ABINITIO MRD-CI STUDY OF NEUTRAL AND CHARGED GA-2, GA-3 AND GA-4 CLUSTERS AND COMPARISON WITH CORRESPONDING BORON AND ALUMINUM CLUSTERS

MRD-CI calculations were performed on Ga, Ga2, Ga3, Ga4 and on the corresponding positive and negative ions. In general, pseudopotentials were used, and 4 s4 p/2 s2 p basis sets with s and p diffuse functions and one or two d functions. For Ga2, all-electron calculations were also performed. For Ga2(±), potential functions for ground and low-lying excited states are given. For Ga3(±), geometries were optimized both in C2 v and D∞h symmetry. The lowest state of Ga3+ is found to be1Σg+, of Ga34A2, and of Ga3-1A1 (D3 h). Ionization potentials and electron affinities of Ga3 were evaluated. Many low-lying excited states of Ga3(±) were found. Rhombic (D2 h, including square D4 h), tetrahedral (Td), T-shaped (C2 v) and linear structures (D∞h) were investigated in the search for the lowest state of Ga4. A square-planar arrangement of the nuclei, with Re = 5.30 a0, was found to have the lowest energy. The other geometries lie about 0.5 eV higher. In D2 h symmetry, low-lying excited states of Ga4, as well as ground and excited states of Ga4+ and Ga4- were studied. Geometries, ionization potentials, electron affinities, atomization and fragmentation energies of Gan are compared with corresponding data for Bn and Aln. Typical changes in going from first-row to third-row atoms are observed. © 1990 Springer-Verlag.