Full-potential generalized gradient approximation calculations of spiral spin-density waves in γ-Fe

Abstract

Using two different forms of the generalized gradient approximation (GGA) for exchange and correlation, we have performed ab initio full-potential calculations of spiral spin-density waves in \ensuremath{\gamma}-Fe for wave vectors $\mathbf{q}=(2\ensuremath{\pi}/a)(0,0,\ensuremath{\alpha})$ and $\mathbf{q}=(2\ensuremath{\pi}/a)(\ensuremath{\gamma},0,1).$ We conclude that whereas the local spin-density approximation is merely missing gradient corrections, the GGA contains gradient terms which, although a great improvement in most cases, are inherently incorrect when applied to spiral spin-density waves.