Chemistry and Chemical Biology, School of Natural Sciences, University of California, Merced, 5200 North Lake Road, Merced, California 95343, United States.
J Phys Chem A. 2013 Feb 7;117(5):947-52. doi: 10.1021/jp3084309. Epub 2013 Jan 25.
Conventional density-functional theory (DFT) has the potential to overbind radical-molecule complexes because of erroneous charge transfer. We examined this behavior by exploring the ability of various DFT approximations to predict fractional charge transfer and by quantifying the overbinding in a series of complexes. It is demonstrated that too much charge is transferred from molecules to radicals when the radical singly unoccupied molecular orbitals are predicted to be erroneously too low in energy relative to the molecule highest occupied molecular orbitals, leading to excessive Coulombic attraction. In this respect, DFT methods formulated with little or no Hartree-Fock exchange perform most poorly. The present results illustrate that the charge-transfer problem is much broader than may have been previously expected and is not limited to conventional (i.e., molecule-molecule) donor-acceptor complexes.
传统密度泛函理论（DFT）由于错误的电荷转移，有可能过度束缚自由基-分子复合物。我们通过研究各种 DFT 近似方法预测分数电荷转移的能力，并通过量化一系列复合物中的过键合来检验这种行为。结果表明，当自由基单占据分子轨道相对于分子最高占据分子轨道被错误地预测为能量过低时，从分子向自由基转移的电荷过多，导致过多的库仑吸引力。在这方面，用很少或没有 Hartree-Fock 交换构建的 DFT 方法表现最差。目前的结果表明，电荷转移问题比以前预期的要广泛得多，并且不仅限于传统的（即分子-分子）给体-受体复合物。
