Energetic materials, structure crystallization

How readily this sequence of events will occur for any given compound (i.e. its sensitivity) depends of course upon its molecular structure and composition, as well as its crystal properties and physical form. Achieving greater insight into molecular factors offers a route to designing new less-sensitive energetic materials understanding crystal and... 

Structure 20 and salts 115 and 116 are formed by condensation of nitric oxide with diethylmalonate. Arulsamy and Bohle warn that this new type of compact ring structure forms dense crystals, and compounds 20, 115, and 116 are potential energetic materials which decompose violently at high temperatures <2002AGE2089>. 

Analyses of the structures and properties of a large number of energetic materials reveal that a combination of amino and nitro groups in a molecule often leads to better thermal stability, lower sensitivity to shock and impact, and increased explosive performance because of an increase in crystal density. Such observations are attributed to both intermolecular and intramolecular hydrogen bonding interactions between adjacent amino and nitro groups. Some modern triazole-based explosives have been designed and synthesized with this in mind. 

This chapter will not provide reviews of density and structure prediction, but rather focus on our work and its emphasis on predictions for energetic materials. Because of the importance of crystal density in the performance of energetic materials, our initial efforts were directed to this area in general and to volume additivity techniques in particular. 

Summary and Challenges. Because of the expense, labor, time requirements and possible danger (both to personnel and the environment) of synthesizing new energetic materials, it is important to pre-select only materials which have the potential for substantially better performance than compounds currently in use. In this chapter, our procedures for crystal structure (and density) prediction were detailed. Crystal structure prediction provides an entry into other important areas such as sensitivity and crystal habit. 

The high explosive octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazocine (HMX, Fig. 1) is the energetic material in a number of high performance military explosive and propellant formulations [3], HMX exhibits three crystal polymorphs at ambient pressure denoted J3- [4,5], a- [6], and <5-FlMX [7] and listed in terms of stability with increasing temperature. At temperature T 550 K the crystalline structure become unstable and HMX begins to melt. The liquid phase of HMX is very unstable and therefore no direct measurements of... 

Azide compounds of hypervalent main group elements such as Si and Ge are also highly explosive [83,84], but their structures and energetics have not been widely explored. Quite recently, the crystal structure of the Si(N3)62 anion has been reported, which has 90% nitrogen content, enough to be a possible high-energetic material candidate[83,84]. It is noted that Si(N3)62 (E = Ge, Pb) have been synthesized and are structurally known [83],... 

The structure of high energetic materials - nitroazo(azoxy)furazans showing high crystal density and excellent energetic properties of detonation velocity and detonation pressure - has been studied by NMR spectroscopy [137, 139, 505, 508, 509, 511, 518, 519],... 

Oyumi, Y, Brill, T. B. and Rheingold, A. L. (1986a). Thermal decomposition of energetic materials. 9. Polymorphism, crystal structures, and thermal decomposition of polynitroazabicyclo [3.3.1]nonanes. J. Phys. Chem., 90,2526-33. [286]... 

Choi CS (1977) The crystal structures. In Fair HD, Walker RF (eds) Energetic materials. V 1 Physics and chemistry of the inorganic azides. Plenum Press, New York, Chapters, pp 97—130... 

The first, and earliest, application of CSP was to aid in crystal structure determination of an nncharacterized material, combined with experimental observations that, on their own, are insufficient to provide a structure. The idea is that CSP calculations can provide a set of plausible, energetically feasible structures that could be used as starting models to refine against experimental data. Under the assumption that the set of predicted structures is complete, and sufficiently accurate that the experimental... 

Oyumi, Y., Brill, T.B. and Rheingold, A.L. (1986) Thermal Decomposition of Energetic Materials 9. Polymorphism, Crystal Structures and the Thermal Decomposition of Polynitroazabicyclo [3.3.1Jnonanes Journal of Physical Chemistry 90, 2526-2533. 

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