Singlet–triplet energy gaps (ΔE_ST) for multiresonant molecular systems are investigated within time-dependent density functional theory (TDDFT), using conventional linear response TDDFT (LR-TDDFT) and double hybrid TDDFT (DH-TDDFT) schemes. LR-TDDFT methods systematically overestimate ΔE_ST; on the other hand, by explicitly taking double excitation characters into consideration, DH-TDDFT considerably improves the gap problem. Further theoretical analysis shows that DH-TDDFT calculations also work for the description of negative gap situations, which LR-TDDFT intrinsically fails. The present findings demonstrate the applicability of TDDFT-based methods for predicting ΔE_ST as a relatively low-cost computational approach, encouraging us to develop new exchange-correlation functionals suited for DH-TDDFT calculations.

使用传统的线性响应 TDDFT (LR-TDDFT) 和双混合 TDDFT (DH-TDDFT) 方案，在时间相关密度泛函理论 (TDDFT) 内研究了多共振分子系统的单重态-三重态能隙 (Δ E _{ST )。}LR-TDDFT 方法系统地高估了 Δ E _ST；另一方面，通过明确考虑双激励特性，DH-TDDFT 显着改善了间隙问题。进一步的理论分析表明，DH-TDDFT 计算也适用于描述负间隙情况，而 LR-TDDFT 本质上是失败的。目前的研究结果证明了基于 TDDFT 的方法预测 Δ E _{ST的适用性}作为一种相对低成本的计算方法，鼓励我们开发适合 DH-TDDFT 计算的新交换相关函数。