Analysis Technology Development Center, Canon Inc., 30-2, Shimomaruko 3-chome, Tokyo 146-8501, Japan.
J Chem Phys. 2012 Feb 14;136(6):064109. doi: 10.1063/1.3684233.
A new method for analyzing and visualizing the molecular excited states, named "excited state paired interacting orbital (EPIO)," is proposed. The method is based both on the paired interacting orbital (PIO) proposed by Fujimoto and Fukui [J. Chem. Phys. 60, 572 (1974)] and the natural transition orbital (NTO) by Martin [J. Chem. Phys. 118, 4775 (2003)]. Within the PIO method, orbital interactions between the two fragmented molecules are represented practically only by a few pairs of fragment orbitals. The NTO method is a means of finding a compact orbital representation for the electronic transitions in the excited states. With the method, electronic transitions are expressed by a few particle-hole orbital pairs and a clear picture on the electronic transitions is obtained. EPIO method is designed to have both properties of the preceding two methods: electronic transitions in composite molecular systems can be expressed with a few pairs of EPIOs which are constructed with fragmented molecular orbitals (MOs). Excited state characters, such as charge transfer and local excitations, are analyzed by using EPIOs with their generation probabilities. Thus, the present method gives us clear information on the composition of MOs which play an important role in the molecular excitation processes, e.g., optical processes.
提出了一种新的分析和可视化分子激发态的方法，称为“激发态配对相互作用轨道（EPIO）”。该方法基于 Fujimoto 和 Fukui [J. Chem. Phys. 60, 572 (1974)] 提出的配对相互作用轨道（PIO）和 Martin [J. Chem. Phys. 118, 4775 (2003)] 的自然跃迁轨道（NTO）。在 PIO 方法中，两个碎片化分子之间的轨道相互作用实际上仅由少数几对碎片轨道表示。NTO 方法是寻找激发态电子跃迁的紧凑轨道表示的一种手段。通过该方法，可以用少数几个粒子-空穴轨道对来表示电子跃迁，并获得电子跃迁的清晰图像。EPIO 方法旨在同时具有前两种方法的性质：可以用由碎片化分子轨道（MO）构建的少数对 EPIOs 来表示复合分子系统中的电子跃迁。通过使用具有生成概率的 EPIOs 来分析激发态特性，例如电荷转移和局部激发。因此，该方法为我们提供了有关在分子激发过程中起重要作用的 MO 组成的清晰信息，例如光学过程。
