Electronic and geometric structure of LI4 and Na4 clusters

Abstract
The properties of the Li4 and Na 4 clusters are determined utilizing ab initio CI methods. The rhombic and bent square geometries of these alkalai metal clusters are predicted to be the most stable arrangements for the singlet and triplet states respectively. More symmetrical planar square and tetrahedron Li4 and Na4 clusters exhibit pronounced biradical features and are therefore highly unstable. The conjecture is made that the biradical character of some cluster arrangements might be connected with the catalytic activity of geometric irregularities in the surface of catalysator.