Scalar and spin-dependent relativistic effects on magnetic properties   calculated with four-component methods: the nuclear magnetic resonance   parameters of the lead halides
  The results of calculations of nuclear magnetic resonance (NMR) parameters for the lead halides is reported in this paper. The results are obtained by using four-component methods. The use of the nonrelativistic L\'evy-Leblond Hamiltonian along with the relativistic Dirac-Coulomb and spin-free ones allows us to discriminate scalar and spin-dependent effects on the parameters. It is found that the wide range of the lead NMR spectra and their large anisotropies are, mainly, due to spin-dependent effects on the paramagnetic term. Among the relativistic scalar corrections, the so-called spin-Zeeman kinetic-energy term turns out to be dominant. The reduced spin-spin coupling constants become proportional to the product of the atomic numbers of the coupled nuclei. 
Rodolfo H. Romero