TENSOR LEED ANALYSIS OF THE NI(111)-P(2X2)-CH3CN STRUCTURE

The adsorption of acetonitrile on Ni(111) leads to an ordered (2 x 2) overlayer. In the first detailed surface structure determination of organic molecules containing both C and N, LEED intensity versus energy (I-V) curves for this structure have been measured and analyzed using an automated search method based on the tensor LEED approximation. The adsorbed acetonitrile is bound to the surface by both carbon and nitrogen with its C-N axis almost parallel to the metal surface. The adsorbed acetonitrile rehybridizes on the surface, becoming non-linear with a C-C-N angle estimated at 123-degrees. This structure is in accordance with models which were proposed from HREELS and XPS studies for acetonitrile adsorbed on platinum and nickel surfaces. It is also somewhat similar to the structure of nitriles in tri-iron and tri-osmium clusters. A slight adsorbate induced relaxation of the surface nickel atoms is also observed.