Density-functional study of Fe₃Al: LSDA versus GGA

The local-spin-density approximation and the generalized-gradient approximation (GGA) are used to perform density-functional total-energy calculations at zero temperature for Fe₃Al in the ordered D0₃ and L1₂ structures. Our calculations show that commonly used GGA functionals fail to predict the experimentally stable D0₃ structure as the one with the lower total energy. This qualitative discrepancy with experiment is attributed to an overestimation of the magnetic energy in GGA. The calculations were carried out using the mixed-basis pseudopotential (MBPP) method in the frozen-core approximation and the full-potential linearized-augmented-plane-wave (FLAPW) method, both with and without spin polarization. Although there are small differences in the magnitudes of the magnetic moments and the magnetic energies obtained with MBPP and FLAPW, both methods yield the same qualitative result.