Relativistic effect on the interatomic platinum-oxygen potential and its consequences in high energy O2/Pt(111) scattering

The influence of relativity on the binding in the Pt–O molecule is investigated using density functional calculations and proves to be quite important, not only for the potential well but also for the repulsive wall. Using a Born–Mayer fit to this interatomic gas phase potential, we perform a classical trajectory study on high energy O2/Pt(111) scattering (Ei=80 eV). The Born–Mayer form of the interatomic potential leads to a higher degree of dissociation for O2/Pt(111) than for O2/Ag(111) which is also experimentally found. The role of relativity turns out to be significant. The dissociation mechanism, however, does not change when going from O2/Ag(111) to O2/Pt(111). The molecules were found to first gain primarily rotational energy, which is largely transfered to vibration at the turning point of the second atom, in the case of finally dissociating molecules. Since the calculated dissociation in the case of platinum is still less than found experimentally, we investigate the influence of better fits to the interatomic potential, as well as inclusion of the potential well. It is possible to improve agreement with the experimental results by directly reducing the long range of the Born–Mayer potential.