α-Al2O3 Slabs: a local environment study

G. N. DARRIBA; R. FACCIO; M. RENTERÍA

La Plata

Conferencia; Humboldt kolleg- International Conference on Physics; 2011

In this work we performed an ab initio/DFT study of structural and electronic properties of the (001) α-Al2O3 surface. For this study we used two methods with different basis set: the Augmented Plane Wave plus local orbital (APW+lo) and a linear combination of numerical localized atomic orbital basis sets, employing the Wien2K code and SIESTA code, respectively. In order to calculate the structural and electronic properties of the reconstructed surface, we calculated the final equilibrium atomic positions with the SIESTA code and then we calculated the Electric-Field Gradient (EFG) tensor with the APW+lo code at the optimized positions. Using this procedure we found equilibrium structures with less energy than those obtained by using only the APW+lo method. The EFG tensor and the local structure for Al were study as a function of the depth from the surface, for relaxed structures. We found that distances down to 6 Å from the surface are sufficient to converge the EFG and the Al-O distances to bulk values. The predicted bulk EFG is in good agreement with the experimental results. These results can be used for local probe purposes, for example in the case of doping, with important sensitivity for probes located close to the top of the surface, in particular for distances lower than 6 Å.