Density-functional study of (formula presented) LSDA versus GGA

Abstract

The local-spin-density approximation and the generalized-gradient approximation (GGA) are used to perform density-functional total-energy calculations at zero temperature for (formula presented) in the ordered (formula presented) and (formula presented) structures. Our calculations show that commonly used GGA functionals fail to predict the experimentally stable (formula presented) 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. © 2002 The American Physical Society.