Non-additive effects in small gold clusters

A post-Hartree–Fock second-order perturbational Møller–Plesset method was used to determine the many-body contributions in the interaction energy of Aun (n=3–6), clusters. Non-additive effects in these clusters were studied by decomposing the cluster binding energy in their n-body energy terms. It was found that the non-additive forces in small gold clusters are larger than the additive 2-body interactions and are the main factor to stabilize planar two-dimensional geometries as the lowest energy isomers. The effect of electron correlation in the interaction energy n-body decomposition was also analyzed and found to be important.