Electronic structure and thermochemical properties of neutral and anionic rhodium clusters Rhn, n = 2–13. Evolution of structures and stabilities of binary clusters RhmM (M = Fe, Co, Ni; m = 1–6)

Abstract

Geometric and electronic structures, and relative stabilities of rhodium clusters Rhn, n=2–13 and binary clusters RhmM with M=Fe, Co, Ni and m=1–6 are investigated using DFT calculations with the BP86 functional and LANL2DZ basis set. The growth mechanism can be formulated as follows: (i) the small pure clusters Rhn with n⩽7 are generated by directly doping one Rh atom into the smaller clusters Rhn−1, (ii) in the cases n⩾8, the ground state structures of these clusters tend to grow from a cube except for Rh9 cluster. Meanwhile, binary clusters RhmM can be formed by either substituting one Rh in the global minima of corresponding Rhm+1 clusters by an M atom or by doping one Rh into the corresponding smaller size Rhm−1M. The latter is more favored, apart from Rh2Fe and Rh3Fe. Electron affinities, ionization energies are computed for pure Rhn clusters. Comparison with experiments shows that the chosen functional is reliable in predicting EA and IE values. Binding energy per atom (Eb), second-order difference and the stepwise dissociation energies are evaluated for both pure and bimetallic clusters. The addition of M dopant considerably increases the Eb values of the impure RhmM clusters as compared to those of corresponding pure hosts.