First-principles calculations for the surface termination of pure and yttria-doped zirconia surfaces

First-principles calculations for tetragonal zirconia are presented. The stability of the terminations is investigated for different setups (symmetrically or asymmetrically terminated or metal supported) and as function of the film thickness. Several aspects, which are of importance for polar surfaces, are discussed on the basis of the results from the asymmetric setup. Among other things the dielectric constant can be derived from the slab calculations. For the more stable (101) surface a surface phase diagram under hydrogen and oxygen atmosphere is presented. Finally, the interaction between yttrium dopants and the surface is analyzed. While such defects prefer positions far from the surface for a (001) oriented surface, the more stable (101) surface becomes even more stabilized by defects close to the surface. This result is in agreement with experimental findings.