Electronic couplings for molecular charge transfer: Benchmarking CDFT, FODFT, and FODFTB against high-level ab initio calculations
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)
- Institute of Physical Chemistry, Karlsruhe Institute of Technology, Fritz-Haber-Weg 6, 76131 Karlsruhe (Germany)
- Department of Chemistry, Technical University of Munich, Lichtenbergstr. 4, 85747 Garching (Germany)
We introduce a database (HAB11) of electronic coupling matrix elements (H{sub ab}) for electron transfer in 11 π-conjugated organic homo-dimer cations. High-level ab inito calculations at the multireference configuration interaction MRCI+Q level of theory, n-electron valence state perturbation theory NEVPT2, and (spin-component scaled) approximate coupled cluster model (SCS)-CC2 are reported for this database to assess the performance of three DFT methods of decreasing computational cost, including constrained density functional theory (CDFT), fragment-orbital DFT (FODFT), and self-consistent charge density functional tight-binding (FODFTB). We find that the CDFT approach in combination with a modified PBE functional containing 50% Hartree-Fock exchange gives best results for absolute H{sub ab} values (mean relative unsigned error = 5.3%) and exponential distance decay constants β (4.3%). CDFT in combination with pure PBE overestimates couplings by 38.7% due to a too diffuse excess charge distribution, whereas the economic FODFT and highly cost-effective FODFTB methods underestimate couplings by 37.6% and 42.4%, respectively, due to neglect of interaction between donor and acceptor. The errors are systematic, however, and can be significantly reduced by applying a uniform scaling factor for each method. Applications to dimers outside the database, specifically rotated thiophene dimers and larger acenes up to pentacene, suggests that the same scaling procedure significantly improves the FODFT and FODFTB results for larger π-conjugated systems relevant to organic semiconductors and DNA.
- OSTI ID:
- 22253447
- Journal Information:
- Journal of Chemical Physics, Vol. 140, Issue 10; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CATIONS
CHARGE DENSITY
CHARGE DISTRIBUTION
CLUSTER MODEL
COUPLINGS
DENSITY FUNCTIONAL METHOD
DIMERS
DNA
ELECTRON TRANSFER
HARTREE-FOCK METHOD
INTERACTIONS
MATRIX ELEMENTS
ORGANIC SEMICONDUCTORS
PENTACENE
PERTURBATION THEORY
POLYCYCLIC SULFUR HETEROCYCLES
SCALING
THIOPHENE