M@B12N12 (M=La-Lu)团簇结构性质与红外光谱的理论研究

Theoretical Study on Structural Properties and Infrared Spectra of M@B₁₂N₁₂ (M=La-Lu) Clusters

  • 摘要: 采用密度泛函理论对M@B12N12 (M=La-Lu) 团簇的几何结构、电子性质,电偶极性和红外吸收光谱进行详细研究。结果显示:B12N12团簇内嵌镧系原子后,结构稳定性增强,摩尔体积随原子序数的增加呈现逐渐减小趋势。自旋多重度方面,内嵌Sm、Er和Yb原子后为自旋单态;掺杂Pr、Pm、Ho、Tm和Lu时是二重态; 掺杂Ce,Gd,Dy时为三重态;内嵌La、Eu和Tb时为四重态; Nd掺杂时是五重态。HUMO-LUMO能隙变小,化学活性提升,且HOMO轨道倾向于分布在M原子与N原子附近,而LUMO轨道则多数仍分布在B原子周围。掺杂后,团簇的电偶极矩出现先增大后减小的变化,部分结构的电偶极矩接近零。极化率表现出振荡特征,其中B12N12Tm团簇的值最大。随着原子序数的增加,红外光谱吸收峰数量增多,其中,M@B12N12 (M=Nd,Sm,Er)团簇红外吸收峰发生蓝移,其余则表现为红移。

     

    Abstract: The geometric structures, electronic properties, electric dipole characteristics, and infrared absorption spectra of M@B₁₂N₁₂ (M=La-Lu) clusters were invested detailed by Density functional theory. The results show that after embedding lanthanide atoms into B₁₂N₁₂ clusters, the structural stability is enhanced, and the molar volume exhibits a gradually decreasing trend with the increase of atomic number. In terms of spin multiplicity, it is a singlet state after embedding Sm, Er and Yb atoms; a doublet state when doped with Pr, Pm, Ho, Tm and Lu; a triplet state when doped with Ce, Gd and Dy; a quartet state when embedding La, Eu and Tb; and a quintet state when doped with Nd. The HOMO-LUMO energy gap decreases, and the chemical activity is improved. The HOMO orbitals tend to be distributed near M atoms and N atoms, while most of the LUMO orbitals are still distributed around B atoms. After doping, the electric dipole moment of the clusters shows a variation trend of first increasing and then decreasing, and the electric dipole moment of some structures is close to zero. The polarizability exhibits oscillating characteristics, among which the value of B₁₂N₁₂Tm cluster is the largest. With the increase of atomic number, the number of absorption peaks in the infrared spectrum increases. Among them, the infrared absorption peaks of M@B₁₂N₁₂ (M=Nd, Sm, Er) clusters undergo a blue shift, while the rest show a red shift.

     

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