab initiocalculations on small lithium clusters

We present a systematic study of the optimized geometries of several small closed-shell lithium clusters, as well as energy differences between isomers, using a variety of density functional and post-Hartree-Fock quantum chemical methods. Using different Gaussian basis sets we compare and contrast the results of the calculations for Li₂, Li₃⁺, Li₄, Li₅⁺, and Li₆ including two and three isomers of the latter two clusters, respectively. On the basis of these results a few guidelines for economically but nevertheless reliably studying lithium clusters are proposed.