Theoretical Study of Aluminum-Sodium Bimetallic Clusters. I. Geometrical and Electronic Structures of AlnNa (n = 1–4)

Abstract

Abstract The geometrical and electronic structures of several small aluminum-sodium mixed clusters AlnNa and pure aluminum clusters Aln (n = 1–4) were examined with ab initio MO calculations. All the calculations were carried out at the restricted Hartree–Fock level of approximation for both closed and open shell systems. The structures of the most stable Aln cluster and neutral and cationic AlnNa clusters were fully optimized. The low and high spin multiplicities of each cluster were examined. The structure of the most stable state of the AlnNa clusters keeps the frame of the Al cluster unchanged, and the Al–Al distances become shorter than in the corresponding Al clusters. The calculated ionization energies by the ΔSCF method are qualitatively in agreement with the corresponding experimental values. The highest occupied molecular orbital of the neutral clusters suggests that an ionized electron is localized on the Al atoms, but the large orbital reorganization by ionization results in a substantial net positive charge on a sodium atom. The nature of chemical bond for the clusters is also examined.