Electronic structure and resonant inelastic x-ray scattering in osmates. I. Perovskite NaOsO3

We have investigated the electronic and magnetic properties of the perovskite ${\mathrm{NaOsO}}₃$ within density functional theory using the generalized gradient approximation while taking into account strong Coulomb correlations in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. ${\mathrm{NaOsO}}₃$ is a G-type AFM Mott insulator which is characterized by AFM spins canted away from the $c$ axis. This magnetic configuration explains the weak ferromagnetism in ${\mathrm{NaOsO}}₃$. Despite the large strength of spin-orbit coupling, it has only a small effect on the electronic and magnetic properties of ${\mathrm{NaOsO}}₃$. We have also investigated theoretically the resonant inelastic x-ray scattering (RIXS) spectrum at the Os ${L}₃$ edge. The experimentally measured RIXS spectrum of ${\mathrm{NaOsO}}₃$ in addition to the elastic scattering peak at 0 eV possesses a sharp feature below 2 eV corresponding to transitions within the Os ${t}_2g$ levels, a strong intense peak at around 2.8 eV which is from ${t}_2g\ensuremath{\rightarrow}{e}_g$ transitions, and a wide structure stretching from 6 eV to 12 eV that corresponds to ligand-to-metal charge transfer excitations, d-d transitions to Os ${t}_2g$ and ${e}_g$ manifolds from the Os 5${d}_{\mathrm{O}}$ states derived from the ``tails'' of oxygen 2$p$ states.