Electric-field-gradient study at Cd impurities in the (111) In surface.

G.N. DARRIBA; R. FACCIO; M. RENTERÍA

La Plata

Workshop; 6th Workshop on Novel Methods for Electronic Structure Calculations; 2015

In this work we performedan ab initio study of the electronic structure of Cd impurities located in the(111) indium surface, in order to discuss the hyperfine interactions experimentally observed at the (111In→)111Cd impurity sites at the surface and inside the metal, at different depths from the surface.The experimental results are coming from Time-Differential Perturbed Angular Correlation experiments in metallic indium thin films, in which radioactive 111In atoms was deposited in the surface. After this, inactive indium was deposited in several layers in order to obtain 111In at different depths. The electric field gradient (EFG) observed at impurities located at the surface was four times larger than those observed at those located into the bulk.For this study we employed two ab initio methods with different implementations: the Full-Potential Augmented Plane Wave plus local orbitals (FP-APW+lo) and Projected Augmented Waves (PAW), employing the WIEN2k and VASP codes, respectively.The Cd impurity was localized at substitutional In site in the previously reconstructed (111) In surface, and for different depths from the surface. The double approach allows us to obtain the equilibrium structures, using VASP, in a shorter time and with less energy that those found using the WIEN2K code (at least in the case of surfaces). The APW+lo method allows us to predict it EFG with very high accuracy. From the good agreement between theoretical predictions and experimental results, we show the potentiality of the TDPAC spectroscopic technique to sense probes is the vicinity of the surfaces.