Ground-state properties of Fe, Co, Ni, and their monoxides: Results of the generalized gradient approximation

The lattice parameter, bulk modulus, cohesive energy, and magnetization of Fe, Co, and Ni are calculated using the generalized gradient approximation (GGA) of Perdew and co-workers. The GGA results agree better with experimental data than the corresponding results calculated with the local-spin-density approximation (LSDA). In particular, the overestimation of the cohesive energies are reduced and the GGA correctly predicts the bcc ferromagnetic phase to be the ground state of Fe, while the LSDA fails to do so. We have also studied the electronic and magnetic properties of the insulating antiferromagnetic transition-metal compounds FeO, CoO, and NiO with the GGA. For these oxides it is found that the results are very similar to the results calculated with use of the LSDA.