Self-interaction artifacts on structural features of uranyl monohydroxide from Kohn–Sham calculations

Invoking a DFT + U approach, we explored self-interaction artifacts in results from Kohn–Sham (KS) density functional calculations on the geometry and the vibrational frequencies of uranyl monohydroxide and the corresponding tetra-aqua complex. Exchange–correlation functionals based on the local density approximation (LDA) and the generalized-gradient approximation (GGA) predict equilibrium geometries for [UO2(OH)]+ that deviate from the results of hybrid DFT calculations and high-level wavefunction-based methods such as CCSD(T). LDA + U and GGA + U functionals with corrections for the insufficient localization of the U 5f shell yield better agreement, in particular for the angle U-Oh-H. At the LDA level, a linear coordination of the OH ligand results; with the +U correction, the angle U-Oh-H is reduced by ~35°, in good agreement with CCSD(T) results. At the GGA level, the bending angle is changed by ~20°. This relatively strong self-interaction artifact is traced back to a spurious π interaction between U 5f and O(p) orbitals which is less pronounced in the presence of further (aqua) ligands.