Theoretical study of the electronic states of Rhn+ (n=3–5)

Abstract

Geometries and energy separations of the various low-lying electronic states of Rh3+, Rh4+, and Rh5+ clusters with different structural arrangements have been investigated. The complete active space multiconfiguration self-consistent field method, (CASMCSCF) followed by large scale multireference singles plus doubles configuration interaction (MRSDCI) computations that included up to 1.6 million configurations for Rh3+, 1.5 million configurations for Rh4+, and 2.7 million configurations for Rh5+, were used. Four nearly degenerate electronic states were found for Rh3+. The A′6 electronic state of the pyramidal structure of Rh4+ was found to be the ground state. Although the A″6 electronic state of Rh4+ with the same geometry was found to be close in energy at the CASMCSCF level, it is 0.5 eV higher at the higher level of theory. Two nearly degenerate electronic states (A″5 and A″5) of the distorted edge capped tetrahedron structure of Rh5+ were found as candidates for the ground state of this cluster. Mulliken population analysis has been carried out on these cationic clusters to investigate their bonding properties.