Coordination to transition metal surfaces : a theoretical study

A theoretical framework is developed that describes the chemisorption of CO to transition metal surfaces analogous to the HOMO-LUMO concept of MO theory. An explanation is given for the exptl. observation that CO adsorbs on top at the (111), face of Pt, but bridge at the (111) face of Ni. One is due to differences in the interaction with the d-valence electrons. Adsorption of K changes the relative position of the adsorbate levels with respect to the Fermi level of the metal due to the pos. charge of adsorbed K. This changes the balance of the donating and back donating contributions to the adsorption energy of CO and tends to favor bridge coordination on Pt as found exptl. The factors detg. top or multiple adsorption of H were analyzed