FIXED-SPIN-MOMENT CALCULATIONS ON BCC AND FCC IRON USING THE GENERALIZED GRADIENT APPROXIMATION

I have used the linear-muffin-tin-orbitals method and the fixed-spin-moment procedure to study stable and metastable ferromagnetic states of bcc and fcc iron. In particular, the influence of gradient corrections to the density functional is discussed. In accordance with previous results, the global minimum in the magnetovolume energy dependence of bcc iron occurs at too small lattice parameters in local-spin-density-approximation (LSDA) calculations and at too high magnetizations in generalized-gradient-approximation (GGA) calculations. For fcc iron, the LSDA and the GGA both predict the existence of two ferromagnetic states corresponding to a low-spin and a high-spin solution. However, the LSDA energetically favors a nonmagnetic state while the GGA yields a global energy minimum corresponding to the high-spin ferromagnetic state.