OVERLAYER AND INTERFACE RESONANCES AND BOUND-STATES AT PD/AG(001) AND AG/PD(001) SURFACES

We have calculated the k(\\)-, symmetry-, and. layer-resolved density of states (DOS) at k(\\) = O for complete pseudomorphic monolayers of Pd on Ag(001) and Ag on Pd(001). For the xy and x(2) - y(2) subbands, which do not hybridize with any other low-lying orbitals, the resulting DOS agrees quantitatively with that of a 1D-semi-infinite chain perturbed only at the overlayer, i.e. terminal, site and at the interface, i.e. penultimate, site. The Pd overlayer presents a repulsive potential to the silver. This results in a surface (overlayer) state strongly bound above each subband, in pushing an existing surface (x(2) - y(2)) state on pure Ag(001) further above the band and in converting an existing resonance (xy) into an interface bound state. The Ag overlayer on the other hand presents an attractive potential to the Pd, resulting in a bound state below each subband and greatly weakened interface resonances at the subband tops.