Effect of lattice relaxations on the hyperfine fields of heavy impurities in Fe

We present first-principles calculations of hyperfine fields of heavy impur ities in BCC Fe. In particular. the effect of lattice relaxations on the ca lculated hyperfine fields are studied. The calculations are based on a full -potential Korringa-Kohn-Rostoker Green's function method for defects and e mploy the local spin-density approximation for the exchange and correlation effects. The non-spherical parts of the potential and the charge density a re treated correctly, while the forces are calculated by an ionic version o f the Hellmann-Feynman theorem. Lattice statics methods are used to describ e the longer ranged relaxations. The calculated hyperfine fields of 5sp and 6sp elements are compared with the available experimental data and it is s hown that the inclusion of lattice relaxations in the calculation improves the agreement with experiments. (C) 2001 Elsevier Science B.V. All rights r eserved.