  We present a computational study of resonant inelastic x-ray scattering
(RIXS) and x-ray absorption in a representative rare-earth nickelate LuNiO$_3$.
We study the changes in the spectra across the
metal-insulator/site-disproportionation transition. In particular, we address
the question of site-selectivity of the two methods in the disproportionated
insulating phase and the signature of metal-insulator transition in the
fluorescence-like feature of the RIXS spectra. To this end we use the local
density approximation + dynamical mean-field theory (LDA+DMFT) approach
combined with configuration integration method to compute the core-level
spectra.
