Electronic structureof alpha-Al2O3 slabs: A local environment study

G. DARRIBA; R. FACCIO; M. RENTERÍA

PHYSICA B - CONDENSED MATTER

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2012 p. 3093 - 3095

0921-4526

In this work we performed an ab initio / Density Functional Theory (DFT) study of structural and electronic properties of the (001) alpha-Al2O3 surface.For this study we used two methods with different basis set: the Full-Potential 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 calculate the structural and electronic properties of the reconstructed surfaces, we calculate the final equilibrium atomic position with the SIESTA and then the electric-field gradient (EFG) at Al site was calculated with the FP-APW+lo code using the optimized positions. Using this procedure we found equilibrium structure with comparative lower energy than those obtained using only the FP-APW+lo method. The EFG tensor and the local structure for Al was studied as a function of the depth from the surface for the relaxed structures. We found that distances down than 6 A from the surface are sufficient to converge the EFG and the Al-O distances to bulk values. The predicted bulk EFG at the Al site is in good agreement with the available experimental values. These results can be used for local probes purposes, e.g., in the case of doping, with important sensitivity for probes locate close to the top of the surface, in particular for distances smaller than 6 A.