A. Seeger et al., ELECTRIC-FIELD GRADIENTS AROUND POINT-DEFECTS IN METALS, Zeitschrift fur Naturforschung. A, A journal of physical sciences, 51(5-6), 1996, pp. 489-505
The splittings of nuclear energy levels caused by the electric field g
radients acting on the quadrupole moments of nuclei in the neighbourho
od of atomic defects in cubic metals may serve as ''fingerprints'' pro
viding us with a unique characterization of these defects. In favourab
le cases the NQDOR technique (nuclear quadrupole double resonance) per
mits sensitive measurements of these splittings with good resolution.
The present paper outlines the status of the ab-initio calculation of
electric field gradients with emphasis on the theoretical basis (densi
ty functional theory with local density approximation) and on the tech
niques required for handling the specific problems associated with def
ects. Recent work by the supercell approach on atomic defects in Al an
d Cu, making use either of the full-potential linearized augmented-pla
ne-wave method or of the ab-initio pseudopotential method, are reporte
d and compared with experiments. The excellent agreement between exper
iment and theory for the field gradients acting on the nearest-neighbo
ur nuclei of monovacancies in Al demonstrates the reliability and the
potential of the theory.