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arXiv 1707.08054physics.chem-ph
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含时密度泛函理论中的电荷转移

Charge-Transfer in Time-Dependent Density Functional Theory

Neepa T. Maitra

摘要:

电荷转移在物理、化学和生物化学中的许多过程中起着至关重要的作用。在许多应用中,所涉及的系统的大小要求时间相关的密度泛函理论(TDDFT)被用于其计算建模,由于其前所未有的平衡精度和效率。然而,虽然准确的原则上,在实践中,近似必须作出的交换相关功能在这个理论中,和标准的功能近似表现不佳的激发具有远程电荷转移组件。激烈的进展已经取得了发展更复杂的泛函这个问题,我们审查。我们指出了一个本质的区别之间的交换相关内核需要一个准确的描述开壳层片段之间的电荷转移和闭壳层片段。然后,我们转向电荷转移动力学,这与激发问题相反,是一个高度非平衡,非微扰的过程,涉及一个完整的电子在空间中的转移。这对TDDFT泛函来说是一个更具挑战性的问题。我们描述了动态的步骤和峰值功能的确切功能随着时间的推移而演变,目前使用的泛函中缺少的。后者低估了转移的电荷量,并在电荷转移共振位置上表现出虚假的位移。我们讨论一些明确的例子。

英文摘要:

Charge transfer plays a crucial role in many processes of interest in physics, chemistry, and bio-chemistry. In many applications the size of the systems involved calls for time-dependent density functional theory (TDDFT) to be used in their computational modeling, due to its unprecedented balance between accuracy and efficiency. However, although exact in principle, in practise approximations must be made for the exchange-correlation functional in this theory, and the standard functional approximations perform poorly for excitations which have a long-range charge-transfer component. Intense progress has been made in developing more sophisticated functionals for this problem, which we review. We point out an essential difference between the properties of the exchange-correlation kernel needed for an accurate description of charge-transfer between open-shell fragments and between closed-shell fragments. We then turn to charge-transfer dynamics, which, in contrast to the excitation problem, is a highly non-equilibrium, non-perturbative, process involving a transfer of one full electron in space. This turns out to be a much more challenging problem for TDDFT functionals. We describe dynamical step and peak features in the exact functional evolving over time, that are missing in the functionals currently used. The latter underestimate the amount of charge transferred and manifest a spurious shift in the charge transfer resonance position. We discuss some explicit examples.

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