Second-order superatoms: Au 52 -PAP featuring a three-dimensional cluster-of-clusters core.

The recent characterization of Au 52 -PAP cluster can be viewed as a three-dimensional arrangement featuring four Au 13 motifs. As a result, a new set of superatomic orbitals are built up from the superatomic shell of each constituent unit, denoted by 1S' 2 1P' 6 2S' 2 1D' 10 2P' 6 1F' 6 and, thus, referred to as a second-order superatomic shell structure. This favors the rationalization of larger species toward the formation of cluster-assembled materials of different sizes.