First-principles calculations of the EFG at Ta sites in Cr2O3:Ta semiconductor

G. N. DARRIBA; E. L. MUÑOZ; L. A. ERRICO; D. RICHARD; P. D. EVERSHEIM; M. RENTERÍA

Arhus, Dinamarca

Workshop; Quantum Theory of Solids (QTS-5). International Workshop; 2009

Self-consistent electronic structure APW+lo calculations in the dilute (1:12) Cr2O3:Ta system (corundum phase), improving the previously reported dilution (1:4) [1], are reported here using the WIEN2K code. The calculations were carried out for different magnetic configurations and different charge states of the impurity. The EFG predictions at Ta impurity sites are compared with the EFG results coming from recent Perturbed-Angular-Correlation (PAC) experiments performed on 181Hf(™181Ta)-implanted Cr2O3 polycrystalline samples. The results for the EFG at Ta sites in Cr2O3 are also compared with EFG results at 111Cd and 181Ta impurity sites in the isomorphous a-Al2O3 and a-Fe2O3 semiconductors. This combined study enables the determination of lattice relaxations induced by the presence of the impurity in the host lattice and the charge state of the impurity donor level (Ta 5d) introduced in the band gap of the semiconductor.   [1] G.N. Darriba et al., Physica B (2009), in press.