Energy transfer rates and impact sensitivities of two classes nitramine explosives molecules

Some explosives are stable molecules with large energy barriers to chemical reaction, and in shock or impact initiation, a sizable amount of phonon energy must be converted to the molecular internal higher vibrations by multiphonon up pumping. To investigate the relationship between impact sensitivities and energy transfer rates, the number of doorway modes of explosive molecules is estimated by a simple theory in which the rate is proportional to the number of normal mode vibrations. We evaluated frequencies of normal mode vibrations of 13 explosive molecules which are CHNO nitramine-contained and have not been analyzed previously. The number of doorway modes in the regions of 200–700 cm⁻¹ was evaluated by the direct counting method. For more clear investigation of the relationship we have classified these 13 nitramine explosive molecules, by the number of nitramine group they contained, into two groups. There are eight molecules that contained one nitramine group and five molecules that contained poly-nitramine groups. It is found that the number of doorway modes shows a linearly correlation to the impact sensitivities derived from drop hammer tests. This result is in agreement with that of several previous works. Besides, it is also noted in our study that in those nitramine explosives molecules with similar molecular structure (similar number nitramine group they contained) and similar molecular weight, the correlation between the sensitivity and the number of doorway modes is higher. We found that the vibrational frequency of ω corresponds to nitro group motions of every molecule is contributed to the number of doorway modes in the regions of 200–700 cm⁻¹.