Electronic structure of tetrafluoro- and tetraoxo-actinide complexes

Fully relativistic self-consistent calculations are reported for AcF4 and (UO4)Q complexes, where Ac = Th, U, Np, Pu, using Dirac–Slater local density theory. Energy levels are compared with available photoelectron spectra; the character of low-lying optical transitions is discussed. Using numerical free ion orbitals as a variational basis, we discuss bonding mechanisms and the degree of Ac 5f-ligand 2p covalency. Additional 5f character is found to be distributed across the ligand valence band, in contrast to crystal field models.