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Nitro Groups vs. N-Oxide Linkages: Effects Upon Some Key Determinants of Detonation Performance

Politzer P., Murray J. S.

Central European Journal of Energetic Materials

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2017

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Vol. 14, no. 1

3--25

EN

Increasing the nitrogen/carbon ratios in the molecular frameworks of C,H,N,O explosives has attracted considerable attention because it tends to result in more positive heats of formation and often greater densities. In conjunction with this, there has been a growing interest in N-oxide linkages, N+ → O−, as another source of oxygen in these compounds, in addition to or even possibly replacing NO2 groups. In this study, for a series of polyazines and polyazoles, we have compared the effects of introducing a single N-oxide linkage or NO2 group upon key properties that affect detonation velocity and detonation pressure. We found that: (1) The heats of formation per gram of compound, which is what is relevant for this purpose, are almost always higher for the N-oxides. (2) The nitro derivatives have greater densities and detonation heat releases. In relation to the latter, it must be kept in mind that increasing detonation heat release tends to be accompanied by increasing sensitivity. (3) The N-oxides produce more moles of gaseous detonation products per gram of compound.

2

Prediction of the Density of Energetic Materials on the Basis of their Molecular Structures

Rahimi R., Keshavarz M. H., Akbarzadeh A. R.

Central European Journal of Energetic Materials

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2016

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Vol. 13, no. 1

73--101

EN

The density of an energetic compound is an essential parameter for the assessment of its performance. A simple method based on quantitative structure-property relationship (QSPR) has been developed to give an accurate prediction of the crystal density of more than 170 polynitroarenes, polynitroheteroarenes, nitroaliphatics, nitrate esters and nitramines as important classes of energetic compounds, by suitable molecular descriptors. The evaluation techniques included cross-validation, validation through an external test set, and Y-randomization for multiple linear regression (MLR) and training state analysis for artificial neural network (ANN), and were used to illustrate the accuracy of the proposed models. The predicted MLR results are close to the experimental data for both the training and the test molecular sets, and for all of the molecular sets, but not as close as the ANN results. The ANN model was also used with 20 hidden neurons that gave good result. The results showed high quality for nonlinear modelling according to the squared regression coefficients for all of the training, validation and the test sets (R2 = 0.999, 0.914 and 0.931, respectively). The calculated results have also been compared with those from several of the best available predictive methods, and were found to give more reliable estimates.

3

Crystal Density Prediction, Charge Density Distribution and the Explosive Properties of the Highly Energetic Molecule 2-Methyl-5-nitramino-tetrazole: a DFT and AIM Study

Srinivasan P., Kumaradhas P.

Central European Journal of Energetic Materials

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2013

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Vol. 10, no. 1

53--68

EN

The ab initio crystal density, bond topological and explosive properties of the energetic molecule 2-methyl-5-nitraminotetrazole (MNAT) have been calculated by the MOLPAK/PMIN software and the AIM theory. The density predicted from the crystal structure simulation almost matches the experimental density. The geometrical parameters of the molecule lifted from the crystal structure are in very close agreement with the reported X-ray molecular structure. The bond topological analysis predicts a signifcantly low bond electron density, as well as a less Laplacian of electron density, for the N–NO2 bond. The Laplacian for the bond to the attached methyl group, the C(2)–N(2) bond, is also found to be less negative; the less negative values of the Laplacian confrms that these are the weakest bonds in the molecule. The impact sensitivity (h50) of the molecule has been calculated, and is almost equal to the reported experimental value. The sensitivity of the molecule was also estimated from the electrostatic imbalance parameter and has the value ν = 0.242. The isosurface of the electrostatic potential of the molecule displays a high negative electrostatic potential region around the tetrazole ring and the nitramine N–N bond, which are the possible reactive locations in the molecule.