CHEMISORPTION OF A P-ADSORBATE ON PEROVSKITES

The chemisorption of an oxygen adatom on the (001) surface of a perovs kite crystal is examined parametrically. An empirical tight-binding me thod is used in the calculations. The adatom is assumed to chemisorb i n a head-on position to the surface cation and the effects of the foll owing parameters are investigated: the orbital interaction V(p) betwee n adatom and surface cation, the difference DELTAE(d) in the self-ener gies of a surface cation and a bulk one, and the local perturbation DE LTAw0 on the self-energy of the surface cation that participated in th e chemisorption bond. As a result of chemisorption the oxygen adatom s hares the delocalized surface states of the perovskite, and in additio n to that two peaks appear next to the surface states, one below the s urface band being a bonding state and one above it, being an antibondi ng state. The change in chemisorption energy with the adatom-surface i nteraction strength has been investigated.