arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2007.11569physics.chem-phcond-mat.mtrl-scicond-mat.soft
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用实时含时密度泛函理论研究离子水链中的质子转移动力学

Proton-transfer dynamics in ionized water chains using real-time Time Dependent Density Functional Theory

Vidushi Sharma, Marivi Fernández-Serra

摘要:

在光电离水基体系的密度泛函理论研究中,电荷局域化在质子转移动力学中的作用还没有得到很好的理解。这是由于在存在交换和相关函数误差的情况下提取耦合电子-核非绝热动力学的贡献的固有复杂性。在这项工作中,我们解决了这个问题,通过使用实时依赖于时间的密度泛函理论(rt-TDDFT)为基础的Escherichfest动力学模拟电离线性氢键水簇模型系统。我们的目的是了解半局域交换和相关泛函中的自相互作用误差如何影响质子转移的概率。特别是,我们表明,对于H-键合(H $_2$ O)$_n^+$链(与$n>3$),质子转移概率达到最大值,成为可比的混合泛函预测。这是因为在扩展的氢键结构中,半键合型几何形状的形成在很大程度上受到抑制。我们还展示了如何连接到质子转移反应的概率,以及电子和核电荷之间的分离的初始光空穴的本地化程度。这些结果与绝热动力学的初始波函数被允许放松的离子簇的基态,解释为什么不同的泛函和动力学方法导致定量不同的结果。

英文摘要:

In density functional-theoretic studies of photoionized water-based systems, the role of charge localization in proton-transfer dynamics is not well understood. This is due to the inherent complexity in extracting the contributions of coupled electron-nuclear non-adiabatic dynamics in the presence of exchange and correlation functional errors. In this work, we address this problem by simulating a model system of ionized linear H-bonded water clusters using real-time Time Dependent Density Functional Theory (rt-TDDFT)-based Ehrenfest dynamics. Our aim is to understand how self-interaction error in semilocal exchange and correlation functionals affects the probability of proton transfer. In particular, we show that for H-bonded (H$_2$O)$_n^+$ chains (with $n>3$), the proton-transfer probability attains a maximum, becoming comparable to that predicted by hybrid functionals. This is because the formation of hemibonded-type geometries is largely suppressed in extended H-bonded structures. We also show how the degree of localization of the initial photo-hole is connected to the probability of a proton-transfer reaction, as well as to the separation between electronic and nuclear charge. These results are compared to those obtained with adiabatic dynamics where the initial wavefunction is allowed to relax to the ground state of the ion cluster, explaining why different functionals and dynamical approaches lead to quantitatively different results.

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