A THEORETICAL-STUDY OF THE SITE OF CO DISSOCIATION ON FE(100)

Molecular orbital calculations have been made for a carbon atom, an oxygen atom, and a CO molecule interacting with a 12 atom iron cluster representing an Fe(100) plane. The most stable site for isolated C and 0 atoms is a fourfold symmetric hollow site. The potential energies for CO dissociating along a variety of reaction pathways were calculated. The most favorable dissociation site, i.e. the one giving the lowest activation energy, is a fourfold site over which the C and O atoms separate such that they each bond to a pair of Fe atoms on opposite sides of the site. Analysis of the various calculations indicates that when two adsorbing atoms interact with the same surface atom, a relatively high (unfavorable) energy is produced. For this iron surface the calculations indicate that the larger the number of surface iron atoms bonding to an atomic adsorbate, the greater the adsorption energy, i.e. multicenter bonding, is favored.