Combining the quasi-classical mapping Hamiltonian approach with the generalized quantum master equation to simulate nonadiabatic molecular dynamics and its spectroscopic signature

密歇根大学的Eitan Geva获得了化学系化学理论、模型和计算方法项目的奖励，他开发了新的理论和计算方法来建模和模拟涉及多个电子态的分子系统。在这些系统中，一些电子被激发。在低能电子态和高能激发态之间存在耦合。化学家把这些系统的动力学称为“非绝热”分子动力学。非绝热动力学在生物过程中是重要的，例如细胞呼吸和光合作用。它们在能源储存和光伏等新兴技术中也很重要。这些系统也很难模拟，因为非绝热动力学本质上是量子力学的。实际上，量子计算的计算成本非常高，即使是目前最先进的计算机也无法实现。然而，经典分子动力学的计算机模拟对于大型和复杂的分子系统是具有成本效益的。Geva小组正在开发一种方法，使用所谓的“半经典”方法，以类似经典的计算成本准确可靠地模拟非绝热动力学。Geva博士还参与了物理化学课程现代化和改进的活动，并进一步开发了一种新的计算机学习教学法。该方法结合了用于模拟多态分子系统的电子非绝热动力学的准经典映射哈密顿方法，用于描述电子自由度的简化动力学的广义量子主方程，以及用于计算非线性时间分辨光谱信号的光响应理论。将上述三个组成部分（拟经典映射哈密顿量、广义量子主方程和光响应理论）综合起来，就形成了一种强大的方法，这是弥合理论与实验之间差距所必需的。它允许人们以一种准确、经济、自洽的方式计算实验相关的量，如电子跃迁率和非线性时间分辨光谱信号，从明确的分子模型开始，其中核自由度的动力学由非谐波电子态特定力场控制。方法的发展是在几个模型系统的背景下进行的，这些模型系统的分子细节水平不断提高，包括两态供体-受体基准模型、光合反应中心模型和液体溶液中的三元和二元模型。应当指出的是，上述方法是一般性的，并不局限于它所根据的系统。这些方法通过出版物、专业会议上的演讲、与实验组的合作以及NSF持续创新软件基础设施项目广泛传播。小组成员接受广泛的培训，为他们在学术机构、政府实验室或行业的独立职业生涯做好准备。该研究项目还通过加强计算组和实验组之间的关系，使物理化学课程现代化，并在同行领导的荣誉工作室中推进新的计算机学习教学法，在那里注册物理化学入门本科课程的学生创建交互式计算机演示来演示物理化学概念，从而为大学的教学使命做出贡献。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。

Eitan Geva of the University of Michigan is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to develop new theoretical and computational approaches to model and simulate molecular systems involving more than one electronic state. In these systems, some of the electrons are excited. There is coupling between the lowest energy electronic state and higher energy excited states. Chemists refer to the dynamics of these systems as "nonadiabatic" molecular dynamics. Nonadiabatic dynamics are important in biological processes, for example cellular respiration and photosynthesis. They are also important in emerging technologies such as energy storage and photovoltaics. These systems also very difficult to simulate because nonadiabatic dynamics are inherently quantum-mechanical. Truly quantum calculations have a very large computational cost which puts them beyond the reach of even the most advanced currently available computers. Computer simulations of classical molecular dynamics, however, are cost-effective for large and complex molecular systems. The Geva group is developing a methodology for simulating nonadiabatic dynamics accurately and reliably at classical-like computational cost, using what is called a "semiclassical" approach. Dr. Geva is also involved in activities to modernize and improve the physical chemistry curricula and to further develop a new Compute-to-Learn pedagogy.The methodology combines the quasi-classical mapping Hamiltonian approach for modeling the electronically nonadiabatic dynamics of a multi-state molecular system with the generalized quantum master equation, for describing the reduced dynamics of the electronic degrees of freedom, and optical response theory, for calculating nonlinear time-resolved spectral signals. The synthesis of the above-mentioned three components (the quasi-classical mapping Hamiltonian, generalized quantum Master equation and optical response theory) leads to a powerful methodology, which is necessary to bridge the gap between theory and experiment. It does so by allowing one to calculate experimentally relevant quantities like electronic transition rates and nonlinear time-resolved spectral signals in an accurate, cost-effective and self-consistent manner, starting from explicitly molecular models, where the dynamics of the nuclear degrees of freedom is governed by anharmonic electronic-state-specific force fields. Method development takes place in the context of several model systems with increasing level of molecular detail, including two-state donor-acceptor benchmark models, models of photosynthetic reaction centers and models of triads and dyads in liquid solution. It should be noted that the above-mentioned methodology is general and not limited to the systems in the context of which it is being developed. The methods are disseminated broadly via publications, presentations in professional meetings, collaborating with experimental groups and the Software Infrastructure for Sustained Innovation NSF program. Group members receive extensive training that prepares them for an independent career in an academic institution, government lab or industry. This research program also contributes to the university teaching mission via strengthening the relationship between computational and experimental groups, modernizing curricula of physical chemistry courses, and advancing a new Compute-to-Learn pedagogy within a peer-led honors studio where students registered to introductory physical chemistry undergraduate courses create interactive computer demos that demonstrate physical chemistry concepts.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.