title: Computational study of the adsorption energetics and vibrational wavenumbers of NH3 Adsorbed on the Ni(111) Surface.
abstract: The structure and stabilities of NH(3) adsorbed on different sites of a Ni(111) surface are compared based on density functional, plane-waves calculations within a periodic framework. The surface has been modeled by 4- and 5-layer slabs with 2 x 2 and 3 x 3 unit cells. Calculated results are in good agreement with available experimental data, confirming the atop adsorption site to be the most favorable, with no preferred azimuthal orientation for the H atoms. For NH(3) adsorbed at the atop site, the one-dimensional potential energy profiles along the N-H and N-Ni bonds and the coupling between adjacent N-H bond oscillators have been calculated and fitted to an analytical expression using an accurate anharmonic potential model. Variational calculations have been performed to obtain frequencies for the N-H and N-Ni stretching vibrations and N-H stretching line widths. The model for calculating line widths has also been tested with CO adsorbed at the hcp hollow of the Ni(111) surface.
authors.affiliation: Laboratory of Physical Chemistry, P.O. Box 55 (A.I. Virtasen aukio 1), FIN-00014 University of Helsinki, Finland.
authors.forename: Theo
authors.initials: T
authors.lastname: Kurten
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Biczysko
authors.forename: Timo
authors.initials: T
authors.lastname: Rajamäki
authors.forename: Kari
authors.initials: K
authors.lastname: Laasonen
authors.forename: Lauri
authors.initials: L
authors.lastname: Halonen