CODECS 2013 Workshop. San Lorenzo de El Escorial, Madrid, 18th –22nd April, 2013
Computational study of vibrational spectra of some water containing
complexes of atmospheric interest and of some small molecules
adsorbed on catalytic metal surface
Elina Sälli a, Teemu Salmi a, Lauri Halonena
a
Laboratory of Physical Chemistry, Department of Chemistry, PO Box 55 (A.I. Virtasen aukio 1),
FIN-00014 University of Helsinki, Finland
lauri.halonen@helsinki.fi
Water and some of its complexes are greenhouse gases in Earth’s atmosphere. Stretching
vibrational overtone spectroscopy in the near-infrared region is interesting for the experimental
observation of these species under atmospheric conditions. Consequently, we have computed
high-frequency stretching and bending vibrational overtone spectra of water [1 - 3] and water
ammonia complexes [4]. We have extended the gas-phase vibrational models to water [5] and
ammonia [6, 7] adsorbed on metal surfaces.
The water and water ammonia complexes have been approximated as individually vibrating
monomer units. Internal coordinate Hamiltonians are constructed for each monomer unit using
exact kinetic energy operators within the Born-Oppenheimer approximation. The potential
energy surfaces are calculated using the coupled cluster method with correlation consistent basis
sets. The explicitly correlated F12 theory, which includes the interelectronic coordinate in the
electronic wavefunction, has been adopted together with the coupled cluster method for the water
ammonia complex. The dipole moment surfaces are obtained with the finite difference method.
Eigenvalues of the Hamiltonians are computed variationally. Eigenvectors with the dipole
moment surfaces have been used to calculate infrared absorption intensities. The simple model
has been improved by including the most important large amplitude intermolecular motions by
perturbation theory. A similar model (without large amplitude motions) with the same kinetic
energy operators for adsorbed species has been employed. The potential energy surfaces have
been computed with density functional theory including periodic boundary conditions. The
results for the complexes have been compared with experimental gas phase infrared and matrix
isolation spectroscopic data. Using calculated shifts from the gas phase values to the adsorbed
molecules, we have obtained good agreement with experimental fundamental wavenumbers.
References
1. T. Salmi, V. Hänninen, A. L. Garden, H. G. Kjaergaard, J. Tennyson and L. Halonen, Calculation of the
OH stretching vibrational overtone spectrum of the water dimer, J. Phys. Chem. A 112, 6305-6312 (2008).
Erratum: J. Phys. Chem. A 116, 796–797 (2012).
2. T. Salmi, H. G. Kjaergaard and L. Halonen, Calculation of overtone O–H stretching bands and intensities
of the water trimer, J. Phys. Chem. A 113, 9124-9132 (2009).
3. T. Salmi, E. Sälli and L. Halonen, A nine-dimensional calculation of the vibrational OH stretching and
HOH bending spectrum on the water trimer, J. Phys. Chem. A 116, 5368−5374 (2012).
4. E. Sälli, T. Salmi and L. Halonen, Computational high-frequency overtone spectra of the water ammonia
complex, J. Phys. Chem. A 115, 11594–11605 (2011).
5. E. Sälli, J.-P. Jalkanen, K. Laasonen and L. Halonen, Computational study of adsorption and the
vibrational properties of water on the Cu(110) surface, Mol. Phys. 105, 1271-1282 (2007).
6. E. Sälli, V. Hänninen and L. Halonen, Variationally calculated vibrational energy levels of ammonia
adsorbed on a Ni(111) surface, J. Phys. Chem. C 114, 4550–4556 (2010).
7. E. Sälli, S. Martiskainen and L. Halonen, Computational study of the vibrational structure of the
ammonia molecule adsorbed on the fcc (111) transition metal surfaces, J. Phys. Chem. C 116, 14960–
14969 (2012).