title: Carotenoids and light-harvesting: from DFT/MRCI to the Tamm-Dancoff approximation.
abstract: Carotenoids are known to play a fundamental role in photosynthetic light-harvesting (LH) complexes; however, an accurate quantum-mechanical description of that is still missing. This is due to the multideterminant nature of the involved electronic states combined with an extended conjugation which limits the applicability of many of the most advanced approaches. In this study, we apply a multireference configuration interaction extension of density functional theory (DFT/MRCI) to describe transition energies and densities as well as the corresponding excitonic couplings, for the three lowest singlet excited states of nine carotenoids present in three different LH complexes of algae and plants. These benchmark results are used to find an approximated computational approach, which could be used to quantitatively reproduce the key quantities at a reduced computational cost. To this end, we tested the Tamm-Dancoff approximation (TDA) to time-dependent density functional theory in combination with different functionals. By analyzing the errors with respect to DFT/MRCI-TDA results for the full set of electronic properties, we conclude that TDA-TPSS with small basis sets indeed represents an effective approach to investigate LH processes that involve carotenoids.
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, University of Pisa , Via G. Moruzzi, 56124 Pisa, Italy.
authors.forename: Oliviero
authors.initials: O
authors.lastname: Andreussi
authors.affiliation: Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Knecht
authors.affiliation: Institute of Theoretical and Computational Chemistry, University of Düsseldorf , Universitaẗsstraße 1,40225 Düsseldorf, Germany.
authors.forename: Christel M
authors.initials: CM
authors.lastname: Marian
authors.affiliation: Department of Physics, Chemistry and Pharmacy, University of Southern Denmark , Campusvej 55, 5230 Odense M, Denmark.
authors.forename: Jacob
authors.initials: J
authors.lastname: Kongsted
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, University of Pisa , Via G. Moruzzi, 56124 Pisa, Italy.
authors.forename: Benedetta
authors.initials: B
authors.lastname: Mennucci
mesh_terms: D002338:Carotenoids / Q000737:chemistry* / Q000378:metabolism; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D015394:Molecular Structure; D011789:Quantum Theory
chemical_list: D045342:Light-Harvesting Protein Complexes; D002338:Carotenoids