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

When stimulated, for example, by a high temperature, the physical and chemical properties of energetic materials (EMs) may change, and, in turn, their overall performance is affected. Therefore, thermal stability is crucial for EMs, especially the thermal dynamic behavior. In the past decade, significant efforts have been made to study the thermal dynamic behavior of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF), one of the new high-energy-density materials (HEDMs). However, the thermal decomposition mechanism of DNTF is still not specific or comprehensive. In this study, the self-consistent-charge density-functional tight-binding method was combined with molecular dynamics (MD) simulations to reveal the differences in the thermal decomposition of DNTF under four heating conditions. The O–N (O) bond would fracture first during DNTF initial thermal decomposition at medium and low temperatures, thus triggering the cracking of the whole structure. At 2000 and 2500 K, NO 2 loss on outer ring I is the fastest initial thermal decomposition pathway, and it determines that the decomposition mechanism is different from that of a medium-low temperature. NO 2 is found to be the most active intermediate product; large molecular fragments, such as C 2 N 2 O, are found for the first time. Hopefully, these results could provide some insights into the decomposition mechanism of new HEDMs.

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“…The similar situation also appeared in the studies of thermal decomposition of a similar structure to DNTF. 47 , 48 …”

Section: Resultsmentioning

confidence: 99%

Molecular Dynamics Simulations of the Thermal Decomposition of 3,4-Bis(3-nitrofurazan-4-yl)furoxan

et al. 2021

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“…Furthermore, the revealed mechanism can provide a hand to the design of new energetic materials [23,24]. Therefore, unimolecular results represent a reasonable approximation to the primary, initial behavior for the decomposition of energetic molecules in general condensed phase materials [25].…”

Section: Introductionmentioning

confidence: 99%

Initial Mechanisms for the Unimolecular Thermal Decomposition of 2,6-Diamino-3,5-dinitropyrazine-1-oxide

et al. 2018

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The initial channels of thermal decomposition mechanism of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) molecule were investigated. The results of quantum chemical calculations revealed four candidates involved in the reaction pathway, including the C–NO2 bond homolysis, nitro–nitrite rearrangement followed by NO elimination, and H transfer from amino to acyl O and to nitro O with the subsequent OH or HONO elimination, respectively. In view of the further kinetic analysis and ab initio molecular dynamics simulations, the C–NO2 bond homolysis was suggested to be the dominant step that triggered the decomposition of LLM-105 at temperatures above 580 K. Below this temperature, two types of H transfer were considered as the primary reactions, which have advantages including lower barrier and high rate compared to the C–NO2 bond dissociation. It could be affirmed that these two types of H transfer are reversible processes, which could buffer against external thermal stimulation. Therefore, the excellent thermal stability of LLM-105, that is nearly identical to that of 1,3,5-triamino-2,4,6-trinitrobenzene, can be attributed to the reversibility of H transfers at relatively low temperatures. However, subsequent OH or HONO elimination reactions occur with difficulty because of their slow rates and extra energy barriers. Although nitro–nitrite rearrangement is theoretically feasible, its rate constant is too small to be observed. This study facilitates the understanding of the essence of thermal stability and detailed decomposition mechanism of LLM-105.

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“…The presence of nitro groups significantly changes the photochemical and photophysical behavior of molecules and affect the stability and sensitivity of energetic molecules [ 4 , 5 , 6 ]. Recent literature shows [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ] excited energetic molecules deactivated from the S 1 excited state to the S 0 ground state through a conical intersection (CI). Experimental and theoretical studies by Bernstein and coworkers [ 6 ] found that the conical intersection plays an important role in the non-adiabatic decay of the energetic molecule dimethylnitramine (DMNA).…”

Section: Introductionmentioning

confidence: 99%

“…This isomerization process was predicted to take place through a “loose transition state-like geometry”. Bernstein’s group studied the non-adiabatic transitions of many energetic molecules [ 8 , 9 , 10 , 11 , 12 , 13 , 14 ] and found that their (S 1 /S 0 ) CI are similar in structure. Soto, Arenas and collaborators [ 15 , 16 , 17 ] used the complete active space with second-order perturbation theory (CASPT2) to predict NO 2 –ONO isomerization in nitramide molecules through a (S 1 /S 0 ) CI ; a similar CI structure in the nitromethane molecule has led to the nitro elimination reaction.…”

Section: Introductionmentioning

confidence: 99%

A Photophysical Deactivation Channel of Laser-Excited TATB Based on Semiclassical Dynamics Simulation and TD-DFT Calculation

et al. 2018

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A deactivation channel for laser-excited 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) was studied by semiclassical dynamics. Results indicate that the excited state resulting from an electronic transition from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular mrbital (LUMO) is deactivated via pyramidalization of the activated N atom in a nitro group, with a lifetime of 2.4 ps. An approximately 0.5-electron transfer from the aromatic ring to the activated nitro group led to a significant increase of the C–NO2 bond length, which suggests that C–NO2 bond breaking could be a trigger for an explosive reaction. The time-dependent density functional theory (TD-DFT) method was used to calculate the energies of the ground and S1 excited states for each configuration in the simulated trajectory. The S1←S0 energy gap at the instance of non-adiabatic decay was found to be 0.096 eV, suggesting that the decay geometry is close to the conical intersection.

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

Cited by 15 publications

References 46 publications

Molecular Dynamics Simulations of the Thermal Decomposition of 3,4-Bis(3-nitrofurazan-4-yl)furoxan

Molecular Dynamics Simulations of the Thermal Decomposition of 3,4-Bis(3-nitrofurazan-4-yl)furoxan

Initial Mechanisms for the Unimolecular Thermal Decomposition of 2,6-Diamino-3,5-dinitropyrazine-1-oxide

A Photophysical Deactivation Channel of Laser-Excited TATB Based on Semiclassical Dynamics Simulation and TD-DFT Calculation

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