Development, benchmarking and application of improved quantum-classical trajectory surface-hopping methods for the ab initio simulation of photoinduced hydrogen-atom transfer reactions and the computation of time-resolved spectroscopic signals

在多原子分子中涉及非线性耦合的电子势能面的光化学反应动力学的计算处理是具有挑战性的，直到最近才成为可能，由于有效的计算方法的发展和强大的计算资源的可用性。由于电子势能面上的经典核动力学的计算成本仅随自由度的增加而线性增加，因此量子-经典混合计算方法（其中电子被量子力学地描述，而核被经典地描述）对于复杂系统的光化学动力学的模拟是有吸引力的。该项目的目标是进一步开发、基准测试和应用改进的准经典轨道表面跳跃方法，用于非绝热光化学过程的计算模拟和时间分辨光谱信号的计算。在第一个资助期内，我们开发并实现了一种新的鲁棒性和高效的表面跳跃算法，该算法基于Landau-Zener公式，用于计算圆锥形交叉点处的非绝热跃迁概率。这种准经典方法的准确性进行了严格检查，通过与精确的量子动力学计算的多状态多模式模型的光物理和光化学动力学的比较。我们开发了一个计算机程序，用于全维的光化学动力学的飞行模拟与Landau-Zener基于表面跳跃算法，使用二阶代数图解结构（ADC（2））的电子结构方法的从头计算的能量和梯度。在第二个资助期内，我们将超越非平衡电子布居概率的计算，并探索对表现出超快非绝热动力学的系统的时间和频率分辨光谱信号进行精确准经典模拟的可能性。改进的表面跳跃方法的主要化学应用将是从头计算探索碳氮化物材料光催化氧化水所涉及的激发态质子耦合电子转移（PCET）反应，这是目前太阳能转化研究的热点。

The computational treatment of photochemical reaction dynamics involving nonadiabatically coupled electronic potential-energy surfaces in polyatomic molecules is challenging and has only recently become possible due to the development of efficient computational methods and the availability of powerful computing resources. Because the computational cost of classical nuclear dynamics on electronic potential-energy surfaces increases only linearly with the number of degrees of freedom, mixed quantum-classical computational methods, in which the electrons are described quantum mechanically and the nuclei classically, are attractive for the simulation of the photochemical dynamics of complex systems. The goal of this project is the further development, benchmarking and application of improved quasi-classical trajectory surface-hopping methods for the computational simulation of nonadiabatic photochemical processes and the calculation of time-resolved spectroscopic signals. In the first funding period, we developed and implemented a novel robust and efficient surface-hopping algorithm which is based on the Landau-Zener formula for nonadiabatic transition probabilities at conical intersections. The accuracy of this quasi-classical method was critically examined by comparison with exact quantum dynamics calculation for multi-state multi-mode models of photophysical and photochemical dynamics. We developed a computer program for full-dimensional on-the-fly simulations of photochemical dynamics with the Landau-Zener-based surface-hopping algorithm, using the second-order algebraic-diagrammatic construction (ADC(2)) electronic-structure method for the ab initio calculation of energies and gradients. In the second funding period, we will move beyond the computation of nonequilibrium electronic population probabilities and explore the possibility of accurate quasi-classical simulations of time and frequency resolved spectroscopic signals for systems exhibiting ultrafast nonadiabatic dynamics. The main chemical application of the improved surface-hopping method will be the ab initio exploration of excited-state proton-coupled electron transfer (PCET) reactions involved in the photocatalytic oxidation of water with carbon nitride materials, which currently is a hot topic in solar energy conversion research.