skip to main content

SciTech ConnectSciTech Connect

Title: Electronic couplings for molecular charge transfer: Benchmarking CDFT, FODFT, and FODFTB against high-level ab initio calculations

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 themore » same scaling procedure significantly improves the FODFT and FODFTB results for larger π-conjugated systems relevant to organic semiconductors and DNA.« less
Authors:
;  [1] ;  [1] ;  [2] ; ;  [3] ;  [4]
  1. Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)
  2. (Germany)
  3. Institute of Physical Chemistry, Karlsruhe Institute of Technology, Fritz-Haber-Weg 6, 76131 Karlsruhe (Germany)
  4. Department of Chemistry, Technical University of Munich, Lichtenbergstr. 4, 85747 Garching (Germany)
Publication Date:
OSTI Identifier:
22253447
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 10; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; 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