Electron binding energy of uranium-ligand and uranyl-ligand anions*

Electron binding energies of the early actinide element uranium in gas-phase anion complexes are calculated by relativistic density functional theory (DFT) with two different exchange-correlation functions (RPBE and B3LYP) and also in the Hartree-Fock (HF) approximation\footnote{ADF2010.02, SCM.com}. Scalar and spin-orbit calculations are performed, and the calculated energies are compared to available experimental measurements and shown to disagree by energies of order 1 eV. Strong correlations that are poorly treated in DFT and HF can be included by a hybrid approach in which a generalized Anderson impurity model is numerically diagonalized. Reduction-oxidation (redox) potentials of aqueous actinide ions show improved agreement with measured values in the hybrid approach\footnote{S. E. Horowitz and J. B. Marston, J. Chem. Phys {\bf 134} 064510 (2011).}. We test whether or not similar improvements are found in the gas-phase.