The role of Hartree-Fock exchange in the simulation of X-ray absorption spectra: A study of photoexcited [Fe(bpy)3]2+

We present a theoretical analysis for the K- and L-2/3-edge static and picosecond X-ray absorption spectra of [Fe(bpy)(3)](2+). Simulations of the pre-edge region at the Fe K-edge using time-dependent density functional theory demonstrate the importance of Hartree-Fock exchange within the exchange-correlation functional, especially when describing charge transfer and 1s -> 3d transitions. This becomes particularly relevant for range separated functionals, for which the incorporation of Hartree-Fock exchange at short range decreases the absolute error in the excitation energy usually observed using TD-DFT. Finally, we compute and interpret the L-2/3-edge spectrum using the Restricted Open-Shell Configuration Interaction Singles method. (C) 2013 Elsevier B.V. All rights reserved.