Au₂Si₂₀: a honeycomb-shaped structure with short Au−Au single bond at the centre coordinated by twelve Si₅ pentagons and reinforced by strong Au−Si interactions and aromaticity

Investigating the structures and properties of large-sized silicon clusters doped with multiple Au atoms can provide valuable microscopic information for gold-catalyzed high-quality Si nanowire and Au−Si alloying reactions, and also for the production of cluster-assembled functional materials. In this work, a quantum chemical investigation on the structural and electronic properties of double Au atoms doped Si₂₀ cluster using density functional theory calculations was performed. The lowest-lying isomers of $A{u}_2{Si}_{20}^{-/0/+}$ (The meaning of the acronym: $A{u}_2{Si}_{20}^{-/0/+}$ refers to Au₂Si₂₀ cluster with a negative charge, neutral state, and a positive charge, respectively.) were found to all adopt a C_2h symmetric Au₂-endohedral honeycomb-shaped structure consisting of twelve Si₅ pentagons. Interestingly, in the anionic, neutral, and cationic Au₂Si₂₀, twelve Si₅ pentagons can be stabilised by two Au atoms. The two Au atoms in $A{u}_2{Si}_{20}^{-/0/+}$ tend to occupy high coordinate sites and exhibit strong aurophilic interactions. In addition, the Au−Si bonds show both covalent and ionic bonding characters. Moreover, $A{u}_2{Si}_{20}^{-}$, Au₂Si₂₀, and $A{u}_2{Si}_{20}^{+}$ are all aromatic.