title: Improved Infrared Spectra Prediction by DFT from a New Experimental Database.
abstract: This work aims to improve the computation of infrared spectra of gas-phase cations using DFT methods. Experimental infrared multiple photon dissociation (IRMPD) spectra for ten Zn and Ru organometallic complexes have been used to provide reference data for 64 vibrational modes in the 900-2000 cm-1range. The accuracy of the IR vibrational frequencies predicted for these bands has been assessed over five DFT functionals and three basis sets. The functionals include the popular B3LYP and M06-2X hybrids and the range-separated hybrids (RSH) CAM-B3LYP, LC-BLYP, and ωB97X-D. B3LYP gives the best mean absolute error (MAE) and root-mean-square error (RMSE) values of 7.1 and 9.6 cm-1, whilst the best RSH functional, ωB97X-D, gives 12.8 and 16.6 cm-1, respectively. Using linear correlations instead of scaling factors improves the prediction accuracy significantly for all functionals. Experimental and computed spectra for a single complex can show significant differences even when the molecular structure is calculated correctly, and a means of defining confidence limits for any given computed structure is also provided.
authors.affiliation: LCM, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128, Palaiseau, France.
authors.forename: Madanakrishna
authors.initials: M
authors.lastname: Katari
authors.affiliation: LCM, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128, Palaiseau, France.
authors.forename: Edith
authors.initials: E
authors.lastname: Nicol
authors.affiliation: Laboratoire de Chimie Physique, Université Paris Sud, CNRS, 91405, Orsay, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Steinmetz
authors.affiliation: Laboratoire de Chimie Physique, Université Paris Sud, CNRS, 91405, Orsay, France.
authors.forename: Guillaume
authors.identifier: http://orcid.org/0000-0002-1176-620X
authors.initials: G
authors.lastname: van der Rest
authors.affiliation: LCM, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128, Palaiseau, France.
authors.forename: Duncan
authors.initials: D
authors.lastname: Carmichael
authors.affiliation: LCM, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128, Palaiseau, France.
authors.forename: Gilles
authors.identifier: http://orcid.org/0000-0002-5677-3569
authors.initials: G
authors.lastname: Frison
keywords: density functional calculations; dft benchmark; ir spectroscopy; mass spectrometry; organometallic complexes