Local reactivity of metal overlayers: Density functional theory calculations of Pd on Au

The local reactivity of Pd overlayers supported by Au has been studied by calculating atomic hydrogen and CO adsorption energies as a microscopic probe. The calculations are based on density functional theory within the generalized gradient approximation. The binding energies show a maximum on two Pd layers on Au, both for the (100) and (111) surfaces. We have furthermore analyzed local trends by considering different adsorption sites on the Pd overlayers. The results can be rationalized within the d-band model if also second-nearest-neighbor interactions and bond-length effects are taken into account.