Surface electronic structure for Al(111) by a scattering method

A scattering method is used to calculate the surface band structure of Al(111) from 8.6 eV below the Fermi level to 9 eV above it. This method has rarely been implemented previously. The complete complex bulk and surface band structure is also shown for key values of the crystal surface-parallel momentum. The surface region is treated semi-empirically from a small number of experimentally determined quantities. We find agreement over the whole surface Brillouin zone for surface states compared with recent theoretical ab initio results and experiment. Differences with respect to surface resonances detected by recent theoretical methods are discussed. In particular a class of surface resonances is detected here that may be surface-layer localised and results from very wide partial surface-projected energy gaps where real lines in the complex bulk band structure extend from band minima to infinity. Other methods do not appear to have detected these resonances. They may have an effect on photoemission intensity profiles and may account for previous unexplained experiment features considered to be "a kind of surface enhancement at partial gap edges". This scattering method provides a single picture for the formation and classification of surface states and resonances.