Magnetism with Generalized-Gradient-Approximation Density Functionals

We report generalized-gradient-approximation (GGA) density-functional studies of Cr, V, and Pd, using an all-electron, general-potential linearized-augmented-plane-wave technique. These calculations were undertaken in order to assess the utility of the GGA as an improvement over the local-density approximation in describing transition-metal magnetism. It is found that although the tendency towards magnetism is enhanced, both V and Pd are correctly predicted to be nonmagnetic with the recent GGA functional of Perdew (PW GGA-II) as with the Langreth-Mehl-Hu (LM) functional. Calculations for commensurate antiferromagnetic Cr show that the PW GGA-II predicts an overly large moment of 1.4μ_B while the LM functional yields a moment of 0.88 μ_B, which is also larger than experiment. Furthermore the PW GGA-II yields a large magnetic energy for Cr which is difficult to reconcile with the observed spin-density-wave ground state.