Theoretical Research On Constructing New Superatomic Clusters With Multiple External Fields

As an important component of atomic clusters,superatoms have attracted considerable attention because they can mimic the chemistry of an atom in the periodic table.The emergence of superatoms provides a richer structural unit for new multifunctional nanomaterials and devices.As two important branches of superatoms,superalkalis and superhalogens have broad application prospects in nonlinear optical materials,charge-transfer salts,multifunctional materials,redox-reaction and so on,and has become a research hotspot in recent years.Conventional electronic rules,which involve the Jellium rule,18-electron rule,Wade-Mingos rule,isovalent rule,and so on,have been successfully employed to construct superatoms.Based on density functional theory(DFT)calculations,this paper uses transition metal clusters as a model,introduces the ligand field or the ordered external electric field(OEEF)into the cluster field,and proposes an effective strategy for using multiple fields to construct superatoms.The influence of the external field on the cluster geometry,electronic properties and catalytic reaction is analyzed.The main contents of this dissertation are summarized as follows:(1)The effect of the ligand field on the electronic properties of Au19 clusters is studied:Au19 and triethylphosphine ligand(PEt3)can be combined to form a charge transfer complex.As the number of ligands increases,the ionization energy of the clusters continues to decrease,and the clusters change from a non-superalkalis to a superalkalis.Interestingly,although the electronic properties of the clusters changed significantly,the HOMO-LUMO gap barely changed.In addition,we also found that the ligands affect the electronic properties of the clusters mainly by affecting the electronic spectra of the clusters.Moreover,the upward shift of the HOMO position of the Au19 was proved to be the cause of the decrease of AIE.This work not only provides a new perspective for exploring the electronic properties of ligand-protected gold nanoclusters,but also enriches the research strategies for the construction of superalkalis.(2)The effect of the OEEF on the geometrical structures,electronic properties,and catalytic reaction of Au19 was systematically investigated using DFT calculations.Although the OEEF with a certain intensity has little effect on the geometric stability of Au19,it does significantly change its electronic properties.With the enhancement of OEEF,the EA value of Au19 gradually increases,and there is a good polynomial fitting relationship with the OEEF intensity,so as to achieve precise and continuous control of the electronic properties of transition metal clusters.On this basis,the OEEF was manifested to have the power to enable the Au20 cluster to achieve the transition from non-superhalogen to superhalogen.In addition,we also calculated the influence mechanism of OEEF on CO oxidation on Au19 clusters.The theoretical results show that the adsorption of gas molecules and the energy barrier of CO oxidation reaction are obviously decreased after the introduction of OEEF with different intensities.Considering the convenient source and ease control of the OEEF,the findings highlighted here may boost the potential applications in low-temperature CO oxidation and even other types of reactions.(3)The effects of the OEEF on the geometrical structures and electronic properties of transition metal clusters Ag19 and Cu19 have been theoretically investigated based on density functional theory calculations.Similarly,although OEEF does not affect the geometric configuration and energy stability of Ag19 and Cu19,it has a significant impact on their electronic properties,especially EA.Specifically,when F+z is 0.024 au,the EA value of Ag19 is increased to 3.88eV,which is larger than that of all halogens in the periodic table,showing significant superhalogen characteristics.More interestingly,the EA value of Ag19 can be expressed as a function of OEEF intensity,showing that OEEF has a great advantage in adjusting cluster EAs compared to traditional methods,namely the precise and continuous modulation.In addition,our study also found that the OEEF can continuously stabilize the LUMO levels of Ag19 and Cu19 and the directional sensitivity to the charge transfer process on the Ag19 surface.These results further validate the ability of external electric field to regulate the electronic properties of atomic clusters,and provide a basis for designing superatoms or superatom assembly nanomaterials.