NICS is a popular method for quantitatively characterizing aromaticity by measuring the shielding effect of an acted external magnetic field at or near center of a ring. It has been confirmed that the normal component of the magnetic shielding tensor at 1 Å above the center of a ring, denoted as NICS(1)zz, can robustly reflect its aromatic characteristics. We calculated the total NICS(1)zz values for the three isoelectronic species as well as the contributions of the π electrons and the other electrons (core + σ electrons), respectively, which are listed in Table . The total NICS(1)zz of -31.0 ppm for benzene demonstrates its strong aromaticity, which is in accordance with common knowledge of chemistry. The total NICS(1)zz of carborazine is -23.1 ppm, indicating that carborazine is also clearly aromatic, but to a lesser extent than benzene; in contrast, the corresponding value for borazine is -5.21 ppm, a fairly small negative value indicating that it is a weakly aromatic species. The NICS(1)zz values of the isoelectronic analogues studied are in good agreement with those in previous calculations. As is evident from the contributions of the different kinds of electrons to the NICS(1)zz, the magnetic shielding at 1 Å above the center of the three isoelectronic rings almost exclusively from their π electrons, while the contribution of the rest of the electrons (core + σ electrons) can be neglected, which suggests that there is no detectable global delocalization of  electrons in the studied systems, and only  aromaticity is reflected by the NICS(1)zz data. a The values obtained from Ref. are given in brackets.