PNNL

Abstract

Prediction of X-ray absorption near edge spectra of transition metal complexes have important and broad application areas in chemistry and biology. In this letter, we have investigated the predictive ability of multiconfiguration pair-density functional theory (MC-PDFT) for the computation of X-ray absorption pre-edge and near-edge spec- tra at the K-edge of a near-complete series of hydrated first-row transition metal ions with d -orbital occupancy from d ² to d ?. We compare our results with those obtained with time-dependent density functional theory (TDDFT) and restricted active-space second-order perturbation theory (RASPT2). While the results obtained with TDDFT are accurate for spectra that are dominated by single excitations, RASPT2 and MC- PDFT can correctly distinguish between singly and doubly or higher-order excited states with quantitative accuracy compared with experiment. Core-level spectroscopy with RASPT2 is accurate, but can be computationally very expensive and may encounter convergence issues. Our results show that MC-PDFT performs equally well for all hydrated transition metal ions with significantly less computational cost and without any convergence issues.