IMAGE POTENTIAL STATES ON LITHIUM, COPPER AND SILVER SURFACES

The electronic structure of the Li(110) surface is calculated within t he self-consistent pseudopotential method. The calculation does not gi ve any occupied surface state. At the same time, unoccupied resonance surface states have been found at the <(Gamma) over bar> point and alo ng the <(PH) over bar> symmetry direction. Image potential slates with energies of E-1 = -0.73 eV and E-2 = -0.22 eV are predicted al the Ga mma point. For the description of the image potential stales, we propo se a one-dimensional model potential. The parameters of this potential are determined with the use of experimental (or first-principles calc ulation) values of the width and position of the energy gap at the <(G amma)over bar> point and the energies E-0 and E-1 of the surface state and first image potential state, respectively. Using this model poten tial, we study the binding energies, wave functions and lifetime of im age potential states on the Li(110), Cu(100), Cu(lll), Ag(100) and Ag( 111) surfaces. We also show that using the local part of the full, scr eened, non-local pseudopotential can produce incorrect results for the binding energy of the image slates. (C) 1997 Elsevier Science B.V.