Theoretical Studies on the Performance of HMX with Different Energetic Groups

Multi-aspect and comprehensive atomic insight: the whole process of thermolysis of HMX/Poly-NIMMO-based plastic bonded explosive

Based on the reactive molecular dynamics, the whole process of thermolysis of HMX/Poly-NIMMO-based PBX was studied in detail at the micro scale, which provided a novel atomic insight into the thermolysis mechanism of HMX/Poly-NIMMO. Further, it was compared with the HMX single substance system to explore the influence of binder on thermolysis of HMX. According to the findings, the activation energy required by pyrolysis of HMX in the mixed system is much less than that required by the pure HMX system at both phases. From the point of view of reaction energy, poly-NIMMO promoted the thermolysis of HMX. Especially, the mechanism analysis confirmed this point. The nitro and hydroxyl groups detached from Poly-NIMMO will react with HMX, and the generated HNO2 will further accelerate the decomposition process of nitrogen heterocycles. In addition, the number of the final products H2O and H2 in the two-component system increased greatly, but the number of CO2 and N2 molecules had not changed much, and C clusters were formed in the system. The evolution trend of bond number further verified the above analysis. While the maximum cluster number does drop with increasing temperature at first, after a particular temperature threshold is reached, it remains unchanged. In a nutshell, poly-NIMMO will hasten HMX's thermolysis and reduce the system's stability when subjected to heat.

Synthesis and Antioxidant Studies of 2,4-Dioxothiazolidine-5-acetic Acid Based Organic Salts: SC-XRD and DFT Approach

In the current study, two organic salts (1 and 2) are synthesized, and then crystalline structures are characterized by FTIR, UV spectroscopy, and X-ray crystallographic studies. The organic salts 1 and 2 are optimized at the M06/6-311G(d,p)level of theory and further utilized for analysis of natural bond orbitals (NBOs), natural population, frontier molecular orbitals (FMOs), and global reactivity parameters, which confirmed the stability of the studied compounds and charge transfer phenomenon in the studied compounds. The studies further revealed that 1 and 2 are more stable than 3. The lowest energy merged monomer-coformer conformations were docked as flexible ligands with rigid fungal proteins and DNA receptors. The stagnant binding of the monomer through two H bonds with protein was observed for ligands 1 and 3 while different pattern was found with 2. The coformers formed a single H bond with the active site in 2 and 3 and a single pi-arene H interaction in 1. The two-point ligand-receptor interactions hooked the monomer between DNA base pairs for partial intercalation; pi stacking with additive hydrogen bonding with the base pair led to a strong benzimidazole interaction in 1 and 2, whereas ethylene diamine formed weak H bonding. Thus, the molecular docking predicted that the coformer exhibited DNA intercalation reinforced by its salt formation with benzimidazole 1 and methyl benzimidazole 2. Antioxidant studies depicted that 3 has a higher IC50 value than that of 2,4-D and also the largest value among the studied compounds, whereas 2 showed the lowest value among the studied compounds.

Multi-aspect simulation insight on thermolysis mechanism and interaction of NTO/HMX-based plastic-bonded explosives: a new conception of the mixed explosive model

Reactive molecular dynamics (RMDs) calculations were used to determine, for the first time, the process of thermolysis of the mixed explosives, including 3-nitro-1,2,4-triazol-5-one (NTO) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazoline (HMX). Significantly, this is the first time that a layered model for mixed explosives, which is an extreme innovation of mixed explosive models was adopted. It is shown that a large amount of NO2 in the HMX and OH groups generated by the decomposition of HNO2 has a favorable effect on the thermolysis of NTO, as further validated by a reduction in the activation energy of NTO/HMX. The amount of H2O and N2 in the resulting products increased significantly, but the amount of NH3 changed slightly. The analysis results correspond to the change in chemical bonds. Whenever there is an increase in temperature, the time for the maximum number of clusters to appear is shortened accordingly. In addition, the acidity of NTO has been considered. An independent gradient model based on Hirshfeld partition (IGMH) and atoms in molecule (AIM) analysis of NTO/HMX was implemented. The relatively strong hydrogen bonds indicate that HMX can inhibit the acidity of NTO and is beneficial for the wide application of NTO/HMX-based plastic-bonded explosives (PBXs).

