Theory and Application of Some New Approaches to Electronically Non-Adiabatic Dynamic

加州大学伯克利分校的William H. Miller和Stephen J. Cotton获得了化学学部化学理论、模型和计算化学项目的奖励，他们开发了模拟各种分子过程的理论方法，这些方法是许多现代技术的基础。这些过程涉及耦合电子态。这样的模拟使研究人员能够更深入地了解这些过程，从而能够以有用的方式修改它们。例如生物分子过程、光电行为和光催化。米勒和科顿正在发展的方法的特点是简单而高效。目标是有一个可靠和易于使用的方法来模拟更大和更复杂的分子系统，而不是目前可能的。本研究的重点是电子非绝热过程，即涉及不同电子状态之间转变的过程。挑战在于如何在一个一致的框架中对待它们耦合的电子自由度和核自由度。该方法使用Meyer-Miller （MM）模型来描述电子自由度，该模型展示了如何将它们“映射”到谐波振荡器上，每个电子状态对应一个谐波振荡器。这就允许将经典分子动力学用于电子学和核自由度。如果所有的自由度都以量子力学的方式处理，MM模型将是精确的。经典地处理它们是一种近似，但通过使用半经典思想来“重新量化”电子自由度通常可以非常准确。这导致了一个惊人的简单对称准经典（SQC）开窗程序的发展，该程序提供了经典迈耶-米勒（MM）振动动力学中电子振荡器自由度（DOF）的半经典“量化”。这种SQC/MM方法的重要基准测试已被视为给出半经典（因此类似量子）的结果，但这样做的数量级比真正的半经典计算更有效，当然，没有完整量子动力学模拟的固有指数缩放成本。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

William H. Miller and Stephen J. Cotton of the University of California, Berkeley are supported by an award from the Chemical Theory, Models and Computational Chemistry Program in the Division of chemistry to develop theoretical methods for simulating a variety of molecular processes that are fundamental to many modern technologies. These processes involve coupled electronic states. Such simulations allow researchers to understand these processes more deeply and thus be able to modify them in useful ways. Examples are biomolecular processes, photovoltaic behavior, and photo-catalysis. The approach that Miller and Cotton is developing is characterized by its simplicity and its efficiency. The goal is to have a reliable and easy to use approach for simulating larger and more complex molecular systems than is what is currently possible. The specific focus of this research is electronically non-adiabatic processes, i.e., those that involve transitions between different electronic states. The challenge is to treat the electronic degrees of freedom and the nuclear degrees of freedom, to which they are coupled, in a consistent framework. The approach uses the Meyer-Miller (MM) model for the electronic degrees of freedom, which shows how they can be "mapped" onto harmonic oscillators, one for each electronic state. This then allows the use of classical molecular dynamics for electronics as well as nuclear degrees of freedom. The MM model would be exact if all the degrees of freedom were treated quantum mechanically. Treating them all classically is an approximation but can often be very accurate by using semiclassical ideas to "re-quantize" the electronic degrees of freedom This has resulted in the development of a striking simple symmetrical quasi-classical (SQC) windowing procedure that provides a semiclassical-like "quantization" of the electronic oscillator degrees-of- freedom (DOF) in classical Meyer-Miller (MM) vibronic dynamics. Significant benchmarking of this SQC/MM approach has been seen to give semiclassical-like (and therefore quantum-like) results, but to do so orders of magnitude more efficiently than a true semiclassical calculation and, of course, without the inherent exponentially scaling cost of a full quantum dynamics simulationThis 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.