复杂体系激发态分子动力学和光谱的理论及其应用

With the recent development of theoretical chemistry and molecular dynamics, there is the great demanding for excited-state molecular dynamics and spectroscopy simulations involving in complex systems. In this case, necessary approximation methods can be classified into two categories: one is classical-trajectory-based method plus various quantum effect corrections and the other is exact-quantum-based method plus various practice mathematic approximations. Trajectory-based nonadiabatic molecular dynamics with its applications in photochemistry belongs to the former, while Franck-Condon theory with its applications in molecular spectra, electron and energy transfer belongs to the latter. Recently, both domestic and foreign research groups have developed various theoretical methods for simulations of nonadiabatic molecular dynamics and molecular spectra. The present propose is focusing on analytically building up nonoadiabatic interference, nonoadiabatic coherence/decohernce and nonoadiabatic tunneling quantum effects into trajectory-based molecular dynamics. Meanwhile, the present propose is focusing on analytically building up Duschinsky, second-order anharmonic, damped-oscillator effects into harmonic Franck-Condon factors. By efficiently and simply combining classical, semiclassical and quantum mechanics methods, we can figure out the new excited-state molecular dynamics and spectroscopy theory aiming for simulation on biology-molecule and material chemical systems in photochemistry.

随着理论化学和动力学的发展，对复杂体系的激发态计算需求日益增加。大体系的计算需要近似处理可以分为两大类型：一类从经典轨迹出发，加上各种量子修正；另一类从精确的量子力学出发，采用数学近似求解量化模型，继而对模型进行修正。非绝热反应动力学在光化学和光物理过程中的应用主要基于第一种手段，Franck-Condon理论及其在电子光谱和能量转移方面的应用主要基于第二种。近些年国内外多个小组发展了不同的方法用于研究非绝热分子动力学和光谱过程。本申请在分子动力学的基础上，通过数学解析的方式，解决各种量子效应，如非绝热的干涉、相干/退相干、量子隧穿效应；另外通过数学解析表达式对Franck-Condon因子进行修正，如Duschinsky效应，非谐效应的一阶和二阶项，溶剂效应，界面效应等。通过将经典、半经典、量子方法三者有效结合，实现对材料和生物体系激发态分子的非绝热动力学和分子光谱的理论模拟和实验应用。

本项目的研究目标是结合各种电子结构量子化学计算方法，提高基于全局跃迁算法（GS-TSH）非绝热动力学方法模拟的速度和精度。将GS-TSH方法扩展到在生物环境，材料环境，界面环境等复杂凝聚态环境下的非绝热动力学和光谱（含和频光谱）的应用。在此项目结题之时，改进了基于全局非绝热开关轨迹表面跳跃法（GS-TSH） 与与含时密度泛函（TDDFT）结合的程序，使其能够快速收敛；实现基于GS-TSH加Gaussian 编制出程序。完成了模拟氧化物的化学反应和光谱，统一处理多重单重电子态间和多重三重电子态间内转换，以及单三态之间系间窜越过程。再结合QM/MM量子化学计算模拟氧化物在溶液中的化学反应和对发光过程最终效率的影响。研究振动和电子和频光谱（SFG）理论模拟方法和应用。并发展了阻尼的Franck–Condon模拟用于解释溶剂增强的吸收和荧光光谱。