VIBRATIONAL-SPECTRUM OF METHOXY ADSORBED ON METAL-SURFACES - AB-INITIO CALCULATIONS AND EXPERIMENTS

Ab initio electronic structure calculations are used to assign the vib rational spectra of methoxy adsorbed on Mo(110). Methoxy with two diff erent orientations with respect to the surface, perpendicular (C-3v) a nd tilted (C-s), were investigated. Using calculations on Mo-methoxy a nd Rh-methoxy complexes to represent different orientations and symmet ries, it is shown that experimentally observed changes in spectra asso ciated with reorientation and isotopic substitution (CH3O-, CHD2O- and CD3O-) are reproduced completely by the calculations. Problems with t he use of vibrational data on gas-phase species for interpreting surfa ce data are presented. Limitations in the approach associated with Fer mi resonances are discussed. (C) 1997 Elsevier Science B.V.