INTERACTION OF THE METHOXY RADICAL WITH COPPER SURFACES - COMPARATIVE CLUSTER MODEL STUDIES

Model calculations on Cu3OCH3 clusters for various lateral adsorption sites are performed to study the details of the chemisorptive interaction of methoxy (OCH3) with Cu(111) surfaces. The calculations are based on the ab initio Hartree-Fock method using all-electron Gaussian basis sets. The results suggest that OCH3 stabilizes at three-fold central sites of Cu(111) which is consistent with experimental findings. The OCH3-Cu interaction is described by small OCH3 to Cu charge transfer involving the OCH3 5a1 orbital and a much larger Cu to OCH3 back-transfer filling the OCH3 2e lone pair orbitals. As a result, the adsorbate species becomes negatively charged in the cluster and the rather large OCH3-Cu binding energy (1.7 eV) contains ionic and covalent contributions of about the same magnitude.