We present a formula for the calculation of K-edge resonant inelastic x-ray
scattering on transition metal compounds, based on a local interaction between
the valence shell electrons and the 1s core hole. Extending a previous
result, we include explicit momentum dependence and a basis with multiple
core-hole sites. We apply this formula to a single-layered charge, orbital and
spin ordered manganite, La0.5Sr1.5MnO4, and obtain good agreement
with experimental data, in particular with regards to the large variation of
the intensity with momentum. We find that the screening in
La0.5Sr1.5MnO4 is highly localized around the core-hole site and
demonstrate the potential of K-edge resonant inelastic x-ray scattering as a
probe of screening dynamics in materials