Coupled Hartree-Fock calculations of magnetic properties of the benzene molecule: estimate of the Hartree-Fock limit for magnetic susceptibilities and nuclear shieldings

Five basis sets of gaussian functions have been developed to calculate magnetic properties of the benzene molecule within the framework of a coupled Hartree-Fock (CHF) approach exploiting the entire D6h symmetry. Separate contributions provided by k, sigma and pi-electrons have been evaluated in order to analyze the Pauling-London ring-current model. Our results are at variance with this classical model, as the contribution of k and sigma-electrons to the enhanced out-of-plane magnetic susceptibility is roughly 50% of the total value. In addition, k electrons provide a de-shielding of proton comparable with that of pi-electrons. The HF limits for electric dipole polarisability, magnetic susceptibility and magnetic shielding of hydrogen and carbon nuclei have been estimated.