Stability of a flexible polar ionic crystal surface: metastable alumina and one-dimensional surface metallicity.
A first-principles study of kappa-Al2O3 (001) and (001-) reveals new features of ion-surface stability and electronic structure. The need to generalize Tasker's rules for surface stability of low-symmetry crystals is shown. Structurally, the presence of bulk tetrahedral Al ( Al(T)) causes giant surface relaxations, with O termination at (001). Surface-layer Al(T) are strongly unfavored. This is understood with Pauling's rules and thus generally applicable to metastable aluminas. The bulk charge asymmetry and Al-sublattice anisotropy caused by the Al(T) create a 1D metallic surface state at (001-).
Ruberto
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C
Department of Applied Physics, Chalmers University of Technology and Göteborg University, SE-412 96 Göteborg, Sweden.
Yourdshahyan
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Y
Lundqvist
B I
BI