The p(1 x 1) adsorption of atomic oxygen on the fee and hcp three-fold holl
ow site of a Pt(lll) surface has been investigated by a periodic slab model
, varying the number of layers from two to four. The density functional met
hod with local spin density approximation and with generalized gradient exc
hange-correlation functionals was employed using the CRYSTAL95 ab initio pr
ogram. It was found that the three-layer slab model was a good compromise b
etween accuracy and the computational time. The LDA/VWN calculations predic
t that the fee-hollow site is energetically preferable by 0.29 eV compared
to the hcp-hollow site. This preference is also supported by experimental d
ata. Oxygen p(1 x 1) heat of adsorption of 0.61 eV calculated with the BPW9
1 method is in reasonable agreement with the experimentally estimated one.
The corresponding equilibrium adsorbate-surface distance is 1.25 Angstrom.
Density-of-states analysis demonstrates that the formation of the Pt-O bond
is mainly due to the interaction of Pt 5d(xz) and 5d(yx) orbitals of the s
urface platinum atom and 2p(x) and 2p(y) orbitals of the oxygen adatom. Thr
ee-dimensional difference electron density plots indicate a delocalized int
eraction of the oxygen adatoms to the surface.