Coordination dependence of hyperfine interactions at impurities on fcc metal surfaces. I. Electric-field gradient

We present a comparison between ab initio calculations and a high-quality experimental data set (1990- 2002) of magnetic hyperfine fields of Cd at different sites on Ni surfaces. The experimentally observed parabolic coordination number dependence of this hyperfine field is verified as a general trend, but we demonstrate that individual cases can significantly deviate from it. It is shown that the hyperfine fields of other 5sp impurities at Ni surfaces have their own, typical coordination number dependence. A microscopic explanation for the different dependencies is given in terms of the details of the s-DOS near the Fermi level.