FP-LAPW Study of Pure and Cd-Dopped Indium Metallic Surfaces

L.A. ERRICO; M. WEISSMANN; M. RENTERÍA

Pucón

Conferencia; XI Latin American Congress of Surface Science and its Applications; 2003

Universidad de Chile

Structural and electronic properties at and near surfaces are important to understand the interaction of atoms under these special boundary conditions. In particular, the reconstructions and  surface states are being studied for both basic and technological reasons. For example, changes of the electronic properties between different atomic layers (or even between atoms in the same layer) are of fundamental interest. One way to obtain electronic properties on an atomic scale is offered by hyperfine experimental techniques. In particular, g-g Perturbed-Angular Correlations (PAC) provides a high resolution determination of the electric- field-gradient (EFG) tensor at the site of a probe-atom, a magnitude particularly sensitive to slight local changes in the electronic charge density around the probe. With this technique, monolayer-resolved studies are possible [1]. The measured EFG could give structural and electronic information of the system that cannot be obtained by other methods, but their interpretation is not straightforward. All-electron ab-initio calculations, based on density functional theory, have been successfully used by us as a complementary tool for the investigation of the EFG at impurities in oxides [2-4]. The purpose of this communication is to present a first-principles study of the electronic and structural properties of pure and Cd-dopped Indium metallic surfaces. The EFG at the Cd impurity replacing an Indium atom of the bulk and of the surface are  also calculated in order to validate the theoretical results by means of the comparison with 111Cd PAC experimental results. The study was performed  with the WIEN97 implementation, developed by Blaha et al. [5], of the full-potential linearized-augmented-plane-wave (FP-LAPW) method. It considers no shape approximation on either the potential or the electronic charge density, being thus specially suited for EFG calculations. In order to approximate the dilution of the Cd impurity we used supercells of increasing size, all containing a single Cd atom, and calculated the self-consistent potential and charge density inside each one. We studied the relaxation introduced by the impurity by computing the forces on the Cd neighbors and moving them until the forces vanished. For the surface cases we studied first the reconstruction of the pure In metal surfaces and then study the effect of replacing one In atom by a Cd impurity. Finally, we compare the results with the experimental PAC data [1].   This research was partially supported by Fundación Antorchas, ANPCyT (PICT 03-03727), CONICET, Argentina, and TWAS, Italy.     References   [1] W. Körner, W. Keppner, B. Lehndorff-Junges, and G. Schatz, Phys. Rev. Lett. 49, 1735 (1982). [2] L. A. Errico, G. Fabricius, and M. Rentería, Hyperfine Interac. 136/137, 749 (2001). [3] L. A. Errico, G. Fabricius, M. Rentería, P. de la Presa, and M. Forker, Phys. Rev. Lett. 89, 55503 (2002). [4] L. A. Errico, G. Fabricius, and M. Rentería, Phys. Rev. B 67,  144104 (2003). [5] P. Blaha, K. Schwarz, P. Dufek, and J. Luitz, Wien97, (K. Schwarz, Technische Universtität Wien, Austria, 1999), ISBN 3-9501031-0-4.