Department of Chemistry, Stanford University, Stanford, California 94305, USA.
J Chem Phys. 2019 Oct 28;151(16):164114. doi: 10.1063/1.5125275.
Diabatic states and the couplings between them are important for quantifying, elucidating, and predicting the rates and mechanisms of many chemical and biochemical processes. Here, we propose and investigate approaches to accurately compute diabatic couplings from density functional theory (DFT) using absolutely localized molecular orbitals (ALMOs). ALMOs provide an appealing approach to generate variationally optimized diabatic states and obtain their associated forces, which allows for the relaxation of the donor and acceptor orbitals in a way that is internally consistent in how the method treats both the donor and acceptor states. Here, we show that one can obtain more accurate electronic couplings between ALMO-based diabats by employing the symmetrized transition density matrix to evaluate the exchange-correlation contribution. We demonstrate that this approach yields accurate results in comparison to other commonly used DFT-based diabatization methods across a wide array of electron and hole transfer processes occurring in systems ranging from conjugated organic molecules, such as thiophene and pentacene, to DNA base pairs. We also show that this approach yields accurate diabatic couplings even when combined with lower tiers of the DFT hierarchy, opening the door to combining it with quantum dynamics approaches to provide an ab initio treatment of nonadiabatic processes in the condensed phase.
非绝热态及其相互作用对于量化、阐明和预测许多化学和生物化学过程的速率和机制非常重要。在这里，我们提出并研究了使用完全局域分子轨道（ALMO）从密度泛函理论（DFT）准确计算非绝热耦合的方法。ALMO 提供了一种有吸引力的方法来生成变分优化的非绝热态，并获得它们相关的力，这允许以一种在处理供体和受体态时方法内部一致的方式松弛供体和受体轨道。在这里，我们表明，通过采用对称化跃迁密度矩阵来评估交换相关贡献，可以获得基于 ALMO 的非绝热之间更准确的电子耦合。我们证明，与其他常用的基于 DFT 的非绝热化方法相比，该方法在从噻吩和并五苯等共轭有机分子到 DNA 碱基对的各种电子和空穴转移过程中，都能得到准确的结果。我们还表明，即使与 DFT 层次结构的较低级别结合使用，该方法也能得到准确的非绝热耦合，为在凝聚相中将其与量子动力学方法相结合以提供非绝热过程的从头计算处理方法打开了大门。
