A spin‐flip time‐dependent density functional tight‐binding (SF‐TDDFTB) method is developed that describes target states as spin‐flipping excitation from a high‐spin reference state obtained by the spin‐restricted open shell treatment. Furthermore, the SF‐TDDFTB formulation is extended to long‐range correction (LC), denoted as SF‐TDLCDFTB. The LC technique corrects the overdelocalization of electron density in systems such as charge‐transfer systems, which is typically found in conventional DFTB calculations as well as density functional theory calculations using pure functionals. The numerical assessment of the SF‐TDDFTB method shows smooth potential curves for the bond dissociation of hydrogen fluoride and the double‐bond rotation of ethylene and the double‐cone shape of H3 as the simplest degenerate systems. In addition, numerical assessments of SF‐TDDFTB and SF‐TDLCDFTB for 39 S0/S1 minimum energy conical intersection (MECI) structures are performed. The SF‐TDDFTB and SF‐TDLCDFTB methods drastically reduce the computational cost with accuracy for MECI structures compared with SF‐TDDFT.

中文翻译：

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时变密度泛函紧束缚方法中的自旋翻转方法：理论与应用

开发了一种自旋翻转时间相关密度泛函紧束缚（SF-TDDFTB）方法，该方法将目标状态描述为来自通过自旋受限开壳处理获得的高自旋参考状态的自旋翻转激发。此外，SF-TDDFTB 公式扩展到长程校正（LC），表示为 SF-TDLCDFTB。LC 技术纠正了电荷转移系统等系统中电子密度的过度离域，这通常出现在传统的 DFTB 计算以及使用纯泛函的密度泛函理论计算中。SF-TDDFTB 方法的数值评估表明，氟化氢的键解离和乙烯的双键旋转以及 H3 的双锥形状作为最简单的简并系统具有平滑的电位曲线。此外，对 SF-TDDFTB 和 SF-TDLCDFTB 进行了 39 个 S0/S1 最小能量圆锥相交 (MECI) 结构的数值评估。与 SF-TDDFT 相比，SF-TDDFTB 和 SF-TDLCDFTB 方法大大降低了 MECI 结构的计算成本和精度。