title: Improving anharmonic infrared spectra using semiclassically prepared molecular dynamics simulations.
abstract: Classical molecular dynamics is a convenient method for computing anharmonic infrared spectra of polyatomic molecules and condensed phase systems. However it does not perform well for predicting accurate intensities and it lacks nuclear quantization, two deficiencies that are usually accounted for by empirical scaling factors. In this paper we show on the examples of the trans isomer of nitrous acid and naphthalene that both issues can be alleviated by preparing the initial conditions according to semiclassical quantization based on a normal mode representation. The method correctly reproduces fundamental frequencies obtained with quantum mechanical methods. At increasing temperatures, the effective frequencies are found to follow the same trends as path-integral based methods. In the low-temperature limit, the band intensities predicted by the method are also found to agree with quantum mechanical considerations.
authors.affiliation: Laboratoire de Chimie Physique, UMR CNRS 8000, Université Paris Sud 11, Bât. 349, 91405 Orsay Cedex, France. van-oanh.nguyen-thi@u-psud.fr
authors.forename: Nguyen-Thi
authors.initials: NT
authors.lastname: Van-Oanh
authors.forename: Cyril
authors.initials: C
authors.lastname: Falvo
authors.forename: Florent
authors.initials: F
authors.lastname: Calvo
authors.forename: David
authors.initials: D
authors.lastname: Lauvergnat
authors.forename: Marie
authors.initials: M
authors.lastname: Basire
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Gaigeot
authors.forename: Pascal
authors.initials: P
authors.lastname: Parneix
mesh_terms: D007536:Isomerism; D056004:Molecular Dynamics Simulation; D009281:Naphthalenes / Q000737:chemistry; D009608:Nitrous Acid / Q000737:chemistry; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D013696:Temperature
chemical_list: D009281:Naphthalenes; C031721:naphthalene; D009608:Nitrous Acid