S. Papadia et al., STRUCTURAL STABILITY OF ADATOM ISLANDS ON FCC(111) TRANSITION-METAL SURFACES, Physical review. B, Condensed matter, 54(20), 1996, pp. 14720-14727
The energetics of monomer; dimer, and triangular trimer adatom islands
on the (111) surface of fee transition metals of the same chemical sp
ecies is calculated in the tight-binding scheme as a function of the d
band filling. Both the adatom and their nearest neighbor substrate at
oms are allowed to relax. We investigate all possible atomic configura
tions of the system arising from the existence of (a) two types of ads
orption sites: normal (fee) and fault (hcp) sites, and (b) both types
of borders that may exist for triangles of adatoms: A, having (001), (
010), and (100) facets and B, having (11(1) over bar), (1(1) over bar1
$), and (<(1)over bar 11>) facets. It is found that there is an invers
ion of relative stability from fault to normal sites when the d band f
illing is larger than 8.2d electrons per atom for monomers, 7.85 for d
imers, 7.5 for trimers of type A, and 7.6 for trimers of type B. There
is also an inversion of stability for trimers from type B to type A w
hen the d band filling is larger than 7.95. All these results an in ve
ry good agreement with experiments on Ir for which the d band filling
is similar or equal to 7.5--7.6: monomers and dimers prefer to stick a
t fault sites while trimers settle at both sites. Furthermore, triangl
es of type B are energetically more favored than triangles of type A.
The case of other transition metals is also discussed.