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。本文中,采用卡利普索结构预测程序结合密度泛函理论,在PBE0/6-311+G(d)水平下系统研究了碱金属M2(M=Li, Na, K)原子对B180/^?团簇的结构的调控。结构搜索发现,所有全局极小结构均呈现管状结构。除Li2B18外(C1),其它高对称结构中(D9d)两个掺杂的碱金属原子位居管两侧的对称轴线上。紧接着,基于全局极小结构,稳定性分析表明K2B18和Li2B18?^{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(Li2B18、Na2B18和K2B18)的磁矩为零,开壳层电子结构体系(Li2B18?^、Na2B18?^和K2B18?⁾分别具有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零,K2B180/?^{团簇拥有最大的平均极化率和各向异性极化率},对外场的响应最强。此外,拟合出了光电子能谱、红外谱、拉曼谱等光谱。最后,讨论了温度和热力学参数之间的函数关系。

Boron-based nanomaterials have become the focus of cluster scientific research because of their unique molecular structure and chemical bonds. Here, we systematically studied the regulation of M2 (M=Li, Na, K) on the structure of B180/^? clusters at the PBE0/6-311+G(d) level by using the CALYPSO structure prediction program combined with density functional theory. Structure prediction found that all doped systems exhibit tubular structures. Moreover, except for the Li2B18 with C1 point symmetry, the global minimum structures of the other clusters favor D9d point symmetry tubular shape, where the two M atoms are localized on the axis of the tubular structure. Subsequently, based on the global minimum structures, the stability studies indicated that K2B18 and Li2B18?cluster have relatively strong stability in neutral and anionic series, respectively. Charge transfer analyses revealed the charge transfer occurs from the M atoms to the base boron fragment. Magnetic properties analyses indicated that the total magnetic moment is zero for the closed-shell structures of Li2B18, Na2B18 and K2B18 clusters; however, the open-shell structures of Li2B18?, Na2B18? and K2B18? clusters have the magnetic moments with the values of 1μB. Upon dipole moment and polarizability analysis, the dipole moment and the magnitude of first hyperpolarizability are zero for the highly symmetrical structure, respectively. Moreover, K2B180/? clusters with highest mean dipole polarizability show a stronger anisotropic response to the exteranl field. Additionally, the simulated photoelectron spectra, IR spectra and Raman spectra were also presented, which could provide a theoretical basis for further experiments. At last, the relationships between Cv (S) and T were discussed.

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国家自然科学基金资助项目(11904328,12104416)；河南省高等学校重点科研项目计划(21A460023)；郑州师范学院本科教学改革研究项目(JXGG-20773)资助。