Mahato Bishwanath, Panda Aditya N
Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, India.
J Phys Chem A. 2021 Jan 14;125(1):115-125. doi: 10.1021/acs.jpca.0c08727. Epub 2020 Dec 22.
In this article, we have examined the accuracy of various density functional theory (DFT) functionals to reproduce the absorption and CD spectra of pyridine-thiophene oligomers. The performance of different levels of approximations in DFT functionals is discussed with reference to the ADC(2) results. Starting from a linear system, like monomer, calculations are carried out at ADC(2) and DFT levels till a helical system, like pentamer, is formed. For vertical excitation energies, results obtained with functionals, like CAM-B3LYP, ωB97XD, and M06-2X, are closer to the ADC(2) results. However, analysis of excited-state properties shows that the state ordering patterns or results regarding natural transition orbitals from these DFT functionals sometimes differ from the ADC(2) results. Global hybrid functionals like B3LYP and PBE0 produce excitation energies which are far away from the ADC(2) benchmark results. Similarly, pure functionals and their long-range corrected versions produce either redshifted or blueshifted energies. For the CD spectra, the above three mentioned functionals, CAM-B3LYP, ωB97XD, and M06-2X, again produce spectra closer to the benchmark spectra.
在本文中，我们研究了各种密度泛函理论（DFT）泛函在重现吡啶 - 噻吩低聚物的吸收光谱和圆二色光谱方面的准确性。参照ADC(2)结果讨论了DFT泛函中不同近似水平的性能。从线性体系（如单体）开始，在ADC(2)和DFT水平上进行计算，直至形成螺旋体系（如五聚体）。对于垂直激发能，使用诸如CAM - B3LYP、ωB97XD和M06 - 2X等泛函获得的结果更接近ADC(2)结果。然而，对激发态性质的分析表明，这些DFT泛函的态排序模式或关于自然跃迁轨道的结果有时与ADC(2)结果不同。像B3LYP和PBE0这样的全局杂化泛函产生的激发能与ADC(2)基准结果相差甚远。同样，纯泛函及其长程校正版本产生的能量要么发生红移要么发生蓝移。对于圆二色光谱，上述三种泛函，即CAM - B3LYP、ωB97XD和M06 - 2X，再次产生更接近基准光谱的光谱。
