Li Xin, Parrish Robert M, Liu Fang, Kokkila Schumacher Sara I L, Martínez Todd J
Department of Chemistry and the PULSE Institute, Stanford University , Stanford, California 94305, United States.
SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
J Chem Theory Comput. 2017 Aug 8;13(8):3493-3504. doi: 10.1021/acs.jctc.7b00171. Epub 2017 Jul 12.
The Frenkel exciton model is a useful tool for theoretical studies of multichromophore systems. We recently showed that the exciton model could be used to coarse-grain electronic structure in multichromophoric systems, focusing on singly excited exciton states [ Acc. Chem. Res. 2014 , 47 , 2857 - 2866 ]. However, our previous implementation excluded charge-transfer excited states, which can play an important role in light-harvesting systems and near-infrared optoelectronic materials. Recent studies have also emphasized the significance of charge-transfer in singlet fission, which mediates the coupling between the locally excited states and the multiexcitonic states. In this work, we report on an ab initio exciton model that incorporates charge-transfer excited states and demonstrate that the model provides correct charge-transfer excitation energies and asymptotic behavior. Comparison with TDDFT and EOM-CC2 calculations shows that our exciton model is robust with respect to system size, screening parameter, and different density functionals. Inclusion of charge-transfer excited states makes the exciton model more useful for studies of singly excited states and provides a starting point for future construction of a model that also includes double-exciton states.
弗伦克尔激子模型是用于多发色团体系理论研究的有用工具。我们最近表明，激子模型可用于对多发色团体系中的电子结构进行粗粒化处理，重点关注单重激发激子态[《化学研究述评》2014年，第47卷，2857 - 2866页]。然而，我们之前的方法排除了电荷转移激发态，而电荷转移激发态在光捕获体系和近红外光电器件材料中可能起着重要作用。近期研究也强调了电荷转移在单重态裂变中的重要性，单重态裂变介导了局域激发态与多激子态之间的耦合。在这项工作中，我们报道了一种包含电荷转移激发态的从头算激子模型，并证明该模型能给出正确的电荷转移激发能和渐近行为。与含时密度泛函理论（TDDFT）和方程-of-motion耦合簇理论二阶微扰（EOM-CC2）计算结果的比较表明，我们的激子模型在体系大小、屏蔽参数和不同密度泛函方面具有鲁棒性。包含电荷转移激发态使得激子模型对于单重激发态的研究更有用，并为未来构建同时包含双激子态的模型提供了一个起点。
