Approximate Quantum Mechanical Methods for Excited State Potential Energy Surface Exploration

化学系的化学理论、模型和计算方法项目将支持堪萨斯州立大学（KSU）的Christine Aikens博士开发量子力学方法，使研究大型生物分子和纳米颗粒的光化学过程成为可能。这些研究在生物医学成像、光化学和太阳能转换等领域具有广阔的应用前景。如果没有这些方法，目前还无法准确地研究具有数百个原子的大型系统的激发态过程。本研究开发的方法将首次实现对大型生物分子和纳米颗粒的激发态势能的探测。这将允许检查这些系统中的能量转移途径和光发射。通过GROW（女孩研究我们的世界，6 -8年级）和EXCITE！（探索科学，技术和工程，9 -12年级）KSU的初中和高中女生课程将培养参与者对STEM，特别是计算化学的持续兴趣。这项工作也将在Science cafims上以普通观众为目标进行展示。Christine Aikens和她的研究小组正在开发一套基于时间依赖密度泛函理论（TDDFT）的近似方法，与目前的TDDFT方法相比，该方法可以以低50到60倍的计算成本计算激发态能量和梯度。这些方法将包括预计对自由基和三重态有效的开壳版本，以及包括Hartree-Fock交换的版本，旨在准确地处理电荷转移激发。还将开发包括分数占位数的方法，这将有利于具有非常小的HOMO-LUMO间隙的大型金属纳米颗粒等系统。这些计算方法有望对生物成像方法的发展、光化学研究和太阳能转换研究产生更广泛的科学影响，在这些研究中，核弛豫和激发态势能表面的动力学对于预测发光发射波长、反应途径和能量转移途径至关重要。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 this award, the Chemical Theory, Models and Computational Methods program in the Division of Chemistry is supporting Dr. Christine Aikens of Kansas State University (KSU) to develop quantum mechanical methods that will enable the study of photochemical processes in large biological molecules and nanoparticles. There are broad potential applications of these studies to the fields of biomedical imaging, photochemistry, and solar energy conversion. Without these methods, it is currently not feasible to study excited state processes in large systems with hundreds of atoms accurately. The methods being developed in this work will enable excited state potential energy exploration of large biological molecules and nanoparticles for the first time. This will allow the examination of energy transfer pathways and light emission in these systems. Outreach efforts through the GROW (Girls Researching Our World, 6th-8th grade) and EXCITE! (EXploring sCIence, Technology, and Engineering, 9th-12th grade) programs at KSU for middle and high school girls will foster a continuing interest in STEM, particularly computational chemistry, among the participants. This work will also be presented at Science Cafés at a level aimed at a general audience.Dr. Christine Aikens and her research group are developing a suite of approximate methods based on time-dependent density functional theory (TDDFT) that will enable the calculation of excited state energies and gradients at about 50 to 60 times lower computational cost compared to current TDDFT methods. These methods will include open-shell versions that are expected to be effective for radicals and triplet states, as well as versions that include Hartree-Fock exchange that are designed to accurately treat charge-transfer excitations. Methods that include fractional occupation numbers will also be developed, which will be beneficial for systems such as large metal nanoparticles that have a very small HOMO-LUMO gap. These computational methods are expected to have broader scientific impacts on biological imaging methods development, photochemistry studies, and upon solar energy conversion research, endeavors in which nuclear relaxation and dynamics on excited state potential energy surfaces are critical for predicting luminescence emission wavelengths,reactive pathways, and energy transfer pathways.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.