Total-energy pseudopotential calculations were performed for a variety of structures of Al adsorbed on the GaAs(110) surface. For a coverage of one monolayer, only very small differences of the adsorption energy was found for a number of competing structures. In contrast to LCAO calculations, all these structures were found either to be metallic or to have only a very small band-gap. Total energy calculations were also made for a Ga-Al exchange reaction and for different structural models for half a monolayer coverage including a 2 x 1 reconstruction. In all cases, the adsorption energy was found to be less than the cohesive energy of bulk Al in FCC structure or the energy gain due to an exchange reaction, indicating the tendency for cluster formation, as observed experimentally, or penetration into the substrate. By means of density-of-states calculations it was shown that the Schottky barrier was already formed for the ordered half-monolayer case and was completed for one monolayer of Al on GaAs. The band gap was found to open for an asymmetric dimer in a 2 x 1 reconstruction which could explain experimental observations. Chemisorption of Aluminium on GaAs(110). W.G.Schmidt, G.P.Srivastava: Journal of Physics - Condensed Matter, 1993, 5[49], 9025-36