Quantum-Classical Path Integral Methodology

伊利诺伊大学厄巴纳-香槟分校的南希·马克里（Nancy Makri）获得了化学系化学理论，模型和计算方法计划以及计算和数据支持科学与工程计划（CDS E）的奖项，以开发理论和计算方法来描述分子系统中的电子和质子转移过程。电子和质子转移在许多化学和生物反应中起着至关重要的作用。 这些小粒子服从量子力学定律，因此基于经典力学的标准模拟无法正确预测它们的行为。 不幸的是，液体或生物环境中过程的量子力学运动方程的精确解需要巨大的计算能力，而这是不存在的。 Makri正在开发用于模拟这些过程的精确算法;在完全量子力学水平上处理电子或质子，同时通过廉价的经典轨迹捕获系统其余部分的动力学。 这些算法正在计算机代码中实现，这些代码将免费提供给研究界。这项工作的中心主题是量子经典路径积分（QCPI）方法的进一步发展和应用。量子路径的空间局域性和类量子性质使得路径积分框架成为量子经典动力学的理想框架。 所提出的方法利用系统独立的溶剂轨迹的无记忆性来解释量子系统动力学上的所有“经典退相干”效应。 包括剩余的，不太突出的“量子退相干”是通过评估完整的路径积分，这是服从大的时间步长和迭代分解。 应用于溶液和生物分子中的电子和质子转移，将以前所未有的准确性揭示重要的机制。 PI的核心计算机代码QCPI正在与功能强大的分子动力学软件包NAMD和LAMMPS接口。 目标是生产一个计算机包，QCPI-MD，适用于模拟质子，电荷和能量转移过程，具有前所未有的准确性。

Nancy Makri of the University of Illinois Urbana-Champaign is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry division and the Computational and Data-Enabled Science and Engineering Program (CDS&E) to develop theoretical and computational methods to describe electron and proton transfer processes in molecular systems. Electron and proton transfer play a vital role in many chemical and biological reactions. These small particles are subject to the laws of quantum mechanics, and thus standard simulations based on classical mechanics cannot correctly predict their behavior. Unfortunately, the exact solution of the quantum mechanical equations of motion for processes in liquid or biological environments requires enormous computing power that does not exist. Makri is developing accurate algorithms for simulating these processes; treating the electron or proton at the full quantum mechanical level, while capturing the dynamics of the rest of the system via inexpensive classical trajectories. These algorithms are being implemented in computer code which will be freely available to the research community. The central theme of this work is the further development and application of the quantum-classical path integral (QCPI) methodology. The spatially localized, trajectory-like nature of quantum paths makes the path integral framework ideal for quantum-classical dynamics. The proposed methodology exploits the memory-free nature of system-independent solvent trajectories to account for all "classical decoherence" effects on the dynamics of the quantum system. Inclusion of the residual, less prominent "quantum decoherence" is accomplished by evaluating the full path integral, which is amenable to large time steps and iterative decompositions. Application to electron and proton transfer in solution and in biological molecules will shed light on important mechanisms with unprecedented accuracy. The PI's core computer code, QCPI, is being interfaced with the powerful molecular dynamics packages, NAMD and LAMMPS. The goal is to produce a computer package, QCPI-MD, suitable for the simulation of proton, charge and energy transfer processes with unprecedented accuracy.