The DFT-B3LPY method, with basis set 6-31G*, is employed to calculate the structures and properties for aromatic explosives containing -NO 2 groups, nitro derivatives of benzene and nitro derivatives of aminobenzene. It is found that there is a parallel relationship between experimental impact sensitivity and bond order of the weakest C-NO 2 bond in a molecule in each series. Previously, based on semiempirical MO calculations, "the principle of the smallest bond order (PSBO) " has been proposed by us to identify the relative magnitudes of impact sensitivity of a series of explosive compounds with similar molecular structures. Here, PSBO is verified powerfully from the ab initio calculations for title compounds.
