GRADIENT CORRECTIONS IN FIRST-PRINCIPLES CALCULATIONS OF HYPERFINE PARAMETERS IN SEMICONDUCTORS

The spin-polarized density-functional method with a plane-wave basis s et is used to investigate the microscopic structure and, in particular , the hyperfine parameters of hydrogenlike impurities in silicon and d iamond. Both the bond-centered and the tetrahedral interstitial impuri ty sites are investigated. These electronic-structure calculations are performed on a highly converged level in terms of the supercell size and the quality of the basis set. The magnitudes of the spin densities at the impurity are underestimated by the local-density approximation . However, with exception of the next-nearest-neighbor Fermi contact t erm, further study using gradient corrections in the exchange-correlat ion energy and accounting for the zero-point motion of the impurity yi elds hyperfine parameters that are in very good agreement with the exp erimental values.