A very efficient and broadly applicable exciton coupling (ExC) approach based on simplified time-dependent density functional theory (sTD-DFT) is presented. Starting from this parent method, non-overlapping fragments and neglect of interfragment charge transfer excitations are assumed to arrive at the ExC procedure. This leads to an ExC Hamiltonian that pro- vides equivalent electronic absorption and circular dichroism spectra as the parent sTD-DFT method for largely separated fragments. The ExC approach easily accelerates the computa- tion of such spectra of molecular aggregates by about two orders of magnitude compared to sTD-DFT. The latter itself is already faster by about 4–5 orders of magnitude compared to regular TD-DFT. We demonstrate the performance of the approach for excitation spectra of organic molecular clusters. Given that the fragment electronic structure in the ExC-sTD- DFT approach is solved independently, computation of spectra for systems with ∼10,000 atoms can be performed within minutes of computation time. Furthermore, the role of electrostatic embedding in the independent fragments is investigated. For the purposes cov- ered in this work, the embedding can be simplified by employing a dielectric continuum, thus, greatly reducing the overall computational complexity. This approach may be used in screening photophysical properties of large molecular aggregates and soft matter materi- als. We present the derivation and implementation for the Tamm-Dancoff-approximated and the random-phase-approximation eigenvalue problems. Benchmarks compared to the parent sTD-DFT methods are shown for absorption and electronic circular dichroism spectra.

中文翻译：

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一种基于简化时变密度泛函理论的高效激子耦合方案


提出了一种基于简化时变密度泛函理论 （sTD-DFT） 的非常有效且适用广泛的激子耦合 （ExC） 方法。从这个父方法开始，假设不重叠的片段和忽略片段间电荷转移激发到达 ExC 程序。这导致了 ExC 哈密顿量，它为大部分分离的碎片提供了等效的电子吸收和圆二色光谱作为母体 sTD-DFT 方法。与 sTD-DFT 相比，ExC 方法很容易将这种分子聚集体光谱的计算速度提高约两个数量级。与常规 TD-DFT 相比，后者本身已经快了大约 4-5 个数量级。我们展示了该方法对有机分子簇激发光谱的性能。鉴于 ExC-sTD-DFT 方法中的碎片电子结构是独立求解的，因此可以在计算时间的几分钟内完成具有 ∼10,000 个原子的系统的光谱计算。此外，研究了静电嵌入在独立片段中的作用。为了实现这项工作的目的，可以通过采用介电连续体来简化嵌入，从而大大降低整体计算复杂性。这种方法可用于筛选大分子聚集体和软物质材料的光物理特性。我们介绍了 Tamm-Dancoff 近似和随机相位近似特征值问题的推导和实现。显示了与母 sTD-DFT 方法相比的吸收和电子圆二色光谱的基准。