Local-Mode Approach to Modeling Multidimensional Infrared Spectra of Metal Carbonyls

Title Local-Mode Approach to Modeling Multidimensional Infrared Spectra of Metal Carbonyls
Publication Type Journal Article
Year of Publication 2011
Authors Baiz CR, Kubarych KJ, Geva E, Sibert, Edwin L. III
Journal Journal of Physical Chemistry A
Volume 115
Pagination 5354-5363
Date Published Jun
Accession Number ISI:000290914500014
Keywords 2d-ir, ab-initio, approximation, Chemistry, Physical, correlation-energy, density, dynamics, ir, liquid h2o, Physics, Atomic, Molecular & Chemical, spectroscopy, Vibrational spectroscopy, water
Abstract We present a general approach for modeling multidimensional infrared spectra based on a combination of phenomenological fitting and ab initio electronic structure calculations. The vibrational Hamiltonian is written in terms of bilinearly coupled Morse oscillators that represent local carbonyl stretches. This should be contrasted with the previous approach, where the anharmonic Hamiltonian was given in terms of normal-mode coordinates (Baiz et al. J. Phys. Chem. A 2009, 113, 9617). The bilinearly coupled Morse oscillator Hamiltonian is parametrized such that the frequencies and couplings are consistent with experiment, and the anharmonicities are computed by density functional theory. The advantages of the local-mode versus normal-mode approaches are discussed, as well as the ability of different density functionals to provide accurate estimates of the model parameters. The applicability and usefulness of the new approach are demonstrated in the context of the recently measured multidimensional infrared spectra of dimanganese decacarbonyl. The shifts in local site frequencies, couplings, and anharmonicities due to hydrogen bonding to the individual carbonyls are explored. It is found that, even though the effect of hydrogen bonding is nonlocal, it is additive.
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