Bethe-Salpeter equation calculations of resonant inelastic x-ray scattering at the nitrogen K edge

We present theoretical calculations of resonant inelastic x-ray scattering (RIXS) at the nitrogen K edge of several materials along with direct comparison to experimental results. Our approach is based on a Bethe-Salpeter equation formalism, and our calculations are carried out using an extension of the \textsc{ocean} package,\footnote{J. Vinson, E. L. Shirley, J. J. Rehr, and J. J. Kas, Phys. Rev. B {\bf 83}, 115106 (2011) } including both intermediate and final-state excitonic effects. By building upon a DFT basis we include ground-state effects without system-dependent fitting parameters. We are able to account for the general trends and features seen in experiment. A more \textit{ad hoc} account of other contributions to the measured spectra, primarily phonon coupling, is attempted, but this highlights some current shortcomings limiting fully \textit{ab initio} calculations of the near-edge x-ray spectra of extended systems.