  A lattice gas model is used to study the equilibrium properties and
desorption kinetics of CO on Ru(0001). With interactions obtained from density
functional theory (DFT) the phase diagram and temperature programmed desorption
(TPD) spectra are calculated up to a coverage of 1/3 ML using top sites only.
For coverages beyond 1/3 ML hollow sites are included. Good agreement is
obtained between experiment and theory for coverages below 1/3 ML using top
sites only. When including hollow sites, DFT calculations fail in predicting
the correct binding energy differences between top and hollow sites giving
disagreement with TPD, low energy electron diffraction (LEED) and heat of
adsorption experiments.
