The Structural Investigation of Energetic Materials

Structure determination in the context of this chapter means the determination of the atomic arrangements in materials in the crystalline state. There are a number of aspects to structural analyses. They may be used to identify substances since they can be performed without previous knowledge of chemical composition. It is possible to determine from structural analyses the connectedness, conformation, configuration (or absolute configuration under special experimental circumstances), packing, solvent interactions, and average thermal motion associated with the substances of interest. With careful experimentation in properly chosen cases, electron density distributions can also be evaluated. 

One consequence of the extensive research activity in structural anafy-sis has been the development of a computerized X-ray crystal structure 

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There have been a number of investigations involving the study of nitroolefins as useful intermediates in the synthesis of energetic materials. A characteristic of many of them is a large twist about the double bond. Interest in the structural characteristics that accompany the rotation motivates a discussion of details. As would be expected, the rotation out of the normal planar conformation is associated with spatial crowding. Rgure 14 illustrates some of the largest out-of-plane rotations that have been measured and, in one case, calculated for crowded ethylenes [25j. 

From among the different classes of compounds considered in this work, most of the computational work was done on amines, while less examples are found for nitro compounds and very few for nitroso ones. The different studies may be classified into several major areas (1) conformational analysis and structural investigation (2) spectroscopic experiments and study of chemical effects (3) investigation of chemical reactions mechanism (4) heats of formation and density calculations, especially of high energetic materials. In the following sections we will concentrate on molecular mechanics based research studies, or on such where molecular mechanics calculations played a... 

Although the possible catalytic applications of PILCs is the subject more extensively studied, large efforts have also been devoted to the characterisation of the microporous structure of these materials. To this end, the application of both classical and novel models based on gas adsorption has been reported in the literature. The adsorption data depend on the internal physical and chemical structure of the solid and on the nature of the adsorbate molecule. Thus, the adsorption results contain information about structural and energetic properties of the materials surface [8]. In the following, the methods considered in this work to investigate the microporous properties of several alumina-pillared saponites are briefly presented. 

An important step towards accurate descriptions of solid ionic energetic materials has been done by Sorescu and Thompson.[104-106] They used DFT and the pseudopotential method to investigate the structural and electronic properties of AND [104, 105] and AN [106] in solid phases. The advantage of using the pseudopotential approximation is that only the valence... 

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