基于跃迁的约束DFT方法在超分子体系激发态稳健可靠处理中的应用
Transition-Based Constrained DFT for the Robust and Reliable Treatment of Excitations in Supramolecular Systems
摘要：
尽管有各种可用的计算方法，用于计算激发能的最先进的方法，如时间相关的密度泛函理论（TDDFT），是计算上的要求，并因此限于适度的系统大小。在这里，我们介绍了一种新的变化约束DFT（CDFT），其中的约束对应于一个特定的过渡（T），或过渡的组合，占用和虚拟轨道之间，而不是在传统的CDFT的模拟空间的区域。我们比较了T-CDFT与TDDFT和$Δ$ SCF结果的低激发态（S $_{1}$和T $_{1}$）的一组气相并苯分子和OLED发射器，以及从文献中的参考结果。在PBE理论水平上，T-CDFT对两类分子的性能都优于$Δ$ SCF，同时也证明更稳健。对于在并苯中看到的局部激发，T-CDFT和TDDFT表现得同样好。对于在OLED分子中看到的电荷转移（CT）样激发，T-CDFT也表现良好，与TDDFT看到的严重能量低估相反。换句话说，T-CDFT同样适用于局部激发和CT状态，以比TDDFT低得多的计算成本提供更可靠的激发能。T-CDFT是为大型系统设计的，并已在线性缩放BigDFT代码中实现。因此，它非常适合探索显式环境对激发能的影响，为未来模拟复杂现实形态中的激发态铺平了道路，例如OLED材料中发生的那些。
英文摘要：
Despite the variety of available computational approaches, state-of-the-art methods for calculating excitation energies such as time-dependent density functional theory (TDDFT), are computationally demanding and thus limited to moderate system sizes. Here, we introduce a new variation of constrained DFT (CDFT), wherein the constraint corresponds to a particular transition (T), or combination of transitions, between occupied and virtual orbitals, rather than a region of the simulation space as in traditional CDFT. We compare T-CDFT with TDDFT and $Δ$SCF results for the low lying excited states (S$_{1}$ and T$_{1}$) of a set of gas phase acene molecules and OLED emitters, as well as with reference results from the literature. At the PBE level of theory, T-CDFT outperforms $Δ$SCF for both classes of molecules, while also proving to be more robust. For the local excitations seen in the acenes, T-CDFT and TDDFT perform equally well. For the charge-transfer (CT)-like excitations seen in the OLED molecules, T-CDFT also performs well, in contrast to the severe energy underestimation seen with TDDFT. In other words, T-CDFT is equally applicable to both local excitations and CT states, providing more reliable excitation energies at a much lower computational cost than TDDFT. T-CDFT is designed for large systems and has been implemented in the linear scaling BigDFT code. It is therefore ideally suited for exploring the effects of explicit environments on excitation energies, paving the way for future simulations of excited states in complex realistic morphologies, such as those which occur in OLED materials.
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