Stability and other properties of Li13 clusters. An example of specific characteristics of clusters

Abstract
The icosahedron Li13 cluster has been found to be more stable than both the cubo-octahedron Li13 and a Li13 cluster section of the hcp packing employing the all electron MRD CI procedure. The ground states of these clusters are sextuplets with open shell electrons located entirely at the peripheral atoms. The contribution from the p orbitals to the one-electron density at the central atom is very large. The strength of the two-center bonds between central and peripheral atoms in icosahedron explains the larger stability of this cluster with respect to the fcc cubo-octahedron. The investigation of small Lin clusters shows that the most stable clusters for (n≤5) have planar geometries. It indicates the special stability of cluster geometries with fivefold rotational symmetry axis for Li6, Li7, and Li13 and gives further support to the conjecture that the clusters Li55 (Ih) are the seeds of the closed packed crystals of alkali metals.