碘掺杂和非掺杂高取向反式聚乙炔导电性能的各向异性

Anisotropy of Conductivity for High Oriented Undoped and Iodine-doped trans-Polyacetylenes

本文应用量子化学EHMO/CO方法计算了高取向反式聚乙炔及其碘掺杂物的二维能带结构,并以此为依据讨论了它们导电性能的各向异性.平行于分子链方向的电导率与垂直于该方向的电导率之比(σ_■,/σ_⊥)取决于这两个方向上价带宽和导带宽的大小.碘掺杂后σ_■/σ_⊥下降,其原因是链间耦合增强的结果.这也使掺杂后的反式聚乙炔成为链间相互作用微弱的三维体系.计算结果与实验结果较好地吻合.

The two-dimensional band structures of high oriented undoped and iodine-doped trans-polyacetylenes are calculated by using the semiempirical EHMO/CO quantum chemical method, and the electronic ansotropies of them are discussed. The results show that the ratio between the conductivity in the direction parallel to the molecular chain and the conductivity in the direction perpendicular to the molecular chain (σ_〃/σ_1) depends upon the valence band widthes and the conduction band widthes in the two directions. The σ_〃/σ_1 is decreased by the iodine-doping due to the increased interchain coupling. The results are in good agreement with the experimental observations.