Calculation of Charge-Transfer Electronic Coupling with Nonempirically Tuned Range-Separated Density Functional

Computation of charge-transfer coupling energy with a nonempirically tuned range-separated density functional is examined. The results are assessed by comparing with the high-level ab initio benchmark data sets, HAB11 (Kubas J. Chem. Phys. 2014, 140, 104105) of 11 cation radical homodimers and HAB7– (Kubas Phys. Chem. Chem. Phys. 2015, 17, 14342) of 7 anion radical homodimers. The mean relative unsigned errors (MRUEs) of the charge-transfer coupling energy were 3.2% for the HAB11 set and 7.3% for the HAB7– set. The MRUEs of the exponential decay constant along the face-to-face intermolecular distance were 2.2% for the HAB11 set and 4.9% for the HAB7– set. The errors were always smaller than those from the popular B3LYP functional and, in most cases, smaller than those reported in previous studies. We also found nearly linear correlations between the tuned range-separated parameter μ and the energies of highest occupied and lowest unoccupied orbitals of the monomers and between 1/μ and the number of double bonds in the monomers