INVESTIGADORES
ERRICO Leonardo Antonio
congresos y reuniones científicas
Título:
PAC experiments at impurity sites in synglecrystals: checking electronic structure ab initio calculations in doped-semiconductors
Autor/es:
M. RENTERÍA, G.N. DARRIBA, L.A. ERRICO Y P.D. EVERSHEIM
Lugar:
Bonn, Alemania
Reunión:
Conferencia; XIII International Conference on Hyperfine Interactions & XVII International Symposium on Nuclear Quadrupole Interaction; 2004
Institución organizadora:
-
Resumen:
Recently,
ab initio electronic structure
calculation methods in the framework of the Density Functional Theory (DFT),
like the Full-Potential Linearized Augmented Plane Wave (LAPW), have
been applied for the first time to doped
semiconductors and, in particular , to oxide semiconductors with diluted
impurities, enabling the description of
structural and electronic properties of these complex systems. The LAPW method
is one of the more accurate methods at present to calculate the electric-field
gradient (EFG), due to the very good description of the electronic density near
the probe-nucleus.
In this work we show how g-g Perturbed-Angular-Correlation (PAC)
experiments are an excellent test of the approximations used in DFT. In
particular, we present PAC results in TiO2 synglecrystals implanted with 181Hf ions at the
ISKP and measured at La Plata
with a high resolution and efficiency fast-fast spectrometer, in the
temperature range RT-1273 K. The magnitude, asymmetry, and orientation of the measured EFG tensor at Ta sites with respect to
the TiO2 crystal axis are compared with the first ab initio calculations at Ta impurities
in an oxide, TiO2, and to experimental and theoretical results at Cd
and Ti sites in TiO2. The confidence obtained for the theoretical
calculations enables the determination of the EFG sign, not affordable with
conventional PAC experiments.