Effect of Hartree-Fock exact exchange on intramolecular magnetic coupling constants of organic diradicals
Effect of Hartree-Fock exact exchange on intramolecular magnetic coupling constants of organic diradicals
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DOI：
10.1063/1.4905561
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发表时间：
2015-01-14
影响因子：
4.4
通讯作者：
Lee, Jin Yong
中科院分区：
文献类型：
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作者：
Cho, Daeheum;Ko, Kyoung Chul;Lee, Jin Yong
计算了五元或六元芳环连接的双自由基体系的分子内磁耦合常数(J)，得到了不同密度泛函(DFT)泛函的标度因子(实验J/计算J比)。A组(PBE、TPSSh、B3LYP、B97-1、X3LYP、PBE0和BH&HLYP)和B组(M06-L、M06、M06-2X和M06-HF)的标度因子随着Hartree-Fock精确交换量的增加而减小，也就是说，对计算J的高估变得更加严重。通过比较含有不同含量的HFX的B3LYP类似物，进一步研究了DFT官能团的HFX部分对J值、自旋污染和自旋密度分布的影响。结果表明，每个原子的自旋污染和自旋密度都随着HFX的增加而增加。最重要的是，新开发的含5%HFX的BLYP5泛函具有1.029的标度因子，表明在没有标度的情况下，计算的J值与实验值非常接近。BLYP-5可用于精确计算五元或六元芳环偶联剂连接的双自由基分子内磁性耦合常数(J)。(C)2015 AIP出版有限责任公司。
The intramolecular magnetic coupling constant (J) of diradical systems linked with five- or six-membered aromatic rings was calculated to obtain the scaling factor (experimental J/calculated J ratio) for various density functional theory (DFT) functionals. Scaling factors of group A (PBE, TPSSh, B3LYP, B97-1, X3LYP, PBE0, and BH&HLYP) and B (M06-L, M06, M06-2X, and M06-HF) were shown to decrease as the amount of Hartree-Fock exact exchange (HFx) increases, in other words, overestimation of calculated J becomes more severe as the HFx increases. We further investigated the effect of HFx fraction of DFT functional on J value, spin contamination, and spin density distributions by comparing the B3LYP analogues containing different amount of HFx. It was revealed that spin contamination and spin densities at each atom increases as the HFx increases. Above all, newly developed BLYP-5 functional, which has 5% of HFx, was found to have the scaling factor of 1.029, indicating that calculated J values are very close to that of experimental values without scaling. BLYP-5 has potential to be utilized for accurate evaluation of intramolecular magnetic coupling constant (J) of diradicals linked by five-or six-membered aromatic ring couplers. (C) 2015 AIP Publishing LLC.