A THEORETICAL-STUDY OF CHX CHEMISORPTION ON THE NI(100) AND NI(111) SURFACES

Cluster model calculations have been performed for CH(x), x = 0-3, chemisorbed on Ni(100) and Ni(111). The predicted chemisorption energies, at the present level of theory, based on bond-prepared clusters for Ni(100) are for carbon 150 kcal/mol, for CH 136 kcal/mol, for CH2 91 kcal/mol and for CH3 46 kcal/mol. The corresponding energies for Ni(111) are for CH 120 kcal/mol, for CH2 88 kcal/mol and for CH3 49 kcal/mol. These chemisorption energies lead to similar stabilities for all CH(x) fragments on both Ni(100) and Ni(111). Large basis sets multi-reference correlation treatments are found to be very important in particular for the multiply bonded species. The vibrational C-H stretching frequencies predicted for CH(x) on Ni(111) are for CH 3054 cm-1 (2980 cm-1), for CH2 3204 cm-1 and for CH3 2709 cm-1 (2680 cm-1), where the available experimental values are given in parenthesis. The predicted ionization spectra of adsorbed CH(x) are also in general agreement with experimental findings