Hapka Michał, Pernal Katarzyna, Gritsenko Oleg V
Institute of Physics, Lodz University of Technology, PL-90-924 Lodz, Poland.
Faculty of Chemistry, University of Warsaw, 02-093 Warsaw, Poland.
J Phys Chem Lett. 2020 Aug 6;11(15):5883-5889. doi: 10.1021/acs.jpclett.0c01616. Epub 2020 Jul 13.
We discuss the interplay between the nondynamic and dynamic electron correlation in excited states from the perspective of the suppression of dynamic correlation (SDC) and enhancement of dynamic correlation (EDC) effects. We reveal that there exists a connection between the ionic character of a wave function and EDC. Following this finding we introduce a quantitative measure of ionicity based solely on local functions without referring to valence bond models. The ability to recognize both the SDC and EDC regions underlies the presented method, named CASΠDFT, combining complete active space (CAS) wave function and density functional theory (DFT) via the on-top pair density (Π) function. We extend this approach to excited states by devising an improved representation of the EDC effect in the correlation functional. The generalized CASΠDFT uses different DFT functionals for ground and excited states. Numerical demonstration for singlet π → π* excitations shows that CASΠDFT offers satisfactory accuracy at a fraction of the cost of the approaches.
我们从抑制动态关联（SDC）和增强动态关联（EDC）效应的角度讨论激发态中非动态和动态电子关联之间的相互作用。我们揭示了波函数的离子特性与EDC之间存在联系。基于这一发现，我们引入了一种仅基于局部函数的离子性定量度量，而无需参考价键模型。识别SDC和EDC区域的能力是所提出的名为CASΠDFT的方法的基础，该方法通过顶对密度（Π）函数将完全活性空间（CAS）波函数与密度泛函理论（DFT）相结合。我们通过在相关泛函中设计EDC效应的改进表示，将这种方法扩展到激发态。广义CASΠDFT对基态和激发态使用不同的DFT泛函。单重态π→π*激发的数值演示表明，CASΠDFT以一小部分方法的成本提供了令人满意的精度。
