BONDING MECHANISM AT BIMETALLIC INTERFACES - PD OVERLAYER ON VARIOUS SUBSTRATES

The mechanism responsible for bimetallic bonding in Pd/Ta(110), Pd/W(1 10), Pd/Re(0001), and Pd/Ru(0001) is investigated using the local-dens ity full potential linearized augmented-planewave method with the atom ic force approach. Charge polarization induced in the Pd layer by the substrate is found to play the key role: the resulting potential barri er in the interfacial region reduces the energies of the valence and c ore states of the Pd adatoms, which alters the electronic properties o f the Pd overlayer significantly [such as a tenfold reduction of the d ensity of states at the Fermi level for Pd/Ta(110)]. Close relationshi ps are found between the bonding energies and the core-level shifts an d the value of the density of states at the Fermi level for the system s studied, which may be important for understanding the chemisorption of CO on these bimetallic systems.