Overlayer and interface resonances and bound states at Pd Ag(001) and Ag Pd(001) surfaces

We have calculated the k_{{norm of matrix}}-, symmetry-, and layer-resolved density of states (DOS) at k_{{norm of matrix}} = 0 for complete pseudomorphic monolayers of Pd on Ag(001) and Ag on Pd(001). For the xy and x² - y² 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 (x² - y²) 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.