174
5 Vibrational Up-Pumping in Polymorphic Materials
Fig. 5.10 Overtone contributions to vibrational up-pumping in FOX-7 polymorphs. The overtones
are shown for (blue) N = 2 and (green) N = 3, and overlain by g(ω) (black). Plots are shown for
a α-FOX-7, b β-FOX-7 and c γ-FOX-7
The models point towards the sensitivity decrease being predominantly the result of
a decrease in max , given that the remaining g(ω) are largely unchanged, Fig. 5.8.
Hence, a new mechanism for the decreased sensitivity of layered materials is therefore proposed based on the decreased ability of these materials to up-pump vibrational energy. Without a larger dataset it is not yet possible to correlate the change
in predicted impact sensitivity to an absolute change in initiation energy. However,
based on the datasets in Chap. 4, it is predicted that γ-FOX-7 should be notably
less sensitive than the α-form. Thus this model suggests a major deficiency in the
current experimental approach to studying impact sensitivity of polymorphic materials. Furthermore, this demonstrates the importance of considering mechanicallyinduced structural transformations that may occur immediately before, or during,
initiation events.
5 Vibrational Up-Pumping in Polymorphic Materials
Fig. 5.10 Overtone contributions to vibrational up-pumping in FOX-7 polymorphs. The overtones
are shown for (blue) N = 2 and (green) N = 3, and overlain by g(ω) (black). Plots are shown for
a α-FOX-7, b β-FOX-7 and c γ-FOX-7
The models point towards the sensitivity decrease being predominantly the result of
a decrease in max , given that the remaining g(ω) are largely unchanged, Fig. 5.8.
Hence, a new mechanism for the decreased sensitivity of layered materials is therefore proposed based on the decreased ability of these materials to up-pump vibrational energy. Without a larger dataset it is not yet possible to correlate the change
in predicted impact sensitivity to an absolute change in initiation energy. However,
based on the datasets in Chap. 4, it is predicted that γ-FOX-7 should be notably
less sensitive than the α-form. Thus this model suggests a major deficiency in the
current experimental approach to studying impact sensitivity of polymorphic materials. Furthermore, this demonstrates the importance of considering mechanicallyinduced structural transformations that may occur immediately before, or during,
initiation events.