Collaborative Research: Theoretical Description of Electron-driven Chemical Processes and Related Reactions

在化学系化学理论、模型和计算方法（CTMC）项目的支持下，普渡大学的Chris Greene和中佛罗里达大学（UCF）的Viatcheslav kokouline将合作解决一类与电子与具有物理或生化相关性的分子碰撞有关的量子力学问题。当一个低能电子撞击一个分子时，会产生几种可能的结果，包括键断裂导致分裂成更小的分子和原子。这类物理化学过程已被证明是极具挑战性的，目前的理论方法来描述。为了克服目前理论的局限性，Greene和Kokoouline将应用一套数学和计算工具来确定这种断键反应发生的速率。了解这些电子引发的化学过程的需求在几个不同的领域产生了共鸣，包括化学天体物理学、等离子体化学和辐射生物化学。对慢电子撞击DNA（2'-脱氧核糖核酸）时触发的事件序列的深入了解将有助于理解单链或双链断裂是如何发生的。虽然量子力学的原理被普遍理解，但应用这些原理来处理这种复杂性的理论问题并准确计算碰撞结果是极其困难的，该领域将受益于该项目所开发的改进。更广泛的教育影响来自对学生的培训，包括研究生和本科生，以及博士后学者，使他们具备解决该子领域难题所需的计算和理论工具。这项由dr。普渡大学的Chris Greene和UCF的Viatcheslav kokouline将分别专注于一组选定的目标分子系统，这些系统被选中作为这些非扰动化学过程的原型，在这些过程中，能量从电子自由度转化为解离自由度。这里提出的研究旨在提高处理物理化学问题的理论能力，这些问题超出了该领域的通常范式，即玻恩-奥本海默近似。场的正规规则首先通过计算一个电子势面，或在某些情况下几个这样的耦合面来处理任何反应过程，作为核坐标的函数，然后在时变或时变量子力学中求解与这些表面上的运动有关的耦合微分或偏微分方程。虽然这个主题在处理反应化学和光化学过程方面取得了许多成功，但电子驱动的化学转化继续对现有理论提出严峻挑战。因此，Greene/ kokouline团队将努力在两个截然不同的方向上推进当前的理论方法。首先，电子计算将随着三维有限元计算的探索而发展，有效的电子-分子相互作用势模型与通过引入包含密度泛函理论势的静态势近似包含的相关性。其次，计算方法将得到显著改进，以便能够计算发生在大分子中的键断裂，特别是那些具有生物学相关性的键断裂。在UCF团队的支持下，Viatcheslav kokouline还将开发一个基于网络的平台和相关方法，以工作室模式教授量子力学，然后将其提供给社区。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

WIth support from the Chemical Theory, Models and Computational Methods (CTMC) Program in the Division of Chemistry, Chris Greene of Purdue University and Viatcheslav Kokoouline of the University of Central Florida (UCF) will collaboratively work to solve a class of quantum mechanical problems related to electron collisions with molecules having physical or biochemical relevance. When a low energy electron strikes a molecule, several possible outcomes can occur, including bond breakage leading to fragmentation into smaller molecules and atoms. This class of physico-chemical processes has proven to be extremely challenging for current theoretical methods to describe. To overcome current limitations of theory, Greene and Kokoouline will apply a mathematical and computational set of tools to determine the rate at which such bond-breaking reactions occur. The need to understand these electron-initiated chemical processes resonates across several disparate fields, including chemical astrophysics, plasma chemistry, and radiation biochemistry. A deeper understanding of the sequence of events that is triggered when a slow electron impacts DNA (2'-deoxyribonucleic acid) will help to understand how single or double strand breaks occur. While the principles of quantum mechanics are understood generally, applications of those principles to treat theoretical problems of this complexity and to compute collision outcomes accurately are extremely difficult and the field will benefit from the improvements to be developed by this project. An educational broader impact derives from the training of students, both graduate and undergraduate, as well as postdoctoral scholars, engendering them with the computational and theoretical tools needed to tackle difficult problems in this subfield.This collaborative research effort by Drs. Chris Greene and Viatcheslav Kokoouline of Purdue University and UCF, respectively, will concentrate on a select set of target molecular systems, selected to serve as prototypes of these non-perturbative chemical processes in which energy is converted from electronic into dissociative degrees of freedom. The research proposed here aims to improve theoretical capabilities for treating problems in physical chemistry that go beyond the usual paradigm of the field, which is the Born-Oppenheimer approximation. The normal rubric of the field treats any reactive process initially by computing one electronic potential surface, or in some cases a few such surfaces with couplings, as a function of the nuclear coordinates, followed by solution of coupled differential or partial differential equations relating to motion on those surfaces in either time-dependent or time-independent quantum mechanics. While this rubric has yielded many successes in treating reactive chemical and photochemical processes, electron-driven chemical transformations continue to pose severe challenges to existing theory. Therefore the Greene/Kokoouline team will endeavor to advance current theoretical approaches in two largely separate directions. Firstly, the electronic calculation will be developed with explorations of three-dimensional finite-element calculations with effective electron-molecule interaction potentials modeled with correlations approximately included through the introduction of static potentials that incorporate density-functional theory potentials. Secondly, the computational methods will be significantly improved to enable calculations of the bond-breaking that occurs in large molecules, especially those having biological relevance. In an outreach activity supported by the UCF team, Viatcheslav Kokoouline will also develop a web-based platform and a related methodology to teach quantum mechanics in studio-mode like classes that will then be made available to the community.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.