Electronic and magnetic structure of KNiF3 perovskite.

The ground-state electronic structure of the ferromagnetic and antiferromagnetic phases of ${\mathrm{KNiF}}_{3}$ has been investigated using the ab initio periodic Hartree-Fock approach. The system is a wide-gap insulator. The antiferromagnetic phase is correctly predicted to be more stable than the ferromagnetic phase (0.031 eV per Ni pair at the experimental geometry). The energy difference between these phases is shown to obey a ${\mathit{d}}^{\mathrm{\ensuremath{-}}12}$ (d is the shortest Ni-Ni distance) power law, as suggested in the literature. The superexchange interaction turns out to be additive with respect to the number of Ni-Ni neighbors, as assumed in model spin Hamiltonians. Elastic properties, charge, and spin-density maps, and density of states plots are reported.