title: Choosing a Functional for Computing Absorption and Fluorescence Band Shapes with TD-DFT.
abstract: The band shapes corresponding to both the absorption and emission spectra of a set of 20 representative conjugated molecules, including recently synthesized structures, have been simulated with a Time-Dependent Density Functional Theory model including diffuse atomic orbitals and accounting for bulk solvent effects. Six hybrid functionals, including two range-separated hybrids (B3LYP, PBE0, M06, M06-2X, CAM-B3LYP, and LC-PBE) have been assessed in light of the experimental band shapes obtained for these conjugated compounds. Basis set and integration grid effects have also been evaluated. It turned out that all tested functionals but LC-PBE reproduce the main experimental features for both absorption and fluorescence, though the average errors are significantly larger for the latter phenomena. No single functional stands out as the most accurate for all aspects, but B3LYP yields the smallest mean absolute deviation. On the other hand, M06-2X could be a valuable compromise for excited-states as it reproduces the 0-0 energies and also gives reasonable band shapes. The typical mean absolute deviations between the relative positions of the experimental and theoretical peaks in the vibrationally resolved spectra are ca. 100 cm(-1) for absorption and 250 cm(-1) for emission. In the same time, the relative intensities of the different maxima are reproduced by TD-DFT with a ca. 10-15% accuracy.
authors.affiliation: Laboratoire CEISAM - UMR CNR 6230, Université de Nantes , 2 Rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France.
authors.forename: Azzam
authors.initials: A
authors.lastname: Charaf-Eddin
authors.affiliation: Laboratoire CEISAM - UMR CNR 6230, Université de Nantes , 2 Rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Planchat
authors.affiliation: Department of Chemistry, University of Pisa , Via Risorgimento 35, 56126 Pisa, Italy.
authors.forename: Benedetta
authors.initials: B
authors.lastname: Mennucci
authors.affiliation: Laboratoire LECIME, CNRS UMR-7575, Chimie-ParisTech , 11 rue P. et M. Curie, F-75231 Paris Cedex 05 France.|Institut Universitaire de France , 103, bd Saint-Michel, F-75005 Paris Cedex 05, France.
authors.forename: Carlo
authors.initials: C
authors.lastname: Adamo
authors.affiliation: Laboratoire CEISAM - UMR CNR 6230, Université de Nantes , 2 Rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France.|Institut Universitaire de France , 103, bd Saint-Michel, F-75005 Paris Cedex 05, France.
authors.forename: Denis
authors.initials: D
authors.lastname: Jacquemin