| Clusters are a new type of material structure between atoms,molecules and macroscopic solid materials.The properties are also different from individual atoms and molecules,as well as from bulk materials.The properties of clusters are not derived from the simple linear extension or embedding of the properties of the two substances.In recent years,the research on boron clusters has always been a research hotspot,and the research on transition metal-doped binary boron clusters is also quite popular.The structures of transition metal-doped boron clusters studied theoretically include planar or pseudo-planar,half-sandwich,wheel-like,drum-like,reverse half-sandwich,and cage-like structures.The structure of a cluster determines its properties.To study its properties,it is necessary to study its structure first.In this article,we use CALYPSO cluster structure prediction,based on density functional theory,explore the geometric structure and stability of neutral and anionic transition metal niobium atom-doped boron clusters,and find that(1)The evolution of the structure of the neutral NbBn(n=10-20)clusters.In the neutral NbB(n=10-20)clusters,the structure gradually transitions from a half-sandwich structure to a drum-like structure.The stability analysis shows that the binding energy of almost all clusters is higher than 5.0 eV,and NbB13 clusters show obvious advantages in binding energy,second-order difference and HOMO-LUMO energy gap.This means that NbB13 cluster with Cs symmetry is the most stable among the neutral clusters,its binding energy value reaches 5.21eV,and the HOMO-LUMO energy gap value is as high as 2.84 eV.Therefore,we also performed chemical bond analysis on the NbB13 clusters.The results show that the 4d orbitals of niobium atoms and the 2p orbitals of boron atoms are also the main constituent orbitals of the molecular orbitals of NbB13 clusters.(2)The evolution of the structure of the anion NbBn-n=10-20)cluster is as follows:from the initial wheel-shaped structure to a half-sandwich structure,and then from a half-sandwich structure to a drum-shaped structure.The theoretical simulation of the photoelectron spectra of the anion NbBn-cluster is consistent with the experimental data,which proves the reliability of our results.Stability analysis shows that the binding energy of anionic clusters is higher than that of neutral clusters,and NbB12-clusters also stand out among the anionic cluster.The NbB12-cluster with C3vsymmetry has high binding energy,second-order difference value and HOMO-LUMO energy gap value of 3.10 eV,so it has high stability.Therefore,we conducted a chemical bond analysis on it and found that the 4d orbital of the niobium atom and the 2p orbital of the boron atom are relatively active,which together play a certain role in the stability of the NbB12-cluster.Both the neutral NbB13 cluster and the anionic NbB12-cluster are relatively stable,but the HOMO of the NbB12-cluster has a higher proportion of the charge of niobium atoms than the NbB13 cluster.Our research results show the geometric structure of niobium-doped boron-doped clusters and further enrich the geometric structure and chemical bond properties of boron-based clusters. |
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