Relativistic energy levels and bonding in actinide hexaflourides

Abstract

A fully relativistic self-consistent Dirac–Slater model has been used to calculate one-electron energy levels and charge distributions for UF6, NpF6, and PuF6. Analysis of ground state charge densities reveals 5fn populations similar to free atom states; we are able to distinguish between metal–ligand bonding levels and the optically active levels described by crystal field theory. Ultraviolet and optical excitations, as well as ionziation energies, are calculated using an approximate transition state procedure and found to be in reasonable agreement with experiment. The Coulomb correlation integral appearing in the determination of the nature of 5f orbitals in solids is discussed on the basis of the systematics observed in our transition state calculations.