Theoretical studies of the actinides: method calibration for the UO22+ andPuO22+ ions

As part of method assessment for the theoretical study of actinide systems, we have performed I-component relativisric pseudopotential calculations fo r the uranyl and plutonyl ions. The calculated spectroscopic constants comp are well with fully relativisric 4-component results at both the Hartree-Fo ck and correlated levels of theory. We deduce that second-order spin-orbit effects in these systems are minor and show that the 1-component method cho sen (B3LYP in particular) gives reliable results at low computational cost. The ground state of the plutonyl ion has been determined as H-3(6). (C) 19 99 Elsevier Science B.V. All rights reserved.