Singlet and Triplet Exciton Transfer Integrals with FOCDFT in ADF
Part 3 of our AMS Weekly Video Series
This video demonstrates how to calculate singlet and triplet exciton transfer integrals using Fragment Orbital Constrained DFT (FOCDFT) within the Amsterdam Density Functional (ADF) program.
Exciton transfer integrals describe how excited states move between nearby molecules—key to modeling energy transport in materials through Förster and Marcus theory.
FOCDFT enables accurate construction of localized excited (diabatic) states by constraining charges or spins on molecular fragments.
The example focuses on pyrene dimers at different distances and orientations, using the CAM-B3LYP functional and a TZP all-electron basis set to ensure correct excited-state ordering and reliable coupling values.
From the results, the triplet-state electronic coupling is about 0.17 eV at a 3.5 Å separation, and the coupling strength decreases with distance. Similar methods apply to singlet states and can be extended to larger systems, such as pentacene trimers, with environmental effects included via COSMO or DRF.
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Input file and pyrene dimer structure: exciton-transfer-integrals-with-ADF.zip
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