Gradient-corrected ab initio calculations of spin-spiral states in fcc-Fe and the effects of the atomic-spheres approximation

The total energy of noncollinear spin-spiral states in bulk fcc-Fe is calculated using the linear-muffin-tin-orbital (LMTO) method in the atomic-spheres approximation (ASA). The relative stabilities of the spin-spiral states obtained with the gradient-corrected exchange-correlation functional PW91 differs from those of the local-spin-density approximation, but the discrepancy with experimental data remains. To analyze the accuracy of the LMTO-ASA, full-potential calculations using the linear-augmented-plane-wave method are also performed. The difference in magnetization energy between the methods is found to be comparable to the energy difference between the lowest-energy spin-spiral state and the lowest-energy collinear state, which is the antiferromagnetic state.