Theoretical Studies Of Au Clusters By Density Functional Theory

As a new type of material,clusters have been studied extensively because of their unique physical and chemical properties,and gold nanoclusters has a wide application prospect on catalysis,magnetic materials and optical areas.However,the experimental reports about gold nanoclusters are less because of its complicated geometry structure and low synthesis rate.Thus,the theoretical calculation can play an important role in gold chemistry and provide theoretical foundation and basis for experiments.Moreover,density functional theory?DFT?has become one of the most important methods in theoretical chemistry because of its moderate computational consume and high precision.In this paper,the geometry structures of Au₂?AuL?_n clusters with n=1-12,L=Cl,SH,SCH₃,PH₂,and P?CH₃?₂,are investigated by using a method combining the genetic algorithm with DFT.The structures and size evolution of 2e superatom of them are investigated.We also seek to analyze the electronic structures and s²-d¹⁰ interaction in M@?AuSH?₆ clusters.The main studies are as follows:1.Size evolution of 2e superatom in Au₂?AuL?_1-12 clustersLigand-protected gold?Au-L?clusters have attracted much attention because of their unique properties.The concept of superatom model as a significant known to explain the electronic stability of Au-L clusters was suggested.In this field,there are many major progress but the size evolution of superatom is still little known due to limited experimental data.To give a direct and overall view of size evolution of superatom in Au-L clusters,we take the Au2-?AuL?1-12?L=Cl,SH,SCH₃,PH₂,P?CH₃?₂?system as a test case.The global minimum geometries are studied by using method combining the genetic algorithm with density functional theory.The gold cores in these structures consist of Au₃,Au₄,Au₅and Au₆ 2e-superatoms protected by staple motifs.The 2e-superatoms were confirmed by chemical bonding analysis using the adaptive natural density partitioning method.The aromatic properties of the center of these compounds have been explored by nucleus-independent chemical shifts method,which indicates that the superatoms are highly aromatic.This work gives a clear size-evolution of the 2e-superatomic Au-L clusters with one to twelve ligands,which discovers the growth mechanism of Au-L clusters with different ligands.2.Theoretical study of s²-d¹⁰ interaction in M@?AuSH?₆ clusterRecently,Zhu group experimentally produced a stable bimetallic compound Au₂Cu₆,the structure were successfully determined by X-ray crystallography which revealed that the benzenoid-type outer-loop hexagonal?CuSR?₆ framework is aggregated by two gold atom.The unusual structure feature attracted our attention,to give a direct and overall view of our idea about d¹⁰-s² closed-shell interaction,the M@?AuSH?₆?M = Mg,Zn,Cd,Hg,Cu-,Ag-,Au-?system is taken as a test case.The geometries of M@?AuSH?₆ clusters are optimized at tpssh/def2tzvp level.The chemical bonding are analysed by AdNDP?adaptive natural density partitioning?method which revealed that the existence of 7c-2e multicenter bond in M@?AuSH?₆ clusters.The valence electrons of M are 2?s²?and Au are d¹⁰,there is an usual d¹⁰-s² interaction between M and Au???,and we think the 7c-2e multicenter bond is the origin of d¹⁰-s² interaction in M@?AuSH?₆ cluster.Our work gave the support to the opinion of multicenter is the origin of d¹⁰-s² interaction through AdNDP,binding energy and LOL analysis in our calculation,which is a new breakthrough in metal cluster field.