Quadratic response calculations of the electronic spin-orbit contribution to nuclear shielding tensors

Abstract

The electronic spin-orbit contribution to nuclear magnetic shielding tensors, which causes the heavy-atom chemical shift of the shielding of light nuclei in the vicinity of heavy elements, is calculated as a sum of analytical quadratic response functions. We include both the one- and two-electron parts of the spin-orbit Hamiltonian and consider the interaction with both the Fermi contact and the spin-dipolar mechanisms. Ab initio calculations at the SCF and MCSCF levels are presented for the H1 and C13 shielding tensors in the hydrogen and methyl halides. The applicability of different approximations to the full spin-orbit correction is discussed, and the calculated results are compared with experimental data, where available.

Formal relations connecting different approaches to calculate relativistic effects on molecular magnetic properties

“…8,17,21,22 As a consequence, relativistic effects on magnetic properties within the Breit-Pauli approximation can be expressed as first-, second-, and third-order RSPT corrections to the Schrödinger molecular energy.…”

Relativistic effects on the nuclear magnetic shielding tensor

“…In the last few years an ever increasing number of new formalisms and calculations for the evaluation of relativistic effects on molecular properties from four-, two-, or onecomponent response schemes or perturbation theory approaches have been published. [1][2][3][4][5][6][7][8][9][10][11] It was shown that the inclusion of such effects in the calculation of some molecular properties is mandatory when one wants to reproduce experimental trends. 4,10 Relativistic spin-orbit ͑SO͒ effects on magnetic molecular properties were thought to be the most important ones until recent calculations of Visscher et al 4 Numerical results for nuclear magnetic shieldings obtained by four-component calculations and their counterpart from RayleighSchrödinger perturbation theory ͑RSPT͒ only match each other for the shielding of heavy atoms X in HX compounds when a new term different from SO is included.…”

Perturbational and ECP Calculation of Relativistic Effects in NMR Shielding and Spin–Spin Coupling

“…The contribution of the full (one-and two-electron) field-free SO operator differs only by a few percent from the results obtained with the one-electron SO operator only, for heavy nuclei [36,37]. The computationally very efficient, one-electron/onecenter mean-field approximation to the one-and two-electron SO operator [38] using the AMFI software [39], has been adopted for these calculations [37].…”

“…Such "fully perturbational" studies have been carried out in Refs. [7,26,35,36,40,42,45,46] for r and in Refs. [16,43,44] for J, at various ab initio levels.…”