Introducing Nitramide Group into High Energy Density Material Molecule Leads to Enhanced Performance
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1.
Beijing Institute of Technology
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2.
California Institute of Technology
Abstract
Although it has been verified by many experimental studies that the design of introducing nitrogen-rich groups into current molecular backbones is a practical method to increase the detonation properties, there is no clear understanding of how energetic explosophores would affect the energy storage density and energy release degree of high energy density materials (HEDMs). The BCHMX (cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole) molecule was designed based on the HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane) molecule by introducing intramolecular carbon–carbon linkages, which provides an excellent spot to introduce a nitramide group. Thus, we designed the BCHMX-ENO (2,4,6,8,9-pentanitro-2,4,6,8,9-pentaazabicyclo[3.3.1]nonane) molecule. To examine its properties, we first employed evolutionary algorithms USPEX to predict the crystal structure of BCHMX-ENO. Then, we applied QM-MD (quantum mechanics molecular dynamics) simulations to examine the initial thermal decomposition reactions and used a combination of RxMD (reactive molecular dynamics with ReaxFF force field) and QM-MD simulations to predict the detonation performance of BCHMX and BCHMX-ENO. We found that nitramide group influences initial reaction steps by affecting the molecular spatial distribution, bond length, and atom distance. We predicted that BCHMX-ENO shows improved detonation properties with 7.40% higher Chapman–Jouguet (CJ) pressure, 2.54% higher detonation velocity and 6.60% higher CJ temperature than BCHMX. This is because nitramide group introduction increases HEDM's nitrogen content and oxygen balance, leading to more CO2, N2 and fewer carbon clusters at the CJ state. After expansion to normal conditions from the CJ state, fewer CO gases were produced, indicating that BCHMX-ENO is more environmentally friendly than BCHMX. This study uncovers how the specific functional group influences the energetic properties of HEDMs from the atomic perspective, providing useful information for designing environmentally acceptable alternatives with improved properties.
Copyright and License
This publication is licensed under CC-BY 4.0 .
Supplemental Material
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacsau.5c00411.
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Ion distance matrices for different types of atoms (Table S1); CL-20/BCHMX-ENO structures predicted by USPEX with enthalpy/density/lattice parameters(Table S2 and S5); bond order cutoffs for chemical reactions (Table S3); optimization progress of BCHMX-ENO structures across iterations (Table S4); comparison of the CL-20 crystal structures predicted by USPEX and experimental data (Table S6); relative energy distribution of CL-20 structures from USPEX generations (Figure S1); lowest-energy BCHMX-ENO structures from 27 USPEX generations (Figure S2); time evolution of total energy per unit mass during cook-off simulations for BCHMX and BCHMX-ENO systems (Figure S3); and species analysis for β-HMX decomposition under heating (Figure S4) (PDF)
Contributions
CRediT: Yi Wang data curation, writing - original draft; Shichao Liu data curation, writing - review & editing; Wei Le software, validation; Wanjun Zhao software, validation; Dezhou Guo conceptualization, data curation, methodology, validation, visualization, writing - original draft, writing - review & editing.
Conflict of Interest
The authors declare no competing financial interest.
Acknowledgement
This work is supported by National Natural Science Foundation of China (U2430203), State Key Laboratory of Explosion Science and Safety Protection (QKKT25-01), and the US National Science Foundation (CBET 2311117).
Additional details
- National Natural Science Foundation of China
- U2430203
- Division of Chemical, Bioengineering, Environmental, and Transport Systems
- 2311117
- State Key Laboratory of Explosion Science and Safety Protection
- QKKT25-01
- Caltech groups
- Division of Chemistry and Chemical Engineering (CCE)
- Publication Status
- In Press