Theoretical Research On Assembly Materials Of Gold Cluster Based On Superatom Network Model

In the field of clusters,some clusters of specific size can imitate the chemical behavior of a single or a series of atom in the periodic table of elements,we call such clusters as superatoms.Because of its particular nature,it has aroused a research boom among scholars in the academic field for more than ten years.By analyzing the characteristics of these clusters,the periodic table can be effectively extended to third dimension.By mastering the bonding characteristics of atoms,we can better promote the development of cluster field.As the basic construction unit of assembly material,the properties of the clusters can be theoretically incorporated into the designed materials.We explore its structure and function so as to realize the accurate and controllable properties and design the ideal material.In this paper,the superatom network model is used as the theoretical guidance to design two-dimensional and three-dimensional new materials,and the assembly process from clusters to solids is studied.To study the problem of bonding,we separately studied the structure and properties of materials.We hope our research can give new thought for prediction of new cluster assembly materials and give practical help for experiments.The research contents includes the following three aspects.1.Prediction of a two-dimensional gold based on superatom networks modelDesigning novel materials with fascinating chemical properties have attract more attention for new materials innovation.According to the structural characters of designed ligand-protected gold nanoclusters cluster,the fusing of Au₇units moieties reminds us of the roadmap of fusing benzene rings and then to two-dimensional（2D）infinite graphene.We used tetrahedral Au₄（2e）as an elementary block to replace the C atoms in graphene with the Au₇monomers.Each Au₇monomer by sharing the plane and vertices gold atoms to form a planar 2D monolayer gold.Our calculations demonstrated that the 2D Au monolayer has befitting cohesive energy,and the value of the phonon spectrum is greater than zero.The thermodynamically stability is proved by Molecular dynamics simulations.In addition,the analysis of energy band and density of states showed that 2D monolayer gold is a kind of metal,although the valence band is separated from the conduction band,they all cross the Fermi level.SSAd NDP bonding analysis showed that 2D monolayer gold can be regarded as the product of a superatom network（SAN）.According to the bonding properties of this material,it can provide new ideas for exploring more pure metal cluster assembly materials.2.Theoretical research of three-dimensional gold based on superatom networks modelWith superatom as basic building blocks,cluster assembly into new solid materials has always been a research hotspot in the area of assembly materials.How to select the appropriate elementary unit,so that the properties of the material can be ideal and controllable,also make the majority of researchers confused.So far,the tetrahedral Au₄（2e）as the basic building unit has been used for experimental synthesis and theoretical prediction of a series of ligand-protected gold nanoclusters.On the basis of the idea of a superatom network（SAN）model,we first constructed a ligand-protected gold nanocluster Au₁₆（Au Cl₂）,which is consists of tetrahedral Au₄units with four shared vertices.Bonding analysis shows that Au₁₆（Au Cl₂）cluster meet our expected idea.On the basis of the geometric structure characteristics of Au₁₆（Au Cl₂）cluster,we used face-centered cubic（fcc）diamond as a template to design a three-dimensional（3D）solid material of gold and formed by sharing atoms with tetrahedral Au₄units,which we donated as fcc-Au₄.At the same time,the kinetic and thermodynamic analysis of fcc-Au₄proves that it is stable in both kinetics and thermodynamics.Fcc-Au4energy band calculation prove that it is metal and has zero band gap.Although the valence band maximum（VBM）is completely separated from the conduction band minimum（CBM）,it passes through the Fermi level.SSAd NDP bonding analysis shows that fcc-Au₄can be regarded as an extension of the SAN.Our work focuses on extending the SAN model from clusters to solids,thus providing new horizons for exploring more cluster assembled materials.3.Stabilization of the[cyclo-N₅]^-anion by Lewis acid-base interactionsIt is an attractive problem to stabilize cyclopentazolate anion[cyclo-N₅]^-because of its excellent application in the area of energy density materials.Since there are lone pairs in the Pz direction on the N atoms,there is a repulsion between the adjacent lone pairs,which leads to[cyclo-N₅]^-instability without ligand protection,how to propose reasonable schemes to stabilize[cyclo-N₅]^-experimentally and theoretically has aroused widespread interest.Therefore,a series of ion salts containing[cyclo-N₅]^-were synthesized and studied.In this work,we expect if the[cyclo-N₅]^-can be stabilized by the coordination with acidic ligands,by weakening the multi repulsion from the lone pairs to stabilize the[cyclo-N₅]^-.The two compounds of[N₅（BH₃）₅]^-,and[N₅（Ag CN）₅]^-have been designed and compared on account of the Lewis acid-base theory.[N₅（H₂O）₅]^-is designed to evaluate the effect of hydrogen bond in the stabilization.For all the structures,we study the bonding properties and thermal stabilities based on the analysis of electronic properties and Car-Parrinello molecular dynamics（CPMD）simulations.The results indicate it is an effective method to stabilize[cyclo-N₅]^-by introducing the Lewis acid.Our insights on[cyclo-N₅]^-compounds with high thermal stability under ambient conditions will provide a new idea for the research new[cyclo-N₅]^-series compounds.