Assembling Au₄ Tetrahedra to 2D and 3D Superatomic Crystals Based on Superatomic-Network Model

Thiolate-protected gold nanoclusters (denoted as Aum(SR)n or AunLm) have received extensive attention both experimentally and theoretically. Understanding the growth mode of the Au4 unit in Aum(SR)n is of great significance for experimental synthesis and the search for new gold clusters. In this work, we first build six clusters of Au7(AuCl2)3, Au12(AuCl2)4, Au16(AuCl2)6, Au22(AuCl2)6, and Au30(AuCl2)6 with the Au4 unit as the basic building blocks. Density functional theory (DFT) calculations show that these newly designed clusters have high structural and electronic stabilities. Based on chemical bonding analysis, the electronic structures of these clusters follow the superatom network (SAN) model. Inspired by the cluster structures, we further predicted an Au4 two-dimensional (2D) monolayer and a three-dimensional (3D) crystal using graphene and diamond as templates, respectively. The computational results demonstrate that the two structures have high dynamic, thermal, and mechanical stabilities, and both structures exhibit metallic properties according to the band structures calculated at the HSE06 level. The chemical bonding analysis by the solid-state natural density partitioning (SSAdNDP) method indicates that they are superatomic crystals assembled by two electron Au4– superatoms. With this construction strategy, the new bonding pattern and properties of AunLm are studied and the structure types of gold are enriched