Electric nuclear shielding tensors by finite-field methods
Using Hartree–Fock SCF wavefunctions, the linear and quadratic electric nuclear shielding tensors for the diatomic molecules H2, N2, CO and HF have been calculated by a finite-field method. These tensors have also been computed from equations relating them to dipole moment and polarizability derivatives. The two methods give reasonable agreement depending on the quality of the basis set used. A study of the basis set dependence of the computed components ϕHx, xz and ϕFx, xz of the shielding tensor for HF, giving the electric field at the H and F nuclei in the x direction perpendicular to the internuclear axis and proportional to the product FxFz of the electric field strengths applied parallel and perpendicular to the axis, revealed that large basis sets are apparently necessary for reasonable accuracy.