title: Basis set and electron correlation effects on initial convergence for vibrational nonlinear optical properties of conjugated organic molecules.
abstract: Using three typical pi-conjugated molecules (1,3,5-hexatriene, 1-formyl-6-hydroxyhexa-1,3,5- triene, and 1,1-diamino-6,6-dinitrohexa-1,3,5-triene) we investigate the level of ab initio theory necessary to produce reliable values for linear and nonlinear optical properties, with emphasis on the vibrational contributions that are known to be important or potentially important. These calculations are made feasible by employing field-induced coordinates in combination with a finite field procedure. For many, but not all, purposes the MP2/6-31+G(d) level is adequate. Based on our results the convergence of the usual perturbation treatment for vibrational anharmonicity was examined. Although this treatment is initially convergent in most circumstances, a problematic situation has been identified.
authors.affiliation: Institute of Computational Chemistry and Department of Chemistry, University of Girona, Campus de Montilivi, 17071 Girona, Catalonia, Spain.
authors.forename: Miquel
authors.initials: M
authors.lastname: Torrent-Sucarrat
authors.forename: Miquel
authors.initials: M
authors.lastname: Solà
authors.forename: Miquel
authors.initials: M
authors.lastname: Duran
authors.forename: Josep M
authors.initials: JM
authors.lastname: Luis
authors.forename: Bernard
authors.initials: B
authors.lastname: Kirtman
mesh_terms: D004583:Electrons; D017711:Nonlinear Dynamics; D055095:Optics and Photonics; D009930:Organic Chemicals / Q000737:chemistry*; D011090:Polyenes / Q000737:chemistry*; D013057:Spectrum Analysis; D014732:Vibration
chemical_list: C512192:1,1-diamino-6,6-dinitrohexa-1,3,5-triene; C512193:1-formyl-6-hydroxyhexa-1,3,5- triene; D009930:Organic Chemicals; D011090:Polyenes; C512191:1,3,5-hexatriene