The frontier molecular orbital (FMO) characteristics are closely related to the overall electronic delocalization and aromaticity of cyclic molecules. We calculated some FMOs, including all occupied π orbitals, of benzene, carborazine, and borazine, and plotted their energy level maps in Figure . Carborazine does not have triple rotation axes like benzene and borazine, which makes it not have double-degenerate highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) like the latter two. The HOMO-LUMO gap of carborazine is obviously smaller than that of benzene and borazine, so its chemical stability may be relatively low, and its electrons should show greater softness and are more polarizable. delocalization of carborazine and borazine is definitely weaker than that of benzene. As for which of the latter two has stronger delocalization characteristics, it can be determined by examining the contribution of each element to their occupied π orbitals.