Polymorphism of high energy materials

Although personally I am quite content with existing explosives, I feel we must not stand in the path of improvement... (Churchill 1950) 

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Regarding the polymorphism of colourants, another feature common to them and high energy materials (Chapter 9) is that much of the information may be found in sources of limited accessibility, in the case of colourants in company records, or in old or not widely circulated literature. 

Just as HMX is one of the oldest and widely used high energy materials, HNIW (also sometimes referred to as CL-20) is one of the newest cyclic nitramines and has generated considerable interest, although the early work is in references of limited accessibility (see for instance, references l-A in both Russell et al. 1992, 1993, and Sorescu et al. 1998a, and references 1-7 therein). These same authors agree that five polymorphs are known, although Nedelko et al. (2000) indicate the existence of six crystal moditications. 

Very small differences in bond strength between different silica polymorphs were found. Since the Extended Huckel Method is too approximate to calculate reliably the small diffferences in energy between low-density material, containing micropores, and high-density material without micropores, work was initiated to study the same problem but now with two rigorous techniques that are currently considered to be state of the art. 

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