Theoretical study of the electronic states of Zr5

Geometries and energy separations of low-lying electronic states of Zr5 with difference structures have been investigated by complete active space multi-configuration self-consistent field method followed by large-scale multi-reference singles + doubles configuration interaction computations that included up to 3 million configurations. Three nearly degenerate electronic states, namely 3A2 (C2v) with a distorted tetragonal pyramid structure and 1A′ and 5A′ (Cs) with distorted edge capped tetrahedral geometries were found as the candidates for the ground state of Zr5. The atomization and dissociation energies have been calculated and compared with smaller clusters.