Over the last decade, there has been considerable interest on the chemistry of methanol on transition metal surfaces, inspired in part by the use of copper as a catalyst in methanol synthesis.^1-4 The adsorption and decomposition of methanol have been investigated on a variety of surfaces for example, Ag(110, 111), Au(110), Cu(100, 110, 111), Pt(100, 110), Ni(100, 110, 111). In all surfaces the dominant surface intermediate is the methoxy radical that is easily formed by cleavage of O-H bond of methanol. Unfortunately, experimental data allow conflicting interpretations in what concerns the orientation of the methoxy radical on the surface. Theoretical work is required to clarify the local interaction of methoxy with the surface and the reaction mechanisms where it takes part.

In this poster, DFT calculations (with Becke3LYP hybrid method) of some chemisorption properties for different M_nCH₃O clusters at the M(111) surface, with M= copper, silver and gold, are reported. The influence of the nature of the metal surface on chemisorption and on the vibrational frequencies is discussed.

It is shown that the behaviour of radical at the surface is different on the three metallic surfaces studied. Our results are in good agreement with available experimental data.

We thank JNICT and PRAXIS XXI for financial support.

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4. - H. E. Dastoor, P. Gardner e D. A. King, Chem. Phys. Lett. 209 (1993) 493.