Chiba Mahito, Tsuneda Takao, Hirao Kimihiko
Department of Applied Chemistry, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan.
J Chem Phys. 2006 Apr 14;124(14):144106. doi: 10.1063/1.2186995.
An analytical excitation energy gradient of long-range corrected time-dependent density functional theory (LC-TDDFT) is presented. This is based on a previous analytical TDDFT gradient formalism, which avoids solving the coupled-perturbed Kohn-Sham equation for each nuclear degree of freedom. In LC-TDDFT, exchange interactions are evaluated by combining the short-range part of a DFT exchange functional with the long-range part of the Hartree-Fock exchange integral. This LC-TDDFT gradient was first examined by calculating the excited state geometries and adiabatic excitation energies of small typical molecules and a small protonated Schiff base. As a result, we found that long-range interactions play a significant role even in valence excited states of small systems. This analytical LC-TDDFT gradient was also applied to the investigations of small twisted intramolecular charge transfer (TICT) systems. By comparing with calculated ab initio multireference perturbation theory and experimental results, we found that LC-TDDFT gave much more accurate absorption and fluorescence energies of these systems than those of conventional TDDFTs using pure and hybrid functionals. For optimized excited state geometries, LC-TDDFT provided fairly different twisting and wagging angles of these small TICT systems in comparison with conventional TDDFT results.
提出了长程校正含时密度泛函理论（LC-TDDFT）的解析激发能梯度。这是基于先前的解析TDDFT梯度形式，它避免了为每个核自由度求解耦合微扰Kohn-Sham方程。在LC-TDDFT中，通过将DFT交换泛函的短程部分与Hartree-Fock交换积分的长程部分相结合来评估交换相互作用。首次通过计算小的典型分子和一个小的质子化席夫碱的激发态几何结构和绝热激发能来检验这种LC-TDDFT梯度。结果，我们发现长程相互作用即使在小体系的价激发态中也起着重要作用。这种解析LC-TDDFT梯度也被应用于小的扭曲分子内电荷转移（TICT）体系的研究。通过与从头算多参考微扰理论计算结果和实验结果进行比较，我们发现与使用纯泛函和杂化泛函的传统TDDFT相比，LC-TDDFT给出的这些体系的吸收和荧光能量要准确得多。对于优化的激发态几何结构，与传统TDDFT结果相比，LC-TDDFT给出的这些小TICT体系的扭曲和摆动角度有相当大的差异。
