MB_(8)^(0/-)(M=Li、Na、Rb、Cs)团簇的几何结构和电子特性的研究

Study of the geometric structures and electronic properties of MB_(8)^(0/-)(M=Li,Na,Rb,Cs)clusters

本文结合CALYPSO软件和密度泛函理论,详细研究了MB_(8)^(0/-)(M=Li、Na、Rb、Cs)团簇的几何结构和成键特性.结构分析结果表明,MB_(8)^(0/-)团簇的基态结构都具有相似的几何构型,均为七棱锥状结构,并且随着掺杂原子的原子序数的增加,其M-B键的键长呈增加的趋势.通过稳定性分析,我们发现LiB_(8)^(-)团簇的最高占据分子轨道与最低未占据分子轨道之间的能隙(HOMO-LOMO能隙)以及结合能(E_(b))最大,因此这个团簇是体系中相对稳定的结构.电荷转移分析表明,掺杂的碱金属原子在所研究体系中充当着电子供体的角色.最后,成键分析的结果显示,LiB_(8)^(-)团簇的稳定性来源于B原子的2p轨道以及Li原子的2s和2p轨道在HOMO和LUMO的高贡献;适应性自然密度划分分析显示,B和Li原子都参与了成键,这同样有利于LiB_(8)^(-1)团簇的高稳定性的形成.希望我们的工作能为进一步研究碱金属掺杂硼团簇提供指导和帮助.

This work studied the geometric structures and bonding characteristics of MB_(8)^(0/-)(M=Li,Na,Rb,Cs)clusters by employing the CALYPSO software combined with DFT.The structural analysis results show that the ground state structures of MB_(8)^(0/-) clusters all have similar geometric configurations with the hexagonal pyramid structures,and the bond lengths of their M-B bonds tend to increase with the increase of the atomic number of doped atoms.Through stability analysis,we found that the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital(HOMO-LUMO energy gap)and average binding energy(E b)of LiB-8 cluster are the largest,so this cluster is a relatively stable structure in the system.Charge transfer analysis shows that the doped alkali metal atoms act as electron donors in the studied system.Finally,the results of bonding analysis show that the stability of LiB-18 cluster comes from the 2 p orbitals of B atoms and the high contributions of 2 s and 2 p orbitals of Li atoms at HOMO and LUMO;AdNDP analysis shows that both B and Li atoms are participated into the bonding,which is also conducive to the formation of high stability of LiB-8 clusters.We hope that our work can provide guidance for further research on alkali metal doped boron clusters.