AB-INITIO STUDIES OF THE ELECTRONIC-STRUCTURE OF UF6, UF6+, AND UF-6 USING RELATIVISTIC EFFECTIVE CORE POTENTIALS

Ab initio calculations are performed on the electronic states of UF 6, UF6+, and UF6- using a relativistic effective core potential (ECP) for uranium and a nonrelativistic ECP for fluorine. In most of the calculations 56 valence electrons are treated explicitly using a contracted [3s3p2d2f/2s2p] Gaussian basis. Various ECP's were explored, but all yield an overall charge density of U+2.4 (F -0.4)6. The bonding in the ground state of UF6 is discussed. SCF and CI calculations on UF6+ are compared with the experimental photoelectron spectrum and with previous scattered-wave calculations. The role of spin-orbit coupling in the states of UF 6+ and UF6- is discussed. The calculated electron affinity of UF6 (7.1 eV) is considerably larger than current experimental estimates, but the relative energies of the states of UF6- are in excellent agreement (0.1-0.2 eV) with experiment. © 1979 American Institute of Physics.