+: A Superatomic Molecule with a Au13 FCC Core

ABSTRACT: A unique tetrahedral structure of Au17 + (Td) is found by using first-principles global optimization, which lies 0.40 eV lower in energy than the previously known structure and has a fairly large HOMO−LUMO gap (1.46 eV) at the TPSS/def2-TZVP level. For neutral Au17, this tetrahedral structure is distorted to D2d symmetry but is also 0.18 eV lower in energy than the previous flat cage structure. Au17 + (Td) has a FCC Au13 octahedral core, and the other four gold atoms are above its four triangular faces. Magic electronic stability of the cluster is explained by the super valence bond model, of which it can be seen as a superatomic molecule in the electronic structure. Moreover, the cluster can also be viewed as a network of eight 2e-superatoms. This Au17 cluster mimics the behavior of the Au20 pyramid, known as a unique one among the family of gold clusters since its discovery in 2003, in electronic structures. 1