Effect of Ligands on the Geometric and Electronic Structure of Au13 Clusters

We have carried out scalar relativistic density functional theory calculations within the projector augmented wave scheme and the pseudopotential approach, to examine the effect of ligands on the geometric and electronic structure of four Au-13 isomers: planar. flake, cuboctahedral, and icosahedral clusters. We find, in agreement with previous theoretical calculations, that for the clean cluster the planar geometry has the lowest total energy while the icosahedral and cuboctahedral structures undergo Jahn-Teller distortion. On the other hand, when ligated by phosphines, the icosahedron is found to assume the lowest total energy. The rationale for the stabilization of the icosahedron in the ligated Au-13 cluster is traced to the ligand-induced charge transfer from the surface Au-Au to All-ligand bonds leading to the formation of a strong Au-ligand covalent bond and introduction of a compressive strain which further weakens the Au-Au bonds.