Topology of magnetic-field induced current-density field in diatropic mono-cyclic molecules

Concise information on the general features of the quantum-mechanical current density induced in the electrons of a molecule by a spatially uniform, time-independent magnetic field is obtained via a stagnation graph that shows the isolated singularities and the lines at which the current-density vector field vanishes. Stagnation graphs provide compact description of current-density vector fields and help the interpretation of molecular magnetic response, e.g., magnetic susceptibility and nuclear magnetic shielding. The stagnation graph of six cyclic, planar aromatic molecules has been obtained at the Hartree-Fock level via a procedure based on continuous transformation of the origin of the current density formally annihilating the diamagnetic contribution. Some common distinctive elements observed for cyclic aromatic rings CnHn, with n=3,4, . . . ,8, in the presence of a magnetic field normal to the molecular plane, are discussed. The results can be used for a general discussion of diatropism in aromatic systems.