Isborn Christine M, Li Xiaosong
Department of Chemistry, University of Washington, Seattle, Washington 98195-1700.
J Chem Theory Comput. 2009 Sep 8;5(9):2415-9. doi: 10.1021/ct900264b. Epub 2009 Aug 12.
Real-time time-dependent Hartree-Fock (TDHF)/density functional theory (TDDFT) has been gaining in popularity because of its ability to treat phenomena beyond the linear response and because it has the potential to be more computationally powerful than frequency domain TDHF/TDDFT. Within real-time TDHF/TDDFT, we present a method that gives the excited state triplet energies starting from a singlet ground state. Using a spin-dependent field, we break the spin-symmetry of the α and β density matrices, which incorporates a triplet contribution into the superposition state. The α electron density follows the applied field, and the β electron density responds to the perturbation from the changing α electron density. We examine the individual α/β responses during the electron density propagation. Singlet-triplet transitions appear as 'dark' states: they are present in the α/β responses but are absent from the total electron density response.
实时含时哈特里-福克（TDHF）/密度泛函理论（TDDFT）因其能够处理超出线性响应的现象，且有可能比频域TDHF/TDDFT具有更强的计算能力，而越来越受到欢迎。在实时TDHF/TDDFT框架内，我们提出了一种从单重态基态出发计算激发态三重态能量的方法。通过使用自旋相关场，我们打破了α和β密度矩阵的自旋对称性，这将三重态贡献纳入了叠加态。α电子密度跟随外加场，而β电子密度则响应来自变化的α电子密度的微扰。我们研究了电子密度传播过程中α/β的个体响应。单重态-三重态跃迁表现为“暗”态：它们存在于α/β响应中，但在总电子密度响应中不存在。
