Electronic Structure of Pristine and Highly Doped Conducting Polymers

建议的研究是面向问题的：他们的目标是在微观水平上了解影响高掺杂(良好导电)和原始(半导体)共轭聚合物的结构和电子结构的化学因素，从而获得更多的控制。它们的低维性质导致了非常大的电子-质子相互作用和核重排，这是电子-质子相互作用和核重排的核心，而电子-质子相互作用和核重排是它们不寻常的电学和光学性质的核心。由于目前还没有一种量子力学方法可以同时处理这些体系的总能量和能带结构，因此选择了一种实用的方法。它们将全几何优化(在从头算水平或在大单胞体系的半经验自洽场水平上)与随后使用适当的非自洽场半经验方法进行的能带计算相结合。这些体系中的能隙是由于化学替代引起的核重排和微扰。将对广泛的聚合物进行研究，以找到非常小带隙系统的良好候选者。导致梯形聚合物半导体带隙的Peierls有源失真模式一直备受争议。计算将确定这些模式中的哪种模式会导致最大的能量增益。在高掺杂的导电聚合物中，掺杂的位置和取向将由总能量优化来决定。从头计算将确定掺杂剂-聚合物杂化和链间跳跃相互作用。我们将结合一种新的顺反异构化机理来确定掺杂后键长均衡的定量方面，包括给体和受体之间的不对称性。在这些聚合物的理论中，常用的喹啉与芳香族形式的定性概念是基本的，将通过充分的几何优化在定量的基础上进行。将尝试系统地寻找具有小能隙和具有两个或两个以上能量接近的核构型的新型化合物基团。

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.