Calculation of the fourth-rank nuclear magnetic hypershielding of some small molecules

A computational scheme has been implemented to evaluate magnetic hypershielding at the nuclei of amolecule in the presence of an external spatially uniform, time-independent magnetic field, accounting forcubic response contributions via Rayleigh-Schrödinger perturbation theory. Numerical estimates have beenobtained for hydrogen and heavier atoms in H2, HF, H2O, NH3, and CH4 molecules at the coupled Hartree-Fock level of accuracy within the conventional common-origin approach. Gaugeless basis sets of increasingsize and flexibility have been employed in a numerical test, to estimate the degree of convergence of theoreticaltensor components. A further test for convergence has been carried out by evaluating properties for twodifferent coordinate systems.