title: Vibrational computations beyond the harmonic approximation: performances of the B3LYP density functional for semirigid molecules.
abstract: The performances of the B3LYP density functional in the computation of harmonic and anharmonic frequencies were tested using 14 standard basis sets of double and triple zeta quality for a set of semirigid molecules containing from 4 to 12 atoms. The quality of the results is assessed by comparison with the most reliable computations available in the literature. The study reveals that the relatively cheap 6-31+G(d,p) basis set performs a very good job for harmonic frequency calculations and that B3LYP anharmonicities are in close agreement with the reference values irrespective of the basis set used. On these grounds "hybrid force fields" are proposed to achieve the best compromise between computer time and quality of the results.
authors.affiliation: Dipartimento di Chimica, Università Federico II, Complesso Universitario Monte Sant'Angelo, Via Cintia, I-80126 Napoli, Italy.
authors.forename: Philippe
authors.initials: P
authors.lastname: Carbonniere
authors.forename: Tecla
authors.initials: T
authors.lastname: Lucca
authors.forename: Claude
authors.initials: C
authors.lastname: Pouchan
authors.forename: Nadia
authors.initials: N
authors.lastname: Rega
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Barone