Electronic Structure of Cd impurities in (001) alpha-Al2O3 Slabs: a local environment study

G. N. DARRIBA; R. FACCIO; M. RENTERÍA

Villa de Leyva

Congreso; SLAFES XXI; 2013

In this work we performed an ab initio/DFT study of structural and electronic properties of the (001) alpha-Al2O3:Cd surface. The Cd impurities were placed at the different Al substitutional sites as a function of the depth from the surface. For this study we used two methods with different basis set: Full-Potential the Augmented Plane Wave plus local orbital (FP-APW+lo) and a linear combination of numerical localized atomic orbital basis sets, employing the WIEN2k code and the SIESTA code, respectively. In order to reconstruct the surface, we calculated in each case 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. This procedure has already been demonstrated successful in the case of pure alpha-Al2O3 slabs [1]. The EFG tensor and the local structure at Cd sites were studied 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 for converge the EFG and the Cd-O distances to bulk values of the Cd-doped Al2O3. The predicted bulk EFG is in good agreement with the experimental (111In)111Cd PAC results. [1] G. N. Darriba, R. Faccio, and M. Rentería, Physica B 407, 3093 (2012).