Paramagnetic resonance hyperfine structure of hexachloroprotactinate(IV)

Dirac scattered-wave calculations are presented for the PaCl62- cluster that models the Pa4+ impurity site in the octahedral Cs2ZrCl6 lattice. The calculations predict a Γ7u ground state, and show fairly good agreement with the observed g tensor, Pa231 hyperfine interactions, and crystal-field splittings. The Zeeman and Pa231 hyperfine interactions are isotropic, arising from the large orbital contributions to the magnetic moment of the ground Kramers doublet. The amount of covalency is predicted to be about 3%, and the largest contribution to covalency comes from the chlorine 3d5/2 spinors (∼2%).