Bonding mechanism at bimetallic interfaces: Pd overlayer on various substrates

The mechanism responsible for bimetallic bonding in Pd/Ta(110), Pa/W(110), Pd/Re(0001), and Pd/Ru(0001) is investigated using the local-density full-potential linearized augmented-plane-wave method with the atomic force approach. Charge polarization induced in the Pd layer by the substrate is found to play the key role: the resulting potential barrier in the interfacial region reduces the energies of the valence and core states of the Pd adatoms, which alters the electronic properties of the Pd overlayer significantly [such as a tenfold reduction of the density of states at the Fermi level for Pd/Ta(110)]. Close relationships are found between the bonding energies and the core-level shifts and the value of the density of states at the Fermi level for the systems studied, which may be important for understanding the chemisorption of CO on these bimetallic systems.