A first-principles model for electron-capture ``after-effects´´ in 111 Cd: In2O3

MARIO RENTERÍA; LEONARDO A. ERRICO; EMILIANO L. MUÑOZ; ANIBAL G. BIBILONI

CAC (CNEA), Buenos Aires , Argentina

Congreso; "At the Frontiers of Condensed Matter Physics III"; 2006

CAC (CNEA) y Depto. de Física (UBA), Argentina

The temperature dependence of the electric-field gradient (EFG) tensor at 111Cd  impurity sites in oxides with the bixbyite structure has been intensively studied by means of the PAC technique in the last twenty years. In these systems two reversible behaviors have been observed apparently depending if the cation has closed electronic shells (such as in Sc, In, and Y) or if it has incomplete shells as in the case of the rare earths: time-dependent (“dynamic”) hyperfine interactions and static interactions variable with temperature were found, respectively. In2O3 doped with 111In (which decay to 111Cd by EC) is the prototype of the first behaviour.  In this work we report DFT electronic structure calculations at Cd impurities located at both cationic sites C and D of the In2O3 semiconductor, performed with the FP-LAPW method with a dilution of 1:32. We studied the EFG at both cationic sites for different charge states of the impurities, and these results were found to be in excellent agreement with the experimental values. A model based in changes of the occupation of impurity gap energy levels localized near the top of the valence band is proposed to described the origin of the experimentally observed dynamic interactions in this impurity-host system.