CleaRIXS: A fast and accurate first-principles method for simulation and analysis of resonant inelastic x-ray scattering

Resonant inelastic x-ray scattering (RIXS), which probes the occupied and unoccupied electronic subspaces in an interrelated way, is one of the most information-rich experimental techniques employed in the investigation of electronic structure. By combining two diverse and established approaches to modeling electronic excited states (namely the response-based approach and the constrained-occupation approach), we introduce an ab initio, accurate, and efficient computational framework for simulation and analysis of RIXS spectra for electronic transitions. The core-hole linear-response RIXS (CleaRIXS) [1] method not only ensures accurate incorporation of the interaction of electrons with core and valence holes, but also automatically maps the salient RIXS features to the relevant electronic transitions. Through comparison with previous methanol C K-edge RIXS measurements, we show the efficacy of the formalism in modeling different regions of the RIXS spectrum and in gaining physical insight about their origins. The importance of including the electron-hole interactions outside the core region is explored, in addition to the connection between CleaRIXS and determinant-based methods for simulating x-ray absorption and nonresonant x-ray emission. CleaRIXS provides a robust and extendable framework for prediction and interpretation of RIXS processes and for the simulation of complex electronic excited states in general.

[1] S. Roychoudhury, D. Prendergast, Phys Rev B.106.115115 (2022)