Theoretical Design of Green Energetic Materials: Predicting Stability, Detection, Synthesis and Performance

Abstract

Kohn-Sham density functional theory (KS-DFT) is today the standard quantum chemical method for the optimization of molecular geometries and calculation of vibrational frequencies. It is generally used to probe potential energy surfaces and characterize transition states. The widely used B3LYP exchange-correlation functional has also been quite successful for energetic molecules and their reactions. In general, B3LYP geometries are more accurate than energies. However, there are examples of nitro-group rich systems where B3LYP produces both erroneous geometries and energies, and for some of these the more recent M06-2X functional [5] of Truhlar and coworkers performs considerably better. A general observation is that when the two functionals give geometries in consensus, these can be trusted for energy calculations at higher level. Double zeta basis sets augmented by Theoretical Design of Green Energetic Materials 17

Initial mechanisms for the unimolecular decomposition of electronically excited bisfuroxan based energetic materials

“…11,12 A particularly essential application of this latter fundamental detail concerning energetic materials is for the design of new energetic species and chemical classes. 13,14 This molecular approach emphasizes isolated energetic molecule behavior as the central first step in the energy release processes in either gas or condensed phase. [13][14][15][16] The assumed methodology can be justified by the local nature of the molecular excitation processes that occur upon even gentle shock wave excitation in any organic molecular solid, as discussed below.…”

“…13,14 This molecular approach emphasizes isolated energetic molecule behavior as the central first step in the energy release processes in either gas or condensed phase. [13][14][15][16] The assumed methodology can be justified by the local nature of the molecular excitation processes that occur upon even gentle shock wave excitation in any organic molecular solid, as discussed below. Thus, focus of the present effort is the decomposition of isolated, electronically excited, energetic molecules, diamino-bisfuroxans A and B, both experimentally and theoretically.…”

“…The initial decomposition product molecule or species is observed and characterized, and decomposition mechanisms are calculated for a single energetic species theoretically: this approach to the elucidation of reaction kinetics/dynamics/mechanism has been pursued for many decades. [11][12][13][14][15][16][17] In general, the difference between condensed phase and gas phase reactions is that solid state reactions occur within the rigid constraining environment of a crystal lattice, in which intermolecular interactions can influence reaction mechanisms and directions. 18 Other important factors that can affect the solid reactions include the presence of solvates, planar defects, phase transitions, disorder, and even crystal morphology.…”

“…15,19 Certain types of molecular bonds are particularly susceptible to rupture by the input of hot spot energy and these are readily identified and elucidated by the present isolated, single molecule strategies. [13][14][15] In our studies, we have followed decomposition mechanisms for various classes of energetic materials initiated from excited electronic states. Based on the centuries old observations of triboluminescence, one readily concludes that molecular electronic excitation must contribute to the initial chemical reactions that begin the release of stored molecular energy for an energetic system.…”

“…The capacity of computational chemistry to assist in the design, characterization, and evaluation of compounds of real practical importance has greatly increased during the past ten years. 13,14,18 In the present report, energy resolved spectra of the initial product molecule NO, fragmented from electronically excited bisfuroxans, are studied to define the decomposition kinetics and dynamics of the energetic material isolated molecules. These spectra facilitate the characterization of the decomposition processes through elucidation of the rotational and vibrational temperatures of the ground electronic state NO product.…”