title: Accurate Simulation of Resonance-Raman Spectra of Flexible Molecules: An Internal Coordinates Approach.
abstract: The interpretation and analysis of experimental resonance-Raman (RR) spectra can be significantly facilitated by vibronic computations based on reliable quantum-mechanical (QM) methods. With the aim of improving the description of large and flexible molecules, our recent time-dependent formulation to compute vibrationally resolved electronic spectra, based on Cartesian coordinates, has been extended to support internal coordinates. A set of nonredundant delocalized coordinates is automatically generated from the molecular connectivity thanks to a new general and robust procedure. In order to validate our implementation, a series of molecules has been used as test cases. Among them, rigid systems show that normal modes based on Cartesian and delocalized internal coordinates provide equivalent results, but the latter set is much more convenient and reliable for systems characterized by strong geometric deformations associated with the electronic transition. The so-called Z-matrix internal coordinates, which perform well for chain molecules, are also shown to be poorly suited in the presence of cycles or nonstandard structures.
authors.affiliation: Scuola Normale Superiore , Piazza dei Cavalieri 7, I-56126 Pisa, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Baiardi
authors.affiliation: Scuola Normale Superiore , Piazza dei Cavalieri 7, I-56126 Pisa, Italy.|Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti OrganoMetallici (ICCOM-CNR), UOS di Pisa, Area della Ricerca CNR , Via G. Moruzzi 1, I-56124 Pisa, Italy.
authors.forename: Julien
authors.initials: J
authors.lastname: Bloino
authors.affiliation: Scuola Normale Superiore , Piazza dei Cavalieri 7, I-56126 Pisa, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Barone
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D008968:Molecular Conformation; D011789:Quantum Theory; D012428:Ruthenium; D013059:Spectrum Analysis, Raman; D014498:Uracil / Q000031:analogs & derivatives / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D007093:Imidazoles; D014498:Uracil; C029899:imidazole; D012428:Ruthenium