Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing, People's Republic of China.
J Chem Phys. 2011 Apr 7;134(13):134101. doi: 10.1063/1.3573374.
The excited states of open-shell systems calculated by unrestricted Kohn-Sham-based time-dependent density functional theory (U-TD-DFT) are often heavily spin-contaminated and hence meaningless. This is solved ultimately by the recently proposed spin-adapted time-dependent density functional theory (TD-DFT) (S-TD-DFT) [J. Chem. Phys. 133, 064106 (2010)]. Unlike the standard restricted open-shell Kohn-Sham-based TD-DFT (R-TD-DFT) which can only access the singlet-coupled single excitations, the S-TD-DFT can capture both the singlet- and triplet-coupled single excitations with the same computational effort as the U-TD-DFT. The performances of the three approaches (U-TD-DFT, R-TD-DFT, and S-TD-DFT) are compared for both the spin-conserving and spin-flip excitations of prototypical open-shell systems, the nitrogen (N(2)(+)) and naphthalene (C(10)H(8)(+)) cations. The results show that the S-TD-DFT gives rise to balanced descriptions of excited states of open-shell systems.
基于非限制 Kohn-Sham 时变密度泛函理论 (U-TD-DFT) 计算的开壳层体系的激发态常常受到严重的自旋污染，因此毫无意义。这一问题最终通过最近提出的自旋自适应时变密度泛函理论 (TD-DFT) (S-TD-DFT) [J. Chem. Phys. 133, 064106 (2010)] 得到解决。与只能访问单重态耦合单激发的标准受限开壳层 Kohn-Sham 基 TD-DFT (R-TD-DFT) 不同，S-TD-DFT 可以用与 U-TD-DFT 相同的计算工作量捕获单重态和三重态耦合的单激发。比较了三种方法 (U-TD-DFT、R-TD-DFT 和 S-TD-DFT) 在典型开壳层体系氮 (N(2)(+)) 和萘 (C(10)H(8)(+)) 阳离子的自旋守恒和自旋翻转激发中的性能。结果表明，S-TD-DFT 导致了对开壳层体系激发态的平衡描述。
