The nucleus-independent chemical shift (NICS) of benzene is calculated using a one-dimensional ring model. In a real compound, an individual feature contributes to the NICS and it makes an intuitive understanding of the NICS complicate and difficult. We can avoid this complexity by using an extremely simple model. To overcome a classical and naive understanding such as the Fleming's left hand rule or the Ampère's circuital law, we apply the Schrödinger equation to an electron on a one-dimensional ring, and evaluate the NICS quantitatively in a framework of this ring model, using both Ramsey's equation and Pople's method. We also compare these results with the ab-initio MO calculations. From these results, we discuss about the diamagnetic and paramagnetic terms (diatropic- and paratropic-type currents) of NICS.
