Kim Chang Woo, Choi Bongsik, Rhee Young Min
Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea.
Phys Chem Chem Phys. 2018 Jan 31;20(5):3310-3319. doi: 10.1039/c7cp06303b.
We analyze the environment-induced fluctuation of pigment excitation energies in the Fenna-Matthews-Olson (FMO) complex from various perspectives, by employing an interpolation-based all-atom potential energy model for describing realistic pigment vibrations. We conduct molecular dynamics simulations on a 100 ns timescale, which is an extent that can enclose the effect of static disorder, and demonstrate its timescale separation from fast dynamic disorder. We extract the spectral densities of the complex by considering both the site and the exciton bases. We show that exciton delocalization reduces the effective environmental fluctuation and rationalize this aspect based on a model of fluctuating molecular aggregates. We also obtained the spectral density of the lowest exciton state under low temperature conditions and show that it reasonably well reproduces the experimental result. Finally, by additionally performing non-equilibrium excited state trajectory simulations, we show that the system lies well within the linear response regime after photo-absorption and that the pigments do not visit anharmonic regions of the potential surface to a significant extent. This indicates that methodologies based on harmonic bath models are indeed reasonable approaches for describing the excited state dynamics of the FMO complex.
我们从多个角度分析了芬纳 - 马修斯 - 奥尔森（FMO）复合物中色素激发能的环境诱导波动，采用基于插值的全原子势能模型来描述实际的色素振动。我们在100纳秒的时间尺度上进行分子动力学模拟，这一尺度能够涵盖静态无序的影响，并证明其时间尺度与快速动态无序的分离。我们通过考虑位点和激子基来提取复合物的光谱密度。我们表明激子离域降低了有效的环境波动，并基于波动分子聚集体模型对这一方面进行了合理化解释。我们还获得了低温条件下最低激子态的光谱密度，并表明它能合理地重现实验结果。最后，通过额外进行非平衡激发态轨迹模拟，我们表明光吸收后系统处于线性响应区域内，并且色素在很大程度上不会进入势能面的非谐区域。这表明基于谐波浴模型的方法确实是描述FMO复合物激发态动力学的合理方法。
