%'e report the results of surface electronic-structure calculations for the three low-index faces of elemental Pb. To our knowledge, these are the first calculations for the Pb(110) and Pb(111) surfaces addressing their electronic structure. The underlying bulk crystal is described by a realistic secondnearest-neighbor empirical tight-binding Hamiltonian which includes s and p orbitals and takes spinorbit coupling into account. The resulting 6sand 6p-derived bands are entirely decoupled. Our Hamiltonian yields the bulk density of states and the occupied bulk energy bands in excellent agreement with the data from x-ray and angle-resolved ultraviolet photoelectron spectroscopy measurements. The electronic structure of the (001), (110), and (111)surfaces is calculated for semi-infinite systems employing the scattering theoretical method. Our calculations predict a number of occupied as well as empty surface states or resonances in the energy regions of both the sand p-band projections. All three surfaces show a pronounced resonance around -8 eV and a band of bound surface states near -2 eV below E+.There are no surface states in the gap between the occupied s and p bands. For exemplary cases we highlight the origin and nature as well as the spatial localization of characteristic surface features.

Submonolayer adsorption of group-IV elements (Ge, Sn, Pb) on the Ge(111) surface has been investigated using first-principles pseudopotential total-energy and force calculations. The most prominent adsorption geometries, namely T4 and H3, are compared with respect to their atomic and electronic structure. As the most striking result, our calculations favor adsorption of adatoms in thresfold-symmetric T4 sites for all three different adatom species in agreement with earlier predictions and experiment.

The results of an empirical tight-binding study of the electronic properties of Al surfaces are reported. The underlying bulk crystal is described by a realistic first-nearest-neighbour empirical tight-binding Hamiltonian which includes s-, p-, and d-orbitals. The electronic structure of the (OOl), (1 lo), and (1 11) surfaces is calculated for semi-infinite systems employing the scattering theoretical method. Our results are compared with the results of other calculations and with experimental data. For a few representative cases we analyse the origin and nature as well as the spatial localization of the surface states.