密度泛函理论研究CeSi_n(n = 1~8)的结构与性质

Study on the Structures and Properties of CeSi_n (n = 1 - 8) with Density Functional Theory

摘要: 采用B3LYP结合稀土元素小核ECP28MWB基组，研究了CeSi_n (n = 1~8)体系的几何构型，报导了其基态结构，分析了其基态的相对稳定性、磁性、电荷分布、偶极矩等性质。研究结果表明，CeSi_n基态可以看作是Ce取代Si_n+1上的一个Si原子所获得，除了CeSi基态是5重态之外，其它物质是3重态；在CeSi_n中，Ce原子是电子供体，Si_n团簇是电子受体，Ce原子的4f电子变化不大，主要失去6s电子，部分进入5d轨道，部分进入Si_n团簇；分裂能表明CeSi₂、CeSi₅和CeSi₈相对比较稳定，而CeSi₄和CeSi₇相对稳定性较差；CeSi的偶极矩最小，CeSi₈的偶极矩最大；CeSi_n团簇的磁矩主要由掺杂的Ce原子所提供。

Abstract: The geometries of CeSi_n (n = 1 - 8) were studied by means of the B3LYP method in combination with small core ECP28MWB basis sets of the rare earth metals. The ground state structures of CeSi_n (n = 1 - 8) clusters were reported. The properties of relative stabilities, magnetic moments, charge distributions and dipole moments were analyzed. The results revealed that the ground state structures of CeSi_n (n = 1 - 8) can be regarded as being derived from the lowest-energy structure of Si_n+1 by replacing a Si atom with a Ce atom. The ground state of all of these is triplet with the exception of CeSi, which is quintet. The Ce atom is electron donor and the Si_n cluster is electron acceptor. The 4f electrons of Ce atom have little changes. The main change is that the 6s electrons of Ce atom transfer to 5d orbitals and Si_n clusters. Dissociation energies showed that CeSi₂, CeSi₅ and CeSi₈ are more stable, and CeSi₄ and CeSi₇ are less stable. The dipole moments of CeSi are maximal and the dipole moments of CeSi₈ are minimal. The majority of total magnetic moments of CeSin are contributed by Ce atom.