RELATIVE STABILITY OF TERNARY ADSORPTION SITES ON (111)FCC AND (0001)HCP TRANSITION-METAL SURFACES

In order to shed some light on the problem of crystal growth we here p resent a theoretical study of the relative stability of ternary adsorp tion sites on a close-packed surface of a hcp or fcc transition metal. We find that on Ir(111) the relative stability of the normal and faul t sites varies with the nature of the adatom, which is in very good ag reement with experiments: a single Ir adatom prefers the fault site, w hile an adatom with a larger d-band filling is more stable at a normal site. A similar calculation is carried out on Ru(0001) and prediction s are made concerning the relative stability of these two adsorption s ites.