Multiconfiguration Pair-Density Functional Theory for Vertical Excitation Energies in Actinide Molecules

Abstract

Modeling actinides with electronic structure theories is challenging because these systems present a strong ligand field and metal–ligand covalency. We systematically investigate the effectiveness of pair-density functional theory (PDFT) for the calculation of vertical excitation energies in An­(III), [AnIIICl6]3–, and [AnVIO2]2+ (An = U, Np, Pu, and Am). We compare the performance of PDFT, hybrid PDFT, and multistate PDFT with traditional active-space methods followed by perturbation theory, like multistate CASPT2, and with experimental data. Overall, multistate PDFT gives quantitative agreement with multistate CASPT2 at a significantly reduced computational cost.