Theoretical insight into different energetic groups on the performance of energetic materials 2,5,7,9-tetranitro-2,5,7,9-tetraazabicyclo[4,3,0]nonane-8-one

CONTEXT

Energetic materials are a class of materials containing explosive groups or containing oxidants and combustibles. The optimization of energetic materials has a significant impact on the development of industry and national defense. For high-energy density compounds (HEDC) that have not been synthesized or are dangerous to experimental operation, it is of guiding significance to predict its energy level, physicochemical properties, and safety through molecular design and theoretical calculation. Cyclic urea nitramine series compounds are a type of energetic compounds with high density and excellent detonation performance. In this study, 2,5,7,9-tetranitro-2,5,7,9-tetraazabicyclo[4,3,0]nonane-8-one (K-56) was used as the parent structure, and 36 energetic derivatives were designed. The effects of introducing single and multiple substituents on the electronic structure, energy gap, heat of formation, detonation performance, thermal stability, thermodynamic parameters, and surface electrostatic potential of K-56 and its derivatives were discussed in detail. The results exhibit the following: (1) the single substitution of -C(NO₂)₃ (A6) can reduce the detonation velocity of K-56 by 11.9 % and the detonation pressure by 19.8 %, while the double substitution of -C(NO₂)₃ (B6) can increase the density of K-56 by 11.6 %, the detonation velocity by 10.9 %, and the detonation pressure by 31 %. (2) The heat of formation of K-56 (-110.0 kJ mol^-1) increased by 324.18 % and 628.81 %, respectively, proving that -N₃ is an extremely effective group to improve HOF. (3) The thermal stability of the derivatives generated by the monosubstitution of the target group on the six-membered ring is better than that of the parent compound.

METHODS

Gaussian16 and Multiwfn 3.8 packages are the software for calculation. In this study, the parent structure K-56 and its derivatives were optimized at the B3LYP/6-311G (d,p) level to obtain the zero point energy and thermal correction data of all compounds. Then the vibration analysis of the optimized structure is carried out to confirm that its configuration is stable. Then the M06-2X-D3/def2-TZVPP basis set is used to calculate the single point energy.

Molecular design and theoretical study of oxadiazole-bifurazan derivatives

CONTEXT

The design and synthesis of new high energy density materials is an important part of the research in the field of high energy materials. However, the synthesis of high-energy materials is very difficult and dangerous. Therefore, it is necessary to design the compounds in advance and evaluate the performance of the designed compounds, so as to screen the high-energy candidate compounds with excellent performance and provide reference for future synthesis and application. 1,2,5-oxadiazole (furazan) and 1,2,4-oxadiazole are five-membered nitrogen-oxygen heterocycles. Because their structures contain high-energy N-O, C=N bonds, they can effectively improve the energy density and oxygen balance of compounds, which has attracted widespread attention. In this paper, 42 kinds of oxadiazole-bifurazan energetic derivatives were designed by inserting different functional groups and changing the parent bridging groups with 1,2,4-oxadiazole and furazan as the basic structural units. Their electronic structures, aromaticity, heats of formation (HOFs), detonation properties, thermodynamic properties and electrostatic potential were systematically studied by density functional than theory (DFT). The results show that -C (NO₂)₃ has the greatest improvement effect on HOFs among all the substituent groups. The detonation performance of -N=N- bridged oxadiazole-bifurazan derivatives is better than that of -NH-NH- bridged derivatives. And -C(NO₂)₃ is the most effective group to improve the detonation performance and density of compounds. Compared with the parent compounds, when a -C(NO₂)₃ was introduced, the density increased by about 5.5%. A6 (D = 10.30 km·s^-1, P = 48.86 GPa) and D6 (D = 9.57 km·s^-1, P = 42.31 GPa) are the compounds with the best D and P among the designed compounds, which are higher than RDX and HMX, and are potential candidates for new high-energy materials.

METHODS

With the help of Gaussian16 software and Multiwfn 3.8 package, the B3LYP method in density functional theory was selected. The 6-311G (d, p) basis set was used to optimize the structure of the 42 derivatives, and the high-precision def2-TZVPP basis set was used to calculate the energy.

Theoretical studies of novel high energy density materials based on oxadiazoles

In this study, 32 energetic compounds were designed using oxadiazoles (1,2,5-oxadiazole, 1,3,4-oxadiazole) as the parent by inserting different groups as well as changing the bridge between the parent. These compounds had high density and excellent detonation properties. The electrostatic potentials of the designed compounds were analyzed using density functional theory (DFT). The structure, heat of formation (HOF), density, detonation performances (detonation pressure P, detonation velocity D, detonation heat Q), and thermal stability of each compound were systematically studied based on molecular dynamics. The results showed that the -N₃ group has the greatest improvement in HOF. For the detonation performances, the directly linked -N=N- and -NH-NH- were beneficial when used as a bridge between 1,2,5-oxadiazole and 1,3,4-oxadiazole, and it can also be found that bridge changing had little effect on the trend of detonation performance, while energetic groups changing influenced differently. In general, the introduction of nitro groups contributes to the improvement of the detonation performance of the compounds. In this study, the compounds containing the highest amount of nitro groups were found to have better detonation performance than their counterparts and were not significantly different from RDX and HMX.