Diabatic Representations:New Tools, New Uses and their Application to the Study of Nonadiabatic Processes Influenced by Conical Intersections

约翰霍普金斯大学的David Yarkony得到了化学系化学理论、模型和计算方法项目的一项奖励的支持，该奖项旨在开发新的理论工具来研究分子电子受到激光、太阳或其他来源的光能激发后产生的化学。在太阳能转换、光合作用、视觉，甚至人类DNA对紫外线辐射的稳定性方面，利用光能进行化学都涉及科学家所说的电子非绝热过程，简称非绝热。这种过程涉及代表不同电子态的两个不同势能面的相交。它们本质上是量子力学。虽然现有的计算工具可以描述较小的化学体系的非绝热过程，但仍然缺乏用高精度的理论方法来处理更大、更复杂的体系的方法。Yarkony和他的同事们正在实施旨在将准确描述的范围扩展到更大、更复杂系统的技术。科学界可以免费获得这些技术及其产品。也许最终比这些直接的好处更重要的是，拟议中的工作有可能改变化学物理学家对非绝热的思考方式，并计算其影响。Yarkony利用了近40年前引入的一个开创性的概念，引入了对非绝热性的数学描述的重新表述，这个概念在科学上很贴切，但在其他方面是神秘的，即分子阿哈罗诺夫·玻姆效应。这些对导致光稳定性的非绝热动力学更精确的研究，影响了更广泛的社会目标，即了解与社会相关的过程，例如DNA如何保护自己免受辐射损害。该项目有三个目标：(A)开发一个普遍适用的程序，将几何相结合到支配绝热动力学的单态哈密顿量中，从而能够确定分子Aharonov Bohm效应的普遍性和大小，以及可归因于能量上不可达的锥形交点的几何相对单态核动力学的影响；(B)根据现有的算法和新的工具，建立一个确定多态系统非绝热表示的通用程序，该程序以一般方式将基于性质的非绝热表示合并在一个框架内，该框架明确地包括导数耦合和对虚假(也称为二次)奇点的测试，该奇点可以使基于非绝热的性质无效；和(C)使用现有的代码和在(B)中开发的程序，从准确的电子结构数据构造耦合的非绝热状态表示，以描述生物相关体系中的解离光化学，最初包括苯胺和咪唑。。免费提供的程序和高质量的非绝热哈密顿算符使化学物理学家能够利用这些成果来设计研究工作，以在非绝热化学方面取得进一步进展。GitHub域提供对已发布的非绝热表示的免费访问。

David Yarkony of Johns Hopkins University is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to develop new theoretical tools to study chemistry that arises after a molecule's electrons are excited by light energy from a laser, the sun or another source. The use of light energy to do chemistry in solar energy conversion, photosynthesis, vision and even the stability of human DNA against ultraviolet radiation all involve what scientists call electronically nonadiabatic processes, nonadiabaticity for short. Such processes involve the intersection of two different potential energy surfaces representing different electronic states. They are essentially quantum mechanical. While existing computational tools allow the description of nonadiabatic processes for smaller chemical systems, methods for treating larger, more complex systems with highly accurate theoretical approaches are still lacking. Yarkony and his coworkers are implementing techniques designed to extend the range of accurate descriptions to larger, more complex systems. These techniques and their products, are freely available to the scientific community. Perhaps ultimately even more significant than these immediate benefits, the proposed work has the potential to transform the way chemical physicists think about nonadiabaticity and compute its effects. Yarkony has introduced a reformulation of the mathematical description of nonadiabaticity by exploiting a seminal notion introduced almost 40 years ago, with the scientifically apt, but otherwise arcane appellation, the Molecular Aharonov Bohm effect. These more precise studies of nonadiabatic dynamics leading to photo-stability impact the broader societal goal of understanding societally relevant processes, such as how DNA protects itself against radiation damage. The project has three goals: (a) to develop a generally applicable procedure to incorporate the geometric phase into the single state Hamiltonian governing adiabatic dynamics enabling determination of the prevalence and magnitude of the Molecular Aharonov Bohm effect, the effect of the geometric phase attributable to energetically inaccessible conical intersections on single state nuclear dynamics; (b) to construct from an existing algorithm and new tools, a general program for determining diabatic representations for multi-state systems which incorporates in a general manner properties based diabatizations within a framework which explicitly incorporates derivative couplings and tests for spurious (also termed diabolical) singularities that can invalidate the property based diabatizations; and (c) to use existing code and the program developed in (b) to construct coupled diabatic state representations from accurate electronic structure data to describe dissociative photochemistry in bio-related systems, including initially aniline and imidazole. . The freely available programs and high quality diabatic Hamiltonians enable chemical physicists to use these deliverables to design research efforts to make further progress in nonadiabatic chemistry. A github domain provides free access to the published diabatic representations.