Maity Sayan, Bold Beatrix M, Prajapati Jigneshkumar Dahyabhai, Sokolov Monja, Kubař Tomáš, Elstner Marcus, Kleinekathöfer Ulrich
Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany.
Institute of Physical Chemistry, Karlsruhe Institute of Technology, Kaiserstrasse 12, 76131 Karlsruhe, Germany.
J Phys Chem Lett. 2020 Oct 15;11(20):8660-8667. doi: 10.1021/acs.jpclett.0c02526. Epub 2020 Sep 29.
Because of the size of light-harvesting complexes and the involvement of electronic degrees of freedom, computationally these systems need to be treated with a combined quantum-classical description. To this end, Born-Oppenheimer molecular dynamics simulations have been employed in a quantum mechanics/molecular mechanics (QM/MM) fashion for the ground state followed by excitation energy calculations again in a QM/MM scheme for the Fenna-Matthews-Olson (FMO) complex. The self-consistent-charge density functional tight-binding (DFTB) method electrostatically coupled to a classical description of the environment was applied to perform the ground-state dynamics. Subsequently, long-range-corrected time-dependent DFTB calculations were performed to determine the excitation energy fluctuations of the individual bacteriochlorophyll molecules. The spectral densities obtained using this approach show an excellent agreement with experimental findings. In addition, the fluctuating site energies and couplings were used to estimate the exciton transfer dynamics.
由于光捕获复合物的尺寸以及电子自由度的参与，从计算角度来看，这些系统需要采用量子 - 经典联合描述来处理。为此，在基态下以量子力学/分子力学（QM/MM）方式采用玻恩 - 奥本海默分子动力学模拟，随后再次以QM/MM方案对费纳 - 马修斯 - 奥尔森（FMO）复合物进行激发能计算。将自洽电荷密度泛函紧束缚（DFTB）方法与环境的经典描述进行静电耦合，用于执行基态动力学。随后，进行长程校正的含时DFTB计算，以确定各个细菌叶绿素分子的激发能波动。使用这种方法获得的光谱密度与实验结果显示出极好的一致性。此外，波动的位点能量和耦合用于估计激子转移动力学。
