We propose a new variational method, based on the ab initio Hartree-Fock methods, for the purpose of calculating efficiently both the equilibrium geometry and the stability of alkali-metal microclusters. Applying this method to lithium clusters, up to ${\mathrm{Li}}_{36}$, we are able to find a close correlation between the observed magic numbers and the calculated stable cluster size. Furthermore, we find that lithium clusters larger than ${\mathrm{Li}}_{26}$ have an ordered structure, while clusters smaller than this do not. This is suggestive of the evolution of the clusters to the bulk structure of solid lithium.

• Received 18 January 1990

DOI:https://doi.org/10.1103/PhysRevLett.65.2696