title: Theoretical Assessment of Excited State Gradients and Resonance Raman Intensities for the Azobenzene Molecule.
abstract: The ground state geometries and vibrational frequencies as well as the excitation energies and excited state gradients of the S1(nπ*) and S2(ππ*) states of trans- and cis-azobenzene are investigated by several DFT methods, namely B3LYP, PBE, M06-2X, CAM-B3LYP, and ωB97X. Excited state properties and in particular gradients are also assessed using the wave function based methods EOM-CCSD and RASPT2/RASSCF. Comparison with experimental data shows that the B3LYP functional gives the most accurate results for the ground state geometry and vibrational frequencies. The analysis of the vertical excitation energies reveals that the RASPT2 approach provides the most accurate excitation energies with deviations of the order of 0.1 eV. Among the TDDFT methods, the CAM-B3LYP functional shows the best performance on the excitation energies. By assessing the excited state gradients with respect to the reference RASPT2 data, the most accurate gradients are obtained with B3LYP, whereas other functionals as well as the EOM-CCSD and RASSCF calculations give less consistent results. Overall, despite the tendency of B3LYP to underestimate the excitation energies, this functional provides the most balanced description of both ground and excited state properties for both isomers of azobenzene in the Franck-Condon region.
authors.affiliation: Faculty of Applied Physics and Mathematics, Gdańsk University of Technology , Narutowicza 11/12, 80-233 Gdańsk, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Staniszewska
authors.affiliation: Institute of Physical Chemistry, Friedrich Schiller University Jena , Helmholtzweg 4, 07-743 Jena, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Kupfer
authors.affiliation: Faculty of Applied Physics and Mathematics, Gdańsk University of Technology , Narutowicza 11/12, 80-233 Gdańsk, Poland.
authors.forename: Marta
authors.initials: M
authors.lastname: Łabuda
authors.affiliation: Faculty of Applied Physics and Mathematics, Gdańsk University of Technology , Narutowicza 11/12, 80-233 Gdańsk, Poland.
authors.forename: Julien
authors.identifier: http://orcid.org/0000-0002-9877-6290
authors.initials: J
authors.lastname: Guthmuller
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D004583:Electrons; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D013059:Spectrum Analysis, Raman
chemical_list: D001391:Azo Compounds; C009850:azobenzene