Calculation of nuclear magnetic shieldings XIV. Relativistic mass—velocity corrected perturbation Hamiltonians

A two-component relativistic SCF perturbation theory, based on the Douglas—Kroll—Hess (DKH) transformation, has been applied to the calculation of nuclear magnetic shielding tensors of hydrogen halides, HX (X = F, Cl, Br, I). Calculations were performed via the unrestricted coupled Hartree—Fock (CHF) scheme using gauge-including atomic orbitals (GIAOs) at four different levels. In the level I calculation, both the scalar relativistic (SR) and spin—orbit (SO) interactions were included in the zero-order Hamiltonian. However, the magnetic pertubation Hamiltonians were treated non-relativistically. The results of these calculations indicated a large interplay between the SR and SO interactions. The level I calculation was found to be insufficient to explain the full relativistic effect on the halogen atom shieldings. In order to reproduce the full relativistic effect, the mass-velocity effect on the magnetic perturbation Hamiltonians was introduced in the levels II—IV calculations. Inclusion of the mass-velo...