Molecular dynamics (MD) study to predict performances of a novel hexanitrohexaazaisowurtzitane/1,4-dinitroimidazole (CL-20/1,4-DNI) energetic cocrystal under different temperatures.

CONTEXT: To estimate the influence of temperature on properties of 2,4,6,8,10,12-hexanitro- 2,4,6,8,10,12-hexaazaisowurtzitane/1,4-dinitroimidazole (CL-20/1,4-DNI) cocrystal explosive, the supercell crystal of CL-20/1,4-DNI cocrystal model was established. The mechanical properties, sensitivity, and stability of cocrystal model under different temperatures (T = 225 K, 250 K, 275 K, 300 K, 325 K, 350 K) were predicted. Results show that mechanical parameters, including bulk modulus, tensile modulus and shear modulus are the lowest when temperature is 300 K, while Cauchy pressure is the highest, indicating that CL-20/1,4-DNI cocrystal model has better mechanical properties at 300 K. Cohesive energy density (CED) and its components energies decrease monotonically with the increase of temperature, illustrating that the CL-20 and 1,4-DNI molecules are activated and the safety of cocrystal explosive is worsened with the increase of temperature. Cocrystal model has relatively higher binding energy when the temperature is 300 K, implying that the CL-20/1,4-DNI cocrystal explosive is more stable under this condition. METHODS: The CL-20/1,4-DNI cocrystal model was optimized and the properties were predicted through molecular dynamics (MD) method. The MD simulation was performed with COMPASS force field and the ensemble was set as NPT, external pressure was set as 0.0001 GPa.

Theoretical Prediction on Properties of 3,4-Bisnitrofurazanfuroxan (DNTF) Crystal and its Polymer Bonded Explosives (PBXs) Through Molecular Dynamics (MD) Simulation.

CONTEXT: 3,4-Bisnitrofurazanfuroxan (DNTF) is a typical high energy density compound (HEDC), it has high crystal density and detonation parameters, but also high mechanical sensitivity. To decrease its mechanical sensitivity, the DNTF based polymer bonded explosives (PBXs) was designed. The pure DNTF crystal and PBXs models were established. The stability, sensitivity, detonation performance and mechanical properties of DNTF crystal and PBXs models were predicted. Results show that PBXs models containing fluorine rubber (F2311) and fluorine resin (F2314) have higher binding energy, meaning that DNTF/F2311 and DNTF/F2314 is relatively more stable. PBXs models have higher value of cohesive energy density (CED) than pure DNTF crystal, DNTF/F2311 and DNTF/F2314 have the highest value of CED, implying that the sensitivity of PBXs is effectively decreased, DNTF/F2311 and DNTF/F2314 is more insensitive. PBXs have lower crystal density and detonation parameters than DNTF, the energy density is declined, DNTF/F2314 has higher energetic performance than other PBXs. Compared with pure DNTF crystal, engineering moduli (tensile modulus, shear modulus, bulk modulus) of PBXs models are obviously decreased, but Cauchy pressure is increased, implying that the mechanical properties of PBXs is superior to pure DNTF component, the PBXs containing F2311 or F2314 have more preferable mechanical properties. Consequently, DNTF/F2311 and DNTF/F2314 have the best comprehensive properties and is more attractive among the designed PBXs, indicating that F2311 and F2314 are more advantageous and promising in ameliorating properties of DNTF. METHODS: The properties of DNTF crystal and PBXs models were predicted through molecular dynamics (MD) method under Materials Studio 7.0 package. The MD simulation was performed with isothermal-constant volume (NVT) ensemble, and the force field was chosen as COMPASS force field. The temperature was set as 295 K, the time step was 1 fs and the total MD simulation time was 2 ns.

Designing and property prediction of a novel three-component CL-20/HMX/TNAD energetic cocrystal explosive by MD method.

CONTEXT: Cocrystallization technology can effectively regulate crystal structure, alter packing mode, and improve physicochemical performances of energetic materials at molecule level. CL-20/HMX cocrystal explosive has high energy density than HMX, but it also exhibits high mechanical sensitivity. To decrease the sensitivity and improve the properties of CL-20/HMX energetic cocrystal, the three-component energetic cocrystal CL-20/HMX/TNAD was designed. The properties of CL-20, CL-20/HMX, and CL-20/HMX/TNAD cocrystal models were predicted. The results show that CL-20/HMX/TNAD cocrystal models have better mechanical properties than CL-20/HMX cocrystal model, implying that the mechanical properties can be effectively improved. The binding energy of CL-20/HMX/TNAD cocrystal models is higher than CL-20/HMX cocrystal model, indicating that the three-component energetic cocrystal is more stable, and the cocrystal model with the ratio 3:4:1 is predicted to be the most stable phase. CL-20/HMX/TNAD cocrystal models have higher value of trigger bond energy than pure CL-20 and CL-20/HMX cocrystal models, meaning that the three-component energetic cocrystal is more insensitive. The crystal density and detonation parameters of CL-20/HMX and CL-20/HMX/TNAD cocrystal models are lower than CL-20, illustrating that the energy density is declined. The CL-20/HMX/TNAD cocrystal has higher energy density than RDX and can be regarded as a potential high energy explosive. METHODS: This paper was performed with molecular dynamics (MD) method with the software of Materials Studio 7.0 under COMPASS force field. The MD simulation was performed under isothermal-isobaric (NPT) ensemble, the temperature and pressure was 295 K and 0.0001 GPa, respectively.

Theoretical research on performances of CL-20/HMX cocrystal explosive and its based polymer bonded explosives (PBXs) by molecular dynamics method.

In this article, the CL-20/HMX cocrystal model was established and its based polymer bonded explosives (PBXs) were designed. The static performances, including mechanical properties, stability and detonation performance of CL-20/HMX cocrystal model and PBXs models, were predicted by molecular dynamics (MD) method. The mechanical parameters, binding energy, and detonation parameters of PBXs models were calculated and compared with that of pure CL-20/HMX cocrystal model. The influence of polymer binders on performances of CL-20/HMX cocrystal explosive was evaluated. Results show that the polymer binders make the engineering moduli (tensile modulus, shear modulus, and bulk modulus) of PBXs declined and Cauchy pressure increased, meaning that the polymer binder can obviously improve mechanical properties of CL-20/HMX cocrystal explosive, and the PBXs model with fluorine rubber (F2311) has the best mechanical properties. In different PBXs models, the binding energy between CL-20, HMX molecules and F2311 is higher than other polymer binders, indicating that the CL-20/HMX/F2311 model is more stable. The PBXs models have lower value of crystal density and detonation parameters compared with pure CL-20/HMX cocrystal and the energetic performance of PBXs is weakened. The PBXs model with fluorine resin (F2314) has the highest energetic performance and it is higher than pure HMX. Therefore, the CL-20/HMX/F2311 and CL-20/HMX/F2314 models have more favorable comprehensive properties, proving that F2311 and F2314 are more preferable and promising to design CL-20/HMX cocrystal based PBXs.

Theoretical investigations on stability, sensitivity, energetic performance, and mechanical properties of CL-20/TNAD cocrystal explosive by molecular dynamics method.

The crystal models of trans-1,4,5,8-tetranitro-1,4,5,8-tetraazadecalin (TNAD), hexanitrohexaazaisowurtzitane (CL-20), and CL-20/TNAD cocrystal explosive with different component ratios were established. Molecular dynamics (MD) method was applied to predict the stability, sensitivity, energetic properties, and mechanical properties. The effect of component ratio on properties of CL-20/TNAD cocrystal explosive was investigated and estimated. Results show that the cocrystal model with component ratio in 1:1 exhibits the highest binding energy and it is more stable. In CL-20/TNAD cocrystal explosive, the interaction energy of trigger bond is increased by 0.8 ~ 15.0 kJ/mol, implying that the mechanical sensitivity of CL-20/TNAD cocrystal explosive is lower than CL-20 and the safety is effectively improved. Compared with raw CL-20, the crystal density of cocrystal explosive is declined by 0.014 ~ 0.193 g/cm3, detonation velocity is declined by 39 ~ 755 m/s, and detonation pressure is declined by 0.95 ~ 11.40 GPa; namely the energy density of CL-20/TNAD cocrystal explosive is lower than CL-20. The cocrystal explosives with component ratio in 10:1 ~ 1:1 still exhibit desirable detonation performance and can be regarded as high energy density explosives. The values of tensile modulus, shear modulus, and bulk modulus of CL-20/TNAD cocrystal explosive are decreased by 0.448 ~ 10.285 GPa, 0.195 ~ 4.189 GPa, and 0.194 ~ 6.292 GPa, respectively, Cauchy pressure is increased by 0.990 ~ 5.704 GPa, meaning that the rigidity, fracture strength, and hardness of cocrystal explosive are declined, while the plastic property and ductility are increased and the mechanical properties are improved. The cocrystal model with component ratio in 1:1 has the best mechanical properties. Consequently, the CL-20/TNAD cocrystal explosive with component ratio in 1:1 is more stable and insensitive; it also has high energy density and the best mechanical properties and may be an attractive candidate for high energy explosives.

Molecular dynamics research on effect of doping defects on properties of PETN.

To investigate the effect of doping defects on properties of pentaerythritol tetranