Optical and magnetic properties of the 5f1AnX6q− series: A theoretical study

The ground and first excited states of PaX(6)(2-) (X=F,Cl,Br,I), UX(6)(-) (X=F,Cl,Br) and NpF(6) are calculated using the spin-orbit complete active space perturbation theory at second order method and the g-factors are deduced. The isotropic g-matrix is built from first principles, and the g-factors are found to be negative. Results are analyzed in the frame of crystal field theory. It is shown that it is more appropriate to consider the spin-orbit coupling before the crystal field interaction and that g-factors are principally governed by the metal-ligand distance. The complexes of the series with the longest bond length, even with a high covalent character, exhibit g-factors close to the free ion value.