【作者】 张伟伟；

【导师】 赵仪；

【作者基本信息】 中国科学技术大学 ， 物理化学， 2010， 博士

【摘要】 本论文基于第一性原理和量子动力学研究了两种体系中的电子转移过程,一种是溶液中有机带电体系的分子内电子转移反应,另一种是有机半导体的电荷传输。对于溶液中的电子转移反应,以一种双肼自由基阳离子分子([22／hex／22]+)为例,理论研究了它在MeCN中的电子转移过程。首先,通过量子化学计算获得分子内电子转移的几个重要参数：重组能、电子耦合强度以及有效频率,同时也讨论了各种计算方法的有效性。然后利用这些参数结合扩展的Sumi-Marcus溶剂化反应扩散理论预测了电子转移速率。结果表明,这种自由基阳离子分子的三种异构体的热平均电子转移速率和实验值吻合的较好,而另外一种异构体的电子转移速率是其他三种热平均速率的1000倍!这种异构体的速率可能超出ESR检测范围的,从而为实验测量提供了一种前瞻性的预测。在有机半导体的电荷传输中,结合第一性原理的计算结果和非Condon电子转移速率理论,研究了非Condon效应对二噻吩四硫富瓦烯(DT-TTF)有机半导体迁移率的影响。第一性原理计算的结果表明,只有很少的分子内高频振动模控制着重组能的大小。对于分子间的振动模分析表明,电子耦合强度随核坐标的变化呈现出指数或高斯型而非传统所认为的线型；同时,利用简化的两态模型研究发现,周围近邻分子对“分子对”之间的电子耦合强度有不同程度的影响。对迁移率的计算结果表明在考虑量子协同作用的跳跃模型下,该有机半导体呈现出能带传输特性。非Condon效应的迁移率总是要大于Condon近似的结果。另外,对于DT-TTF晶体,非Condon动态disorder并不明显,这与动力学模拟的结果是一致的。更多还原

【Abstract】 Two kinds of electron transfer (ET) processes in different organic systems are investigated based on first-principles and quantum dynamics methods. One is the intramolecular ET reaction in solution, the other is the charge transport in organic semiconductor.For the intramolecular ET reaction in solution, we take a charge localized intervalence radical cation of a bis(hydrazine) as an example. A variety of ab initio approaches are employed to calculate ET parameters, reorganization energy, electronic coupling and effective frequency, and their validity are also discussed for this system. With use of the obtained parameters, the extend Sumi-Marcus reaction-diffusion theory is adopted to predict the ET rates. The results manifest that the ET rates of three isomers are agreement with the ESR experiment quite well while the rate of the left one is about 1000 times larger than the experimental one. Because of the limitation of ESR experiment, this large rate cannot be measured. Thus, one expects that new techniques have to be used to further investigate it.For the charge transport in organic semiconductor, we have investigated non-Condon effect on the charge carrier mobility of organic semiconductor dithophene-tetrathiathiafulvalene (DT-TTF) crystal. The first-principles calculations reveal that only several high-frequency intramolecular modes dominate the reorganization energy. The nuclear-coordinate dependence of electronic coupling prefers to perform an exponential or Gaussian property for most intermolecular modes rather than a linear one. At the same time, the electronic coupling, which is calculated with the reduced two-state model, of an isolated DT-TTF dimer is indeed affected by the surrounding molecules. Under the hopping mechanism with the nuclear tunneling incorporated, the mobility displays the band-like property. The predicted non-Condon mobility is always greater than that from Condon approximation. Furthermore, we find that the non-Condon dynamic disorder is not important for DT-DDT crystal, which is also confirmed by molecular dynamics simulation.更多还原