摘要
用DVM-X.方法计算了中性Co_6Te_8团簇的分子轨道.对于具有O_h点群对称性的结构,分子轨道的结果表明该团簇的基态是顺磁性的,与实验结果不相容;如果考虑到Jahn-Teller效应,用D_(4h)点群对称性的计算结果得出了逆磁性的基态分子轨道,并且在HOMO以上的第一个未占据能级(LUMO)与HO-MO之间的能隙将近0.018eV左右.作者认为:从全满的HOMO向LUMO轨道迁移一个电子的顺磁低激发态对Co_6Te_8团簇的高温顺磁性有显著的贡献,有限温度下的热统计平均是这两个状态之间的混合态.分子轨道的计算结果与实验结果和混合价模型的图象是相容的.
The anomalous megnetic property of neutral Co6Te8 cluster is investigated by DVM-Xa calculation of molecular orbitals. For the structure with Oh symmetry, the DVM-Xa results shows that the electronic configuration of ground state is non magnetic, and is disagreement with experimental data. However,if the John-Teller effect due to non spherical charge distribution of partially filled 3d levels of transition metal is involved, i. e. , the D4h symmentry is adopted for Co6Te8 cluster the mixed-valence-like electronic configuration is obtained. The ground state with John-Teller distortion is non magnetic with double-occupied HOMO,and the LUMO is low-lying and the gap between HOMO and LUMO is about 0. 018eV. These results explain qualitatively the experimental data well and are in good agreement with mixed-valence model of heavy fermion system.
