A theoretical study of CH x chemisorption on the Ni(100) and Ni(111) surfaces

Abstract

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 CH 2 91 kcal/mol and for CH 3 46 kcal/mol. The corresponding energies for Ni(111) are for CH 120 kcal/mol, for CH 2 88 cal/mol and for CH 3 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 and 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 CH 2 3204 cm −1 and for CH 3 2709 cm −1 (2680 cm −1), where the available experimental values are given in parent The predicted ionization spectra of adsorbed CH x are also in general agreement with experimental findings.