碱金属掺杂B_(18)^(0/-)团簇结构和特性研究

Study on structures and properties of alkali metals doped B_(18)^(0/-) clusters

硼基纳米材料因其独特分子结构和化学键成为团簇科学研究的重点。基于卡利普索结构预测程序和密度泛函理论,在PBE0/6-311+G(d)水平下系统分析了碱金属M_(2)(M=Li,Na,K)原子掺杂B_(18)^(0/-)团簇的结构和特性。结构搜索发现,所有全局极小结构均呈现管状结构。除Li_(2)B_(18)(C1点群对称)外,其他高对称结构(D9d点群对称)中2个掺杂碱金属原子均位居管两侧的对称轴线上。基于全局极小结构的稳定性分析表明,K_(2)B_(18)和Li_(2)B_(18)^(-)团簇在各自体系中拥有相对高的稳定性。电荷研究发现,掺杂体系中电荷从碱金属M原子向硼原子转移。磁性分析表明,闭壳层电子结构体系(Li_(2)B_(18)、Na_(2)B_(18)和K_(2)B_(18))总磁矩为0,开壳层电子结构体系(Li_(2)B_(18)^(-)、Na_(2)B_(18)^(-)和K_(2)B_(18)^(-))分别拥有1μB的总磁矩。分析偶极矩和极化率发现,高对称性结构对应的偶极矩和第一超极化率为0。此外,基于Multiwfn软件,拟合出了体系的光电子能谱、红外谱和拉曼谱。最后,讨论了体系的温度和热力学参数(定容热容Cv和标准熵S)之间的关系。

Boron-based nanomaterials have attracted significant attention in cluster science due to their unique molecular structures and chemical bonding.In this study,we systematically investigated the structures and properties of M_(2)(M=Li,Na,K)doped B_(18)^(0/-) clusters at the PBE0/6-311+G(d)level using the CALYPSO structure prediction program combined with density functional theory.Structure predictions found that all doped systems exhibit tubular configurations.Except for Li_(2)B_(18),which has C1 point group symmetry,the global minimum structures of the other clusters adopt a D9d point group symmetry tubular shape,with the two M atoms localized along the axis of the tubular structure.Stability analyses indicated that K_(2)B_(18) and Li_(2)B_(18)^(-) clusters exhibit relatively strong stability in the neutral and anionic series,respectively.Charge transfer analysis revealed that electrons are transferred from the M atoms to the base boron fragment.Magnetic properties analysis indicated that the total magnetic moment is zero for the closed-shell structures of Li_(2)B_(18),Na_(2)B_(18) and K_(2)B_(18) clusters.However,the open shell structures of Li_(2)B_(18)^(-),Na_(2)B_(18)^(-) and K_(2)B_(18)^(-) clusters exhibit magnetic moments of 1μB.Dipole moment and polarizability analyses showed that both the dipole moment and the first hyperpolarizability are zero for the highly symmetrical structures.Additionally,simulated photoelectron spectra,IR spectra and Raman spectra,generated using Multiwfn software,provide a theoretical basis for further experiments.At last,the relationships between thermodynamic parameters(Cv and S)and temperature were discussed.