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大卫Yarkony是由化学部的化学理论，模型和计算方法计划的奖项支持，以开发新的理论工具来研究分子的电子被激光，太阳或其他来源的光能激发后产生的化学。利用光能来进行太阳能转换、光合作用、视觉甚至人类DNA对紫外线辐射的稳定性等化学反应，都涉及科学家们所说的电子非绝热过程，简称非绝热性。这样的过程涉及代表不同电子状态的两个不同势能面的相交。 它们本质上是量子力学的。 虽然现有的计算工具可以描述较小的化学系统的非绝热过程，但仍然缺乏用高度精确的理论方法来处理更大，更复杂系统的方法。 Yarkony和他的同事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。 这些技术及其产品可供科学界免费使用。 也许最终比这些直接的好处更重要的是，拟议的工作 有可能改变化学物理学家对非绝热性的思考方式，并计算其影响。雅科尼利用了近40年前提出的一个开创性的概念，对非绝热性的数学描述进行了重新表述。这个概念被称为分子阿哈罗诺夫·玻姆效应，在科学上很贴切，但在其他方面却很《双城之战》。 这些对导致光稳定性的非绝热动力学的更精确的研究影响了更广泛的社会目标，即理解社会相关过程，例如DNA如何保护自己免受辐射损伤。该项目有三个目标：（a）发展一种普遍适用的程序，将几何相位纳入控制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，该效应是由能量上不可接近的锥形交叉点对单态核动力学的几何相位的影响;（B）从现有算法和新工具构造，一个通用程序，用于确定非绝热表示的多-状态系统，其以一般方式将基于性质的非绝热化并入明确并入导数耦合的框架内以及测试可以使基于性质的非绝热化无效的伪（也称为恶魔）奇异性;以及（c）使用现有代码和在（B）中开发的程序从精确的电子结构数据构建耦合非绝热态表示，以描述生物相关系统（最初包括苯胺和咪唑）中的解离光化学。. 免费提供的程序和高质量的非绝热哈密顿量使化学物理学家能够使用这些可交付成果来设计研究工作，以在非绝热化学中取得进一步的进展。 一个github域名提供了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.