Liu Wenlan, Lunkenheimer Bernd, Settels Volker, Engels Bernd, Fink Reinhold F, Köhn Andreas
Institute for Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany.
InnovationLab GmbH, Speyerer St. 4, D-69115 Heidelberg, Germany.
J Chem Phys. 2015 Aug 28;143(8):084106. doi: 10.1063/1.4929352.
We present a general method for analyzing the character of singly excited states in terms of charge transfer (CT) and locally excited (LE) configurations. The analysis is formulated for configuration interaction singles (CIS) singly excited wave functions of aggregate systems. It also approximately works for the second-order approximate coupled cluster singles and doubles and the second-order algebraic-diagrammatic construction methods [CC2 and ADC(2)]. The analysis method not only generates a weight of each character for an excited state, but also allows to define the related quasi-diabatic states and corresponding coupling matrix elements. In the character analysis approach, we divide the target system into domains and use a modified Pipek-Mezey algorithm to localize the canonical MOs on each domain, respectively. The CIS wavefunction is then transformed into the localized basis, which allows us to partition the wavefunction into LE configurations within domains and CT configuration between pairs of different domains. Quasi-diabatic states are then obtained by mixing excited states subject to the condition of maximizing the weight of one single LE or CT configuration (localization in configuration space). Different aims of such a procedure are discussed, either the construction of pure LE and CT states for analysis purposes (by including a large number of excited states) or the construction of effective models for dynamics calculations (by including a restricted number of excited states). Applications are given to LE/CT mixing in π-stacked systems, charge-recombination matrix elements in a hetero-dimer, and excitonic couplings in multi-chromophoric systems.
我们提出了一种通用方法，用于根据电荷转移（CT）和局域激发（LE）构型来分析单重激发态的特征。该分析是针对聚集体系的组态相互作用单重态（CIS）单重激发波函数制定的。它对于二阶近似耦合簇单双激发态方法和二阶代数图示构建方法[CC2和ADC(2)]也大致适用。该分析方法不仅能为激发态生成每个特征的权重，还能定义相关的准绝热态及相应的耦合矩阵元。在特征分析方法中，我们将目标系统划分为不同区域，并分别使用改进的Pipek-Mezey算法在每个区域上对正则分子轨道进行定域化。然后将CIS波函数变换到定域基下，这使我们能够将波函数划分为区域内的LE构型以及不同区域对之间的CT构型。接着通过混合激发态来获得准绝热态，条件是使单个LE或CT构型的权重最大化（在构型空间中进行定域化）。讨论了该过程的不同目标，要么是为了分析目的构建纯LE和CT态（通过包含大量激发态），要么是为了动力学计算构建有效模型（通过包含有限数量的激发态）。给出了该方法在π堆积体系中的LE/CT混合、异二聚体中的电荷复合矩阵元以及多发色团体系中的激子耦合等方面的应用。
