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6 General Conclusions and Future Directions
predicting sensitivity properties, one could in principle design an IM in silico, with
a full assessment of its sensitivity properties, without ever needing to set foot in the
laboratory until a promising candidate was found.
The vibrational up-pumping model developed in this thesis is one such model. It
was demonstrated to be capable of predicting the relative sensitivity ordering of a
broad range of EMs based on knowledge of the crystal structure. In its current form,
this model makes it possible to predict the sensitivity of materials which may be difficult to obtain in large quantities. High-pressure phases are of particular note. During
a detonation, immense pressures are experienced at the shock front, which are well
above the pressures typically required to induce structural phase transitions in organic
EMs [9–11]. The reactivity of a material to mechanical perturbation may therefore
change during detonation. Thus, understanding the relative sensitivity of pressurerelated polymorphs may prove crucial for understanding the detonation properties of
polymorphic EMs. An excellent example of this is RDX, which undergoes numerous
high-pressure phase transitions [11–13]. In other cases, new polymorphic forms may
crystallise under pressure [14], and thus it may not be possible to easily prepare large
quantities for testing. The model developed in this thesis can therefore be applied to
predict the sensitivity of a new phase, and make judgement as to whether purification of this phase should be pursued further. Alternatively, polymorphic phases may
appear as non-isolable impurities within a powder. If this impurity acts to sensitise
the mixture (e.g. δ-HMX impurities in β-HMX samples [15]) additional work must
be done to remove it. Hence, the up-pumping model offers a means to new validation methods for material composition. Finally, as demonstrated in this thesis, the
experimental impact sensitivity testing of polymorphic materials can prove very challenging, and perhaps impossible in some cases. The up-pumping model can therefore
be used in parallel with experimental results to assist in their interpretation.
A particularly promising application of the model developed in this thesis is in
parallel with crystal structure prediction. It is now possible to predict the potential
crystal structures of complex organic molecules to a good degree of accuracy [16].
The combination of crystal structure prediction with sensitivity prediction truly offers
the way to a new paradigm in EM research. New molecules could be completely
designed in silico, their crystal structures predicted, and the up-pumping model
applied to generate a list of sensitivities. In doing so, the work in this thesis would
open the door to a complete restructuring of the way EM research is performed. As
further developments are made on the up-pumping model (e.g. inclusion of electronic
effects, vibrational response to pressure, defects, etc.), its performance will surely
improve. As it does, the reality of making in silico EM design a reality becomes
closer.
6 General Conclusions and Future Directions
predicting sensitivity properties, one could in principle design an IM in silico, with
a full assessment of its sensitivity properties, without ever needing to set foot in the
laboratory until a promising candidate was found.
The vibrational up-pumping model developed in this thesis is one such model. It
was demonstrated to be capable of predicting the relative sensitivity ordering of a
broad range of EMs based on knowledge of the crystal structure. In its current form,
this model makes it possible to predict the sensitivity of materials which may be difficult to obtain in large quantities. High-pressure phases are of particular note. During
a detonation, immense pressures are experienced at the shock front, which are well
above the pressures typically required to induce structural phase transitions in organic
EMs [9–11]. The reactivity of a material to mechanical perturbation may therefore
change during detonation. Thus, understanding the relative sensitivity of pressurerelated polymorphs may prove crucial for understanding the detonation properties of
polymorphic EMs. An excellent example of this is RDX, which undergoes numerous
high-pressure phase transitions [11–13]. In other cases, new polymorphic forms may
crystallise under pressure [14], and thus it may not be possible to easily prepare large
quantities for testing. The model developed in this thesis can therefore be applied to
predict the sensitivity of a new phase, and make judgement as to whether purification of this phase should be pursued further. Alternatively, polymorphic phases may
appear as non-isolable impurities within a powder. If this impurity acts to sensitise
the mixture (e.g. δ-HMX impurities in β-HMX samples [15]) additional work must
be done to remove it. Hence, the up-pumping model offers a means to new validation methods for material composition. Finally, as demonstrated in this thesis, the
experimental impact sensitivity testing of polymorphic materials can prove very challenging, and perhaps impossible in some cases. The up-pumping model can therefore
be used in parallel with experimental results to assist in their interpretation.
A particularly promising application of the model developed in this thesis is in
parallel with crystal structure prediction. It is now possible to predict the potential
crystal structures of complex organic molecules to a good degree of accuracy [16].
The combination of crystal structure prediction with sensitivity prediction truly offers
the way to a new paradigm in EM research. New molecules could be completely
designed in silico, their crystal structures predicted, and the up-pumping model
applied to generate a list of sensitivities. In doing so, the work in this thesis would
open the door to a complete restructuring of the way EM research is performed. As
further developments are made on the up-pumping model (e.g. inclusion of electronic
effects, vibrational response to pressure, defects, etc.), its performance will surely
improve. As it does, the reality of making in silico EM design a reality becomes
closer.