Electronic correlations, magnetism, and structure of Fe-Al systems: An LDA+U study

The influence of electronic correlations on the intimate relations between magnetism and structure of Fe-Al subsystems is investigated by the LDA+U method in the two currently used versions, around mean field (AMF) and fully localized limit (FLL). The calculations were performed with the new Suttgart spin-polarized ab initio mixed-basis pseudopotential LDA+U code which is able to calculate both total energies and forces and thus to deal with structural relaxations. Both LDA+U versions yield coherent results concerning the energetical hierarchy for Fe3Al, i.e., a stabilization of the experimentally stabel DO3 structure against the Ll 2 structure at moderate values of U, although the details concerning absolute energy shifts, lattice constant, and magnetism differ. For Fe impurities in Al the AMF result resembles the local-spin-density approximation result of a vanishing magnetic moment through structural relaxations, whereas with the FLL functional the magnetic moment remains finite.