Improved approach to spin-polarized relativistic LMTO formalism: Application to the electronic structure of Fe-Ni compounds at the Earth’s core conditions

Abstract

A first-principles fully relativistic spin-polarized linear muffin-tin orbital method for calculations of electronic structure of magnetic crystals that contain heavy elements is presented. The orbital contribution to the four-current density is omitted, and no further approximation is made to treat the spin polarization and the spin-orbit coupling effects in solving the Dirac equation for a spin-dependent potential. The self-consistent band structure and calculated spin and orbital magnetic moments for Fe metal are compared with previous calculations and with experimental data. First-principles non-spin-polarized calculations of the ground state of some ordered Fe-Ni alloys at the Earth's core pressure for several concentrations of Fe are presented. In the density-of-states function of the nonmagnetic ${\mathrm{FeNi}}_{3}$ a pronounced peak in the vicinity of the Fermi level has been observed. A spin-polarized calculation for ${\mathrm{FeNi}}_{3}$ has been performed, which predicts a weak ferromagnetism of $0.393{\ensuremath{\mu}}_{B}/\mathrm{cell}.$ The effect is explained in terms of the electronic structure. An attempt is made to roughly estimate the Curie temperature for this compound.