Studies On Electronic Structure Of （Au₂S）_n Clusters By Density Functional Theory

In recent years, clusters have attracted great interest due to its unique chemical and physical properties. Although a mass of investigations on metal clusters such as alkali metal compounds and gold clusters have been performed, there are still many problems to be solved. The rapid developments of computational methods and technology lay the foundation for the studies of the geometry and electronic structures of clusters. The density functional theory has become an important method in theoretical chemical own its low computation and high precision characteristics currently.In this paper, the structure of Zn8L8 clusters (L= H, CN, CH3) is predicted according to the superatomic principle and investigated using density function theory (DFT). Secondly, we explore the structural evolution of (Au2S)n (n= 1-8) clusters using the genetic algorithm (GA) combining with density function theory and analyze the stability of geometry and electronic structure of the cluster.The main studies are as follows:1. Theoretical study of superatomic-molecule Zn8L8 (L= H, CN, CH3) clustersThe structure of ZnsLs clusters (L= H, CN, CH3) is predicted according to the superatomic principle and investigated using density function theory. It is found that the Zn8L8 is a stable complex with large HOMO-LUMO gap and binding energy. The electron distribution in the nanoparticle has been discovered and further insight into the bonding on the metal surface has been provided through the adaptive natural density partitioning (AdNDP) analysis. Even more, Zn8(CN)8 has a larger HOMO-LUMO gap, binding energy and aromatic according to the NICS criterion, which all indicate Zn8(CN)8 has got a stable structure.2. Structural evolution of (Au2S)n (n= 1-8) clusters from first principles global optimizationWe explore the structural evolution of (Au2S)n (n= 1-8) clusters using a first principles global minimization technique, namely, genetic algorithm from density functional theory geometry optimization (GA-DFT). The growth sequence and pattern for n from 1 to 8 are analysed from the perspective of geometric shell formation. The global minimum structures are planar at n= 1-3, three-dimensional at n= 4-8. The formation of these structures are attributed to the high stability of S-Au-S structural unit and particularly the AU3S3 and Au4S4 rings. Chemical bonding analysis reveals that the three-dimensional clusters (n= 4-8) can be viewed as [Au2n-xSn]x-·xAu+ according to the electronic structures. The Au+ cations are not involved in any S-Au covalent bond, however, are attracted by only Au…Au aurophilic interactions. Direct evidence for the Au…Au aurophilicity are given by a noncovalent interaction index analysis. Such Au…Au aurophilic interactions play an important role in the stability of (Au2S)n clusters.