  The adsorption of CO on the Pt(111) surface in a root3 x root3 pattern has
been studied with the gradient corrected functional of Perdew and Wang and the
B3LYP hybrid functional. A slab which is periodic in two dimensions is used to
model the system. The Perdew-Wang functional incorrectly gives the fcc site as
the most favorable adsorption site, in accord with a set of previous studies.
The B3LYP functional gives the top site as the preferred site. This confirms
results from cluster studies where it was suggested that the different
splitting, dependent on the functional, between highest occupied and lowest
unoccupied molecular orbital, could be the reason for this change of the
adsorption site. This is supported by an analysis based on the projected
density of states and the Mulliken population.
