Abstract
First-principles calculations are performed on the stable and metastable phases to understand the stability and bonding of the flexible alumina surfaces. The (001) and surfaces of are investigated and compared to A needed extension of the original formulation of the Tasker’s rule for the stability of low-symmetry ion-crystal surfaces is found. Also, use of extended Pauling’s rules makes the results applicable to other metastable alumina phases. The most stable termination of is found to be in the middle of an Al layer, similarly to This surface is shown to be nonpolar, even though a Tasker point-charge description implies a polar classification. The asymmetry in atomic and electronic structures introduced by the tetrahedrally coordinated Al ions is found to have important consequences for the surface properties. The bulk cation-vacancy lines caused by the make the surfaces more open than thus allowing a huge inward relaxation at making this surface O terminated. The charge asymmetry in bulk causes an excess of electrons at yielding a one-dimensional metallic surface state. Also, the presence of in the near-surface layer is found to be destabilizing.
- Received 6 August 2002
DOI:https://doi.org/10.1103/PhysRevB.67.195412
©2003 American Physical Society