title: Failure of time-dependent density functional theory for long-range charge-transfer excited states: the zincbacteriochlorin-bacteriochlorin and bacteriochlorophyll-spheroidene complexes.
abstract: It is well-known that time-dependent density functional theory (TDDFT) yields substantial errors for the excitation energies of charge-transfer (CT) excited states, when approximate standard exchange-correlation (xc) functionals are used, for example, SVWN, BLYP, or B3LYP. Also, the correct 1/R asymptotic behavior of CT states with respect to a distance coordinate R between the separated charges of the CT state is not reproduced by TDDFT employing these xc-functionals. Here, we demonstrate by analysis of the TDDFT equations that the first failure is due to the self-interaction error in the orbital energies from the ground-state DFT calculation, while the latter is a similar self-interaction error in TDDFT arising through the electron transfer in the CT state. Possible correction schemes, such as inclusion of exact Hartree-Fock or exact Kohn-Sham exchange, as well as aspects of the exact xc-functional are discussed in this context. Furthermore, a practical approach is proposed which combines the benefits of TDDFT and configuration interaction singles (CIS) and which does not suffer from electron-transfer self-interaction. The latter approach is applied to a (1,4)-phenylene-linked zincbacteriochlorin-bacteriochlorin complex and to a bacteriochlorophyll-spheroidene complex, in which CT states may play important roles in energy and electron-transfer processes. The errors of TDDFT alone for the CT states are demonstrated, and reasonable estimates for the true excitation energies of these states are given.
authors.affiliation: Institut für Physikalische und Theoretische Chemie, Johann Wolfgang Goethe-Universität Frankfurt, Marie-Curie-Strasse 11, 60439 Frankfurt, Germany. andreas.dreuw@theochem.uni-frankfurt.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Dreuw
authors.forename: Martin
authors.initials: M
authors.lastname: Head-Gordon
mesh_terms: D001429:Bacteriochlorophylls / Q000737:chemistry*; D002338:Carotenoids / Q000737:chemistry*; D004579:Electron Transport; D004735:Energy Transfer; D008665:Metalloporphyrins / Q000737:chemistry*; D008956:Models, Chemical; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D020560:Proteobacteria / Q000378:metabolism; D013598:Systems Theory; D013997:Time Factors
chemical_list: D001429:Bacteriochlorophylls; D008665:Metalloporphyrins; D045322:Photosynthetic Reaction Center Complex Proteins; D011166:Porphyrins; C452433:bacteriochlorin; C005637:spheroidene; C017802:zinc hematoporphyrin; D002338:Carotenoids