Electronic Structure of Pristine and Highly Doped Conducting Polymers

拟议的研究是面向问题的：他们的目的是了解 在微观层面，从而获得更多的控制， 影响结构和电子的化学因素 高掺杂（良好导电）和原始结构 （半导体）共轭聚合物。 他们的低维 大自然会产生非常大的电子-质子相互作用， 重排，这是电子质子的核心 相互作用和核重排，这是核心的 它们不寻常的电学和光学特性。 由于没有 量子力学方法现在存在，可以处理总的 能量和能带结构的这些系统同时， 选择务实的方法。 它们结合了联合收割机 优化（从头算水平或半经验自 一致场，SCF，用于大单位单元系统的水平） 随后的能带计算使用适当的非 SCF半经验方法。 这些系统中的能量差距是由于核 由化学取代引起的重排和扰动。 将研究范围广泛的聚合物以找到良好的候选物 对于非常小的带隙系统。 Peierls有源畸变 导致梯型聚合物中半导体间隙的模式 受到争议。 计算将决定 这些模式导致最大的能量增益。 在高度 掺杂导电聚合物掺杂剂的位置和取向 将由总能量优化决定。 从头算 计算将确定掺杂剂-聚合物杂化， 链间跳跃相互作用。 的数量方面 掺杂后的键长均衡，包括不对称性 捐赠者和接受者之间的关系将结合 具有新的顺反异构化机理。 流行的 醌型与芳香型的定性概念， 这些聚合物理论的基础，将被放在一个 通过全几何优化的定量基础。 一 小能量新化合物群的系统搜索 有两个或两个以上能量相近的原子核 将尝试配置。

The proposed research is problem oriented: they aim to understand at microscopic level, and thereby gain more control over, the chemical factors which influence the structure and electronic structure of highly doped (well-conducting) and pristine (semiconducting) conjugated polymers. Their low-dimensional nature causes very large electron-proton interactions and nuclear rearrangements, which lie at the core of electron-proton interactions and nuclear rearrangements, which lie at the core of their unusual electrical and optical properties. Since no quantum mechanical method exists now which can treat the total energy and the band structure of these systems simultaneously, a pragmatic approach is chosen. They combine full geometry optimizations (at ab initio level or at semi-empirical self- consistent-field, SCF, level for the large unit cell systems) with subsequent energy band calculations using appropriate non- SCF semi-empirical methods. The energy gaps in these systems are due to the nuclear rearrangements and pertubations caused by chemical substitutions. A broad range of polymers will be studied to find good candidates for very small band gap systems. The Peierls active distortion modes leading to semiconducting gaps in ladder-type polymers have been subject to controversy. Calculations will determine which of these modes leads to the largest energy gain. In the highly doped conducting polymers the location and orientation of dopants will be determined by total energy optimizations. Ab initio calculations will determine the dopant-polymer hybridization and the interchain hopping interaction. The quantitative aspects of bond length equalization upon doping, including the asymetry between donars and acceptors will be determined in conjunction with a new cis-trans isomerization mechanism. The popular qualitative concept of quinoid vs. aromatic forms, which is fundamental in the theory of these polymers, will be put on a quantitative basis through full geometry optimizations. A systematic search for novel groups of compounds with small energy gaps and with two or more energetically close nuclear configurations will be attempted.