Electron correlation effects in all-metal aromatic clusters: a quantum Monte Carlo study

Abstract

The electron correlation effects on the atomic and electronic structure of a few multiaromatic clusters XAl3– (X = Si, Ge, and Sn) are investigated using the diffusion quantum Monte Carlo method (DMC). We found that the vertical detachment energies are in very good agreement with available photoelectron spectroscopy data. The total binding energy of the clusters is dominated by the electron correlation energy contribution with about 55% of its total values. However, the binding energy gained in adding the dopant X into the Al3– unit to form the cluster XAl3– has been almost equally distributed among the contributions from Hartree–Fock (HF) and correlation energies. The resonance energy is found to be about 100 kcal/mol, which is roughly five times that of the organic aromatic compounds such as benzene. On the basis of some thermodynamical extremum principles we found that the order of decreasing stability of the clusters is SiAl3– ≈ GeAl3– > SnAl3–, the electron correlation impacting more the most stable clusters.