The atomic geometry and the core-level shifts of an Sb monolayer adsorbed on the GaAs(110) surface have been determined using the pseudopotential density-functional theory. The results clearly favor the epitaxial continued layer structure (ECLS) model, and demonstrate the need to include the Ga partial-core correction for both the GaAs bulk lattice constant and the Sb-Ga bond length. Furthermore, within the ECLS geometry, both the initial- and the final-state model calculations lead to the same conclusion that the $4d$ core-level binding energy of an Sb atom bonded to Ga shifts downwards by about 0.4 eV relative to that of an Sb bonded to As. These findings provide the theoretical basis for the interpretation of recent photoelectron diffraction experiments.

• Received 23 July 1997

DOI:https://doi.org/10.1103/PhysRevB.57.1352