Benchmarking singlet and triplet excitation energies of molecular semiconductors for singlet fission: Tuning the amount of HF exchange and adjusting local correlation to obtain accurate functionals for singlet-triplet gaps
Benchmarking singlet and triplet excitation energies of molecular semiconductors for singlet fission: Tuning the amount of HF exchange and adjusting local correlation to obtain accurate functionals for singlet-triplet gaps
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DOI：
10.1016/j.chemphys.2016.08.023
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发表时间：
2017-01-12
期刊：
影响因子：
2.3
通讯作者：
Engels, Bernd
中科院分区：
文献类型：
--
作者：
Brueckner, Charlotte;Engels, Bernd
用各种DFT泛函和基于波函数的方法计算的分子p型半导体的垂直和绝热单重态和三重态激发能以MS-CASPT 2/cc-pVTZ参考值为基准。一个特别的焦点在于在单重态裂变过程中非常重要的单重态-三重态能隙。单重态裂变有可能提高有机太阳能电池的器件效率，但现有的单重态裂变化合物的范围仍然有限。候选分子的计算预筛选可以扩大它，但它需要有效的方法准确预测单重态和三重态激发能。我们评估了不同的DFT公式（Tamm-Dancoff近似，线性响应依赖时间的DFT，Delta-SCF）和自旋标度方案（沿着）以及几种从头算方法（CC 2，ADC（2）/MP2，CIS（D），CIS）。虽然基于波函数的方法产生相当可靠的单重态-三重态间隙，但许多DFT泛函被证明系统地低估了三重态激发能。为了获得洞察力，精确的交换和相关性的影响详细解决。(C)2016爱思唯尔B. V.保留所有权利。
Vertical and adiabatic singlet and triplet excitation energies of molecular p-type semiconductors calculated with various DFT functionals and wave-function based approaches are benchmarked against MS-CASPT2/cc-pVTZ reference values. A special focus lies on the singlet-triplet gaps that are very important in the process of singlet fission. Singlet fission has the potential to boost device efficiencies of organic solar cells, but the scope of existing singlet-fission compounds is still limited. A computational prescreening of candidate molecules could enlarge it; yet it requires efficient methods accurately predicting singlet and triplet excitation energies. Different DFT formulations (Tamm-Dancoff approximation, linear response time-dependent DFT, Delta-SCF) and spin scaling schemes along with several ab initio methods (CC2, ADC(2)/MP2, CIS(D), CIS) are evaluated. While wave-function based methods yield rather reliable singlet-triplet gaps, many DFT functionals are shown to systematically underestimate triplet excitation energies. To gain insight, the impact of exact exchange and correlation is in detail addressed. (C) 2016 Elsevier B.V. All rights reserved.