Molecular orbital calculation of octahedral (M6) clusters of Group VIII metals

Abstract

Iterative extended Hückel calculations have been performed for six atomic octahedral clusters of Group VIII metals (except Ir) at different internuclear distances, using different atomic functions for various values of the Wolfsberg–Helmholz parameter, F_k. The relative ordering and the structure of the calculated molecular orbitals have been found to be almost independent of the chosen parameters and the results have been compared with published data. The bond order, d-bandwidth and orbital occupancy suggest the generation of metallic properties to some extent in such tiny clusters. There is transfer of s electrons to both d- and p-orbitals for cluster bonding. The population of p-AOs decreases from Fe to Ni, Ru to Pd and Os to Pt in accordance with the increase in s–p promotional energy.