Ab initio calculation of forces and lattice relaxations in metallic alloys

We present first-principles calculations of forces and lattice relaxations in bce Fe. In particular, relaxations around 3d, 4d and 5d transition metal impurities are calculated. The calculations are based on a full-potential Korringa-Kohn-Rostoker Green's function method for defects and employ the l ocal spin density approximation for the exchange and correlation effects. T he nonspherical parts of the potential and the charge density are treated c orrectly, while the forces are calculated by an ionic version of the Hellma nn-Feynman theorem. Lattice statics methods are used to describe the longer ranged relaxations. The results are compared with lattice parameter measur ements for the volume changes. Because of the correct treatment of the shar p shape of the Wigner-Seitz cell, the angular momentum expansion coefficien ts of the cell potential have discontinuities in the first derivative, whic h cause some complications when solving the radial equations. An effective method to get around these discontinuities is introduced.