InC_n~+(n=1-10)团簇的密度泛函理论研究

利用密度泛函理论的B3LYP方法,在LANL2DZ水平上对碳基混合团簇InC_n~+(n=1—10)进行了系统研究,得到了这个团簇体系的最稳定几何构型以及基态结构的电子态、最低振动频率、总能量、自旋污染期望值、偶极距、转动常数等.计算结果显示:团簇的最稳定结构是In原子位于碳链末端的直线型构型;n为偶数的基态是三重态,除InC~+外,n为奇数的基态是单态.通过对增量结合能和能量二阶差分的计算和分析可以得出,随着团簇尺寸的增加,团簇的稳定性表现出强烈的奇强偶弱振荡规律.电离能的计算结果进一步证实了这种振荡规律的正确性.对系列团簇基态的磁性研究表明,团簇的磁矩随团簇尺寸的增加呈现出明显的奇弱偶强振荡规律.极化率的计算结果显示,极化率张量的平均值及各向异性不变量都随着团簇尺寸的增大而增大.

Density functional theory of InCn+(n=1–10) clusters

Small indium-doped carbon clusters InC_n⁺(n=1–10) are systematically studied by the density functional theory at the B3 LYP/LANL2 DZ level. The computed properties include equilibrium geometries, electronic energies, vibrational frequencies, dipole moments and rotational constants for individual species. The calculation results show that the open-chain linear isomers with the indium atom bound to the end of the carbon chain are the most stable geometry in all cases. There must exist a cyclic or fan structure in the metastable or the third stable structure of cluster. The bigger the size of the cluster, the more obvious the stability of the structure is. The electronic ground state is found to be alternately a triplet for even n and a singlet for odd n with the only exception of InC⁺. It is generally observed that the spin contamination is not serious for all electronic ground states because the 2> values are uniform and in general deviate slightly from the pure spin values, and the B3 LYP wave functions are nearly spin-pure. It is also found that in the lowest-energy linear structure, the In–C bond is longer (from 2.319 Å to 2.850 Å) than the corresponding C–C bonds in a range from 1.268 Å to 1.360 Å. The C–C distances can be assimilated to moderately strong double bonds underlying a clear π bonding in the corresponding structures. In addition, we observe a clear alternation in C–C distances. The C_odd–C_even distances are shorter than the C_even–C_odd ones which mainly results from the charge distribution and spin density. According to the calculation and analysis of the incremental binding energy and the second difference we can deduce an even-odd alternation in the cluster stability for the linear InC_n⁺, with their n-odd members being more stable than the adjacent even-numbered ones. This parity effect also appears in the adiabatic ionization potential curves. The analysis of magnetic properties shows the even-odd alternation with n-even clusters presenting higher values of magnetic moment than n-odd ones. The study of the polarizability indicates that the average values of both the polarization tensors and the anisotropic invariants increase with the size of cluster increasing.