The appearance and disappearance of the Shockley surface state on Cu(lll) i
s studied as a function of density and width of extended adsorbed defects u
sing a Hamiltonian that contains s, p, and d orbitals in the basis. The loc
al electronic density of the surface state at the Gamma point is obtained a
tom by atom. We also report on one- and two-dimensional defect states lying
near the Fermi level.