CAREER: Investigation of Laser-driven Chemical Reactions by Molecular Dynamics

北达科他州立大学的德米特里·基林（Dmitri Kilin）获得了化学系化学理论、模型和计算方法项目的奖项，他的理论研究重点是控制由光驱动的化学反应，即光反应。光可以激活、指导和加速化学反应，这是热等传统反应条件无法实现的。本研究的目的是研究和模拟通过调谐专用激光来控制光化学反应。这些研究人员开发了可分发的软件，用户可以用它来探索光驱动的化学反应。该软件将有助于推进广泛的技术，包括能量转换和存储，以及化学传感。这项工作将有助于薄膜沉积技术的理论指导优化，这对电子电路向纳米和亚纳米尺度的小型化具有重要意义。教育任务包括研究生和本科生参与专业活动。外联活动的重点是通过参与NDSU的培养美国部落本科生研究和教育（NATURE）计划，为印第安人保留地的部落大学生提供研究经验，这将特别受益于远程/远程学习/培训/研究机会。Kilin博士还将指导参加nsu举办的PICNICS（父母与孩子一起参与，培养科学中的求知欲）计划的高中生。由于电子和核的耦合自由度，电磁场下动力学的计算描述仍然具有挑战性。有一些已知的方法可以独立处理后续的贡献过程：光激发、重组和与电子自由度的耗散相互作用，以及核自由度的分子和反应动力学。然而，在短时间内，这三者是相互关联的。Kilin小组正在开发耦合电子、原子核和光的第一性原理分子动力学方法，以填补激光驱动化学反应计算研究的空白。该方法依赖于Rabi理论和表面跳跃近似的结合。研究计划包括验证所使用的近似的努力。假设驱动的可接受近似值的搜索显示精度与数值成本有助于建立极端条件下反应的标准方法。考虑到核自由度的量子化、电子结构计算精度的提高和量子化态相干叠加的处理，正在实施各种修正。改进方法的实际应用主要集中在金属有机化合物的光破碎、含硅化合物的光聚合、共价官能团在碳纳米管上的光接枝和光解吸。正在开发的理论工具可以适用于解释和预测各种反应的反应机理和产物分布。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。

Dmitri Kilin of North Dakota State University is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry for theoretical research focused on the control of chemical reactions driven by light, called photoreactions. Light can activate, direct, and speed up chemical reactions otherwise inaccessible by conventional reaction conditions like heat. The goal of this research is to study and simulate the control of photochemical reactions through the tuning of specialized laser light. These researchers develop distributable software with which users can explore light-driven chemical reactions. The software will help advance a wide range of technologies, including energy conversion and storage, and chemical sensing. This work will contribute to theory-guided optimization of thin-film deposition technology, which is important for the miniaturization of electronic circuits towards nano- and sub-nano scales. The educational mission includes the participation of graduate and undergraduate students in professional activities. Outreach activities are focused on providing to tribal college students at Native American reservations research experience via participations in the Nurturing American Tribal Undergraduate Research and Education (NATURE) Program at NDSU, which will specifically benefit from remote/distant learning/training/research opportunities. Dr. Kilin will also mentor high school students participating in PICNICS (Parents Involvement with Children, Nurturing Intellectual Curiosity in Science) program hosted at NDSU.The computational description of dynamics under the electromagnetic field remains challenging due to coupled electronic and nuclear degrees of freedom. There are known approaches for independent treatment of subsequent contributing processes: photoexcitation, reorganization and dissipative interaction with electronic degrees of freedom, and molecular and reaction dynamics of nuclear degrees of freedom. However, on a short timescale, all three are coupled. The Kilin group is developing first-principles molecular dynamics approaches for coupled electrons, nuclei, and light to fill the gap in computational investigation of laser-driven chemical reactions. The approaches rely on the combination of Rabi theory and surface hopping approximations. The research program includes an effort for validation of utilized approximations. A hypothesis driven search of acceptable approximations showing accuracy versus numerical cost facilitates an effort of establishing standard approaches for reactions at extreme conditions. Various corrections are being implemented accounting for the quantization of nuclear degrees of freedom, the higher level of electronic structure calculations with increased precision, and the treatment of coherent superposition of quantized states. The practical applications of the improved methodologies focus on photofragmentation of metal-organic compounds, photopolymerization of silicon containing compounds, photografting, and photodesorption of covalent functional groups on carbon nanotubes. The theoretical tools being developed can be applicable to interpret and predict reaction mechanisms and distribution of products for various classes of reactions.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.