Activated non-dissociative adsorption on a compound surface: CO on NiAl(110)

The experimentally observed large barrier of 0.67 eV for non-dissociative adsorption of CO on NiAl(110) is investigated by an ab-initio method. The adsorption process is modeled by moving CO in a quasistatic manner to the four high-symmetry adsorption sites of the NiAl(110) surface. A barrier of 0.43 eV is calculated for CO adsorption on the Ni-bridged site at a surface to C distance of 2.12 إ which, according to analysis of the results, is caused by the dominating repulsive interaction of Al sp states with the CO states. For the other adsorption sites studied, chemical bonding overcomes the repulsion.