Using a tight-binding, total-energy model, we predict the atomic and electronic structure of the relaxed (1×1) corundum (0001) surface. The surface shows a large, bond-length-conserving relaxation, which is allowed by the topology of the surface. The relaxation is driven by a rehybridization of the surface Al atoms to ${\mathit{sp}}^2$, and an accompanying drop in the energy of occupied surface states, during the relaxation. Displacements of surface atoms from bulk positions are as large as 0.7 Å, and should be observable using a low-energy electron diffraction intensity analysis. Full relaxed atomic positions are reported, as well as a wavelength-resolved surface band structure, including orbital characters of surface states.

• Received 1 September 1993

DOI:https://doi.org/10.1103/PhysRevB.49.7691