New correlation potential for the local-spin-density functional formalism II. Hyperfine structure contact term in free atoms

Abstract

Using the new parametrization for the correlation potential, which seems to be the best that is at present available within the local-spin-density (LSD) functional formalism, the Fermi contact term in light atoms (up to Ni) is calculated. Although an overall improvement of the previous LSD results is obtained, the discrepancy between theory and experiment remains rather large. It seems that the local approximation for exchange and correlation fails to predict such quantities as magnetic-moment density near the nucleus. It is also shown that the self-interaction correction does not remedy this failure. Further, the effect of the nonzero nuclear radius is investigated and found to be most important in the lightest atoms (e.g. a factor of 0.664 appears in the case of Li). This fact has been omitted in all previous calculations and throws doubt on the reported excellent agreement of the results of many-body perturbation theory with experiment. We also verify that the contact approximation of the Fermi contact term is really good enough.