The Development of Spin-Adiabatic Approaches for Studying Spin-Crossing Reactions

在化学系化学理论、模型和计算方法（CTMC）项目和促进竞争性研究的既定项目（EPSCoR）的支持下，俄克拉何马大学的邵毅涵和杨志波将开发研究自旋交叉反应的自旋绝热方法。自旋交叉反应是广泛的化学、生化和光化学过程的核心，如气相离子-分子反应、过渡金属络合物催化、氧活化、自然和人工水分解、化学发光/生物发光。然而，由于以下几个原因，对自旋交叉反应进行建模仍然极具挑战性：这类反应的复杂性；同时探索多个自旋非绝热势能面的困难缺乏足够的方法/软件支持来有效地识别自旋交叉反应能量途径（和反应自由能途径）并准确预测其反应速率。为了克服这一挑战，Shao和Yang团队将开发一种准确、高效和开源的计算方案，用于直接在最低能量的自旋绝热势能表面上研究自旋交叉反应。根据该计划开发的软件将以自由和开源的方式发布。根据该奖项，该团队还主持了一个qm-mm.org网站，并每月举办网络研讨会，为年轻的研究人员提供学习计算化学工具最新应用的机会。Shao博士，Yang博士和他们在俄克拉何马大学的研究团队正在开发构建和探索自旋绝热表面的方法，以便在过渡态搜索或分子动力学模拟中可以自动平稳地从高自旋状态过渡到低自旋状态（反之亦然）。本研究的目标是：(a)实现多重自旋轨道耦合和自旋交叉概率方案；(b)解析能量梯度公式；(c)通过混合量子力学分子力学模型纳入环境效应；(d)结合路径优化方法进行自由能计算；(e)利用主动空间或耦合簇量子化学计算对选定构型的能量和自由能结果进行改进；(f)评估高能自旋绝热激发态的贡献。该团队将把这些新的计算方法应用于质谱仪实验中研究的几个自旋交叉离子-分子反应。他们还将研究化学发光和生物发光中的氧化反应，以获得机理见解。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 and the Established Program to Stimulate Competitive Research (EPSCoR), Yihan Shao and Zhibo Yang of the University of Oklahoma will develop spin-adiabatic approaches for studying spin-crossing reactions. Spin-crossing reactions are central to a wide range of chemical, biochemical, and photochemical processes such as gas-phase ion-molecule reactions, transition metal complex catalysis, oxygen activation, natural and artificial water splitting, and chemiluminescence/bioluminescence. However, it remains extremely challenging to model spin-crossing reactions due to several reasons: complex nature of such type of reactions; difficulties of simultaneously exploring multiple spin-diabatic potential energy surfaces; lack of sufficient methodology/software support for efficiently identifying spin-crossing reaction energy pathway (and reaction free energy pathway) and for accurately predicting their reaction rates. To overcome this challenge, the Shao and Yang groups will develop an accurate, efficient, and open-source computational protocol for studying spin-crossing reactions directly on the lowest-energy spin-adiabatic potential energy surface. Software developed under this program will be released in a free and open-source manner. Under this award, the team also host a qm-mm.org website and hold monthly webinars to provide young researchers an opportunity to learn from the latest applications of computational chemistry tools. Dr. Shao, Dr. Yang and their research teams at the University of Oklahoma are developing methods to construct and explore spin-adiabatic surfaces, so that one can transition automatically and smoothly from a high-spin state to a lower-spin one (or vice versa) during a transition state search or molecular dynamics simulation. This research is projected to proceed with the following objectives: (a) implementation of multiple spin-orbit coupling and spin- crossing probability schemes; (b) formulation of analytical energy gradients; (c) incorporation of environment effects through hybrid quantum mechanical molecular mechanical models; (d) combination with pathway optimization methods in free energy calculations; (e) improvement to the energy and free energy results with active-space or coupled-cluster quantum chemistry calculations on selected configurations; and (f) assessment of the contribution from higher-energy spin-diabatic excited states. The team will apply these new computational methods to several spin-crossing ion-molecule reactions studied with mass spectrometry experiments. They will also investigate oxygenation reactions in chemiluminescence and bioluminescence to gain mechanistic insights.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.