Ab Initio Calculations of Reactive Pathways for α-Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (α-HMX)

Abstract

Using the BLYP and B3LYP level of density functional theory, four possible decomposition reaction pathways of HMX in the gas phase were investigated: N-NO 2 bond dissociation, HONO elimination, C-N bond scission of the ring, and the concerted ring fission. The energetics of each of these four mechanisms are reported. Dissociation of the N-NO 2 bond is putatively the initial mechanism of nitramine decomposition in the gas phase. Our results find the dissociation energy of this mechanism to be 41.8 kcal/mol at the BLYP level and 40.5 kcal/mol at the B3LYP level, which is comparable to experimental results. Three other mechanisms are calculated and found at the BLYP level to be energetically competitive to the nitrogennitrogen bond dissociation; however, at the B3LYP level these three other mechanisms are energetically less favorable. It is proposed that the HONO elimination and C-N bond scission reaction of the ring would be favorable in the condensed phase.

Ab initio calculations of the effects of H+ and NH4+ on the initial decomposition of HMX

“…The B3LYP function with a moderate basis set (6-31G*) has been utilized to predict the thermal decomposition reactions of HMX [17,19]. In this study, complexes formed through the interaction of HMX with H + or NH 4 + and the transition states were optimized at the B3LYP/6-31G* level of theory.…”

“…The earlier calculation results have shown that the N-NO 2 bond rupture is putatively one of the most important initial reactions for the thermal decomposition of nitramine [19,[26][27][28]. Here, we first considered the N-NO 2 bond dissociation reactions for the HMX and the three complexes (PHMX1, PHMX2 and AHMX) as shown in Scheme 1.…”

“…Generally, b-HMX is considered as a model structure to study the thermal decomposition mechanisms that have been intensively studied by several research groups [17,18]. As for the initial decomposition mechanism of HMX, four different unimolecular reaction mechanisms have been proposed: NO 2 elimination, HONO elimination, concerted ring scission and dissociation of the ring along the C-N bond [19]. Among these mechanisms, N-NO 2 bond homolysis is putatively considered as the most important ''first reaction'' in the detonation of HMX [20,21].…”

Modeling the Reactions of Energetic Materials in the Condensed Phase

“…Several theoretical studies have also been reported on the energetics of gas-phase decomposition pathways for HE materials using a variety of methods. For example, we point to work in RDX and HMX where both quantum chemistry [44][45][46][47] and classical simulations of unimolecular dissociation 48,49 were used.…”

The Mechanism and Dynamics of Explosive Combustion in Aerosol Fuels

“…Liquid or solid state combustion and detonation processes have been the subject of considerable experimental (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) and theoretical (17)(18)(19)(20)(21)(22)(23)(24)(25) efforts. Yet, experimental methods for obtaining a detailed characterization of reaction intermediates and products in the condensed phase are limited and much less precise than in for instance the gas phase.…”