Structural and vibrational properties of Ni(111)/NO adsorption complexes: a LCGTO-LDF model cluster investigation

The vibrational spectra and structural data for molecular adsorption of NO at the Ni(111) surface are analyzed with the help of first-principles LCGTO-LDF cluster models. The calculations support the interpretation of the vibrational bands observed below 1500 cm^-1 as a manifestation of the nitrosyl species bound upright to the threefold hollow sites. Bent and tilted structures of the adsorbate are energetically less favoured. Slightly higher N-O vibrational frequencies are computed for molecules adsorbed in the twofold bridge position. Investigations of the lateral interactions are necessary to find out if the vibrational bands around 1580 cm^-1 are related to the bridging NO species. The assignment of the RAIRS peak near 1680 cm^-1 to vibrations of NO in the on-top position is not confirmed by the present study.