Exploring perturbative density-functional-based approaches for simulating resonant-inelastic x-ray scattering maps in transition-metal complexes

Resonant inelastic x-ray scattering (RIXS) is a two-photon process that provides valuable information on the electronic structure of molecules and materials that, due to selection rule restrictions, is not easily accessible by one-photon spectroscopies. With the continuing development of light source technologies, RIXS is rapidly becoming an important technique for the study of gas- and solution-phase molecular systems, and the need for reliable yet inexpensive electronic structure methods to aid in the prediction and interpretation of complicated spectral features is becoming apparent. In this talk, I will present simplified approaches based on linear-response time-dependent density functional theory and perturbative treatments of excited-state transition moments and spin-orbit couplings. I will demonstrate that an approach based on linear-response time-dependent density functional theory and the zeroth-order regular approximation, is able to describe the RIXS maps of ruthenium complexes with sufficiently good accuracy without the need to solve expensive quadratic-response or fully relativistic equations.