Chemical Bonding and Electronic Structure of Small Homonuclear Clusters of Elements of Groups IA, IIA, IIIA and IVA

The clusters Lik(k = 3–8), Na4, K4, Bex(x = 3–13), Mgy, Cay, Aly(y = 3–5) and Gez(z = 3–6) are investigated employing the ab initio CI method. — The bond in alkali metal clusters is due to the interaction of the outer s orbitals but p polarization functions are essential for a correct prediction of the electronic structure and stability of possible geometries of these clusters. In alkaline earth metal clusters the role of sp hybridization is crucial for the appearance of attractive interactions. The most relevant factor determining the stability of Al and Ge clusters is the bonding between p atomic orbitals. The spin properties of small clusters, which are important for their stability, are determined by their geometry and symmetry. — The most stable clusters of elements which crystallize in compact structures (bcc, fcc and hcp) are always sections of the corresponding crystal lattices. On the contrary, the Ge clusters exhibiting large stability are not parts of the diamond lattice and can be considered as deformed parts of more compact lattices. — The binding energy per atom of Li and Be clusters qualitatively converges to the cohesive energy of the metals with the growth of the cluster size. — In the largest clusters the existence of very small singlet‐triplet energy splittings indicates the development of a metallic character.