Ab initio study of the electric-field gradient at Cd-doped SnO

L. A. ERRICO, M. RENTERÍA, AND H. M. PETRILLI.

Foz Do Iguazu, Brasil

Conferencia; XIV International Conference on Hyperfine Interactions & XVIII International Symposium on Nuclear Quadrupole Interaction; 2007

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Hyperfine techniques, and in particular - Time-Differential Perturbed-Angular-Correlation (TDPAC) spectroscopy,have been increasingly applied to condensed-matter problems through the precise characterization of theelectric-field-gradient (EFG) tensor at diluted (ppm) radioactive probe atoms, adequately introduced at substitutionalhost lattice sites. The single-atom counting of this technique, in combination with its highly localized sensitivity (dueto the r−3 dependence of the electric-quadrupole interaction), allows a detailed investigation of both structural andelectronic properties of the systems under study. Generally, the probe is an impurity dopant in the host. For thisreason, interpreting TDPAC experimental results involves the understanding of the chemical differences between theimpurity probe atom and the indigenous ion replaced by the impurity. For an accurate calculation of the structuraland electronic properties of the doped system, the electronic configuration of the host, perturbed by the presenceof the impurity, has to be determined what requires the use of a state-of-the-art ab initio electronic structure calculation.In this work we report a Density Functional Theory (DFT) study of the EFG at Ta impurities located atthe cation site in the semiconductor SnO using the Full-Potential Linearized-Augmented Plane Waves (FPLAPW)method. The predictions for the EFG tensor are compared with available experimental TDPAC results and withrecent DFT calculations performed for Cd-doped SnO. In this way we can compare the electronic structure and thestructural relaxations introduced by acceptor (Cd) and donor (Ta) impurities when they replace cations in SnO. Weconsider different charge states for the impurity and study the dependence of the electronic properties and structuralrelaxations on these charged states. Our combined experimental-ab initio approach adds to the systematic study ofthe role played by metal impurities in semiconductor oxides which we have been performing.