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本文采用以EHMO为基础的紧束缚近似方法计算了同分异构复合物1-N-Mci TCNQ_2和2-N-Mci TCNQ_2的能带结构。通过计算谐振稳定能估算复合物中TCNQ的电荷。计算结果表明,复合物晶体中的给体N-Mci对一维能带的前沿轨道无影响。1-N-Mci和2-N-Mci的几何形状不同,在晶体堆积能量上影响TCNQ的排列,使两个复合物的TCNQ堆积方式不同,能带结构也就不一样了。1-N-Mci TCNQ_2复合物的TCNQ之间π-π轨道迭合较好,能隙小。LU带色散大,LU轨道上的电子为末充满状态(δ≈1.77),具有较好的导电性能。2-N-Mci TCNQ_2复合物中TCNQ二聚体之间π-π轨道重叠不好,能隙大,LU带宽很窄,LU轨道上电子为半充满状态(δ≈1.0),易于形成磁绝缘体,其导电性比1-N-Mci TCNQ_2差,这与实验结果是一致的。
In this paper, the band structure of 1-N-Mci TCNQ_2 and 2-N-Mci TCNQ_2 are calculated using the tight bond approximation method based on EHMO. The charge of TCNQ in the complex can be estimated by calculating the resonance stability. The calculated results show that the donor N-Mci in the complex crystal has no effect on the frontier orbit of the one-dimensional band. The geometries of 1-N-Mci and 2-N-Mci are different, affecting the arrangement of TCNQ in the energy of crystal packing, making the TCNQ accumulation modes of the two composites different, and the band structure is also different. The π-π orbitals of the 1-N-Mci TCNQ_2 complexes are better and the energy gap is smaller. LU with large dispersion, LU orbitals for the end of the charge state (δ ≈ 1.77), has good electrical conductivity. The π-π orbit overlap between TCNQ dimers in 2-N-Mci TCNQ_2 complex is not good, the energy gap is large, the LU bandwidth is narrow, and the electron on the LU orbit is half full (δ≈1.0) , Its conductivity is worse than 1-N-Mci TCNQ_2, which is consistent with the experimental results.