Bao Peng, Hettich Christian P, Shi Qiang, Gao Jiali
Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455, United States.
J Chem Theory Comput. 2021 Jan 12;17(1):240-254. doi: 10.1021/acs.jctc.0c01015. Epub 2020 Dec 28.
We describe a block-localized excitation (BLE) method to carry out constrained optimization of block-localized orbitals for constructing valence bond-like, diabatic excited configurations using multistate density functional theory (MSDFT). The method is an extension of the previous block-localized wave function method through a fragment-based ΔSCF approach to optimize excited determinants within a molecular complex. In BLE, both the number of electrons and the electronic spin of different fragments in a whole system can be constrained, whereas electrostatic, exchange, and polarization interactions among different blocks can be fully taken into account of. To avoid optimization collapse to unwanted states, a ΔSCF projection scheme and a maximum overlap of wave function approach have been presented. The method is illustrated by the excimer complex of two naphthalene molecules. With a minimum of eight spin-adapted configurational state functions, it was found that the inversion of and states near the optimal structure of the excimer complex is correctly produced, which is in quantitative agreement with DMRG-CASPT2 calculations and experiments. Trends in the computed transfer integrals associated with excited-state energy transfer both in the singlet and triplet states are discussed. The results suggest that MSDFT may be used as an efficient approach to treat intermolecular interactions in excited states with a minimal active space (MAS) for interpretation of the results and for dynamic simulations, although the selection of a small active space is often system dependent.
我们描述了一种块局域激发（BLE）方法，用于利用多态密度泛函理论（MSDFT）对块局域轨道进行约束优化，以构建类似价键的绝热激发构型。该方法是通过基于片段的ΔSCF方法对先前的块局域波函数方法的扩展，用于优化分子复合物中的激发行列式。在BLE中，可以约束整个系统中不同片段的电子数和电子自旋，同时可以充分考虑不同块之间的静电、交换和极化相互作用。为了避免优化陷入不需要的状态，提出了一种ΔSCF投影方案和波函数最大重叠方法。通过两个萘分子的准分子复合物对该方法进行了说明。发现使用最少八个自旋适应的构型态函数，可以正确产生准分子复合物最优结构附近的 和 态的反转，这与DMRG-CASPT2计算和实验在定量上一致。讨论了与单重态和三重态中激发态能量转移相关的计算转移积分的趋势。结果表明，尽管小活性空间的选择通常依赖于系统，但MSDFT可以用作一种有效的方法，以最小活性空间（MAS）处理激发态中的分子间相互作用，用于解释结果和进行动态模拟。
