CAREER: Photochemistry with Resonating Mean-Field

在化学学部化学理论、模型和计算方法（CTMC）项目的支持下，凯斯西储大学的谢恩·帕克将推进光引发的化学反应的模拟。利用或产生光的化学反应被称为光化学反应，是许多技术和生物学重要过程的核心，包括光催化、太阳能电池发电和紫外线引起的DNA损伤。为了可靠地设计新的光催化剂或光敏剂，研究人员需要了解光化学反应的微观机制。基于量子力学的模拟是揭示复杂光化学反应机制的有力工具。然而，光化学模拟的适用性受到现有方法质量的限制。帕克博士和他的研究小组正在开发用于光化学模拟的共振平均场方法，从而提高了当前最先进方法无法达到的反应类别的模拟精度。该项目包括对理论化学的本科生和研究生进行培训和指导，并参与美国化学会项目SEED，从克利夫兰地区的学校招募高中生进行暑期研究。此外，帕克博士将建立一套以教育为重点的程序，可以在网络浏览器中运行，这样K-12学生和大学生就可以在课堂上使用数值模拟来询问化学模型。第一性原理模拟已经成为一种强大的工具，用于发现复杂光化学反应的微观机制，这是社会面临的许多重大挑战的核心，例如利用二氧化钛纳米颗粒生产太阳能燃料。然而，由于缺乏负担得起的量子化学方法来平衡具有不同电荷和自旋特征的电子状态的描述，这种模拟在广泛问题中的应用目前受到阻碍。为了满足这一需求，帕克博士和他的研究小组正在开发用于光化学模拟的共振平均场（ResMF）方法。ResMF是一种很有前途的光化学模拟方法，因为它具有平均场成本，明确地平衡具有不同特征的状态，并再现了圆锥形相交的正确拓扑结构。本提案的研究目标是i)建立一种非正交自旋适应波函数展开，以消除自旋污染并降低计算成本，ii)产生一个数值上鲁棒且有效的ResMF实现，以及iii)实现模拟光化学所需的所有分子力和性质。该提案的教育目标是i)开发基于网络的数值模拟工具，用于所有级别的课堂；ii)培训K-12教育工作者教授基于模型的思维技能；iii)向克利夫兰地区学校的高中生介绍科学研究。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, Shane Parker of Case Western Reserve University will advance simulations of chemical reactions triggered by light. Chemical reactions that use or produce light are called photochemical reactions and are at the heart of many technologically and biologically important processes including photocatalysis, electricity generation in solar cells, and DNA damage caused by ultraviolet light. To reliably design new photocatalysts or photosensitizers, researchers need to understand the microscopic mechanism of photochemical reactions. Simulations based on quantum mechanics are a powerful tool for unraveling the mechanism of complicated photochemical reactions. However, the applicability of photochemistry simulations is limited by the quality of the available methods. Dr. Parker and his research group are developing the Resonating Mean-Field method for use in photochemistry simulations, thus enabling simulations with improved accuracy for classes of reactions that are inaccessible to current state-of-the-art methods. This project involves training and mentoring undergraduate and graduate students in theoretical chemistry and engagement with the Americal Chemical Society Project SEED to recruit high school students from Cleveland-area schools for summer research. In addition, Dr. Parker will build a suite of education-focused programs that run in web browsers so that K-12 students and university students can use numerical simulations to interrogate chemical models in the classroom.First-principles simulations have emerged as a powerful tool to discover the microscopic mechanism of complex photochemical reactivities at the heart of many important grand challenges for society, such as solar-fuel production on titanium dioxide nanoparticles. However, the use of such simulations for broad classes of problems is currently thwarted by the lack of affordable quantum chemistry methods that can balance the descriptions of electronic states with different charge and spin characteristics. To address this need, Dr. Parker and his research group are developing the Resonating Mean-Field (ResMF) method for photochemistry simulations. ResMF is a promising method for photochemistry simulations because it has a mean-field cost, explicitly balances states with different characters and reproduces the correct topology of conical intersections. The research objectives of this proposal are i) to establish a nonorthogonal spin-adapted wavefunction expansion that eliminates spin-contamination and reduces computational cost, ii) to produce a numerically robust and efficient implementation of ResMF, and iii) to implement all molecular forces and properties necessary to simulate photochemistry. The educational objectives of this proposal are i) to develop web-based numerical simulation tools for use in classrooms of all levels, ii) to train K-12 educators to teach model-based thinking skills, and iii) to introduce high school students from Cleveland-area schools to scientific research.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.