Study of relativistic effects on nuclear shieldings using density-functional theory and spin–orbit pseudopotentials

We combine a perturbational calculation, using spin–orbit pseudopotentials, of the spin–orbit effect on nuclear shieldings with scalar relativistic effects taken into account self-consistently using quasirelativistic pseudopotentials. The shieldings are calculated for light nuclei in systems containing heavy atoms, for which matching spin–orbit and quasirelativistic pseudopotentials are used. The second-order spin–orbit contribution arising from the magnetic field dependence of the one-electron spin–orbit Hamiltonian is also included. The method is implemented within the framework of density-functional theory and is capable of treating large molecular systems economically. Calculations are presented for the HX and CH3X (X=F, Cl, Br, I) molecules, third-row transition metal carbonyls, and a series of methyl mercury compounds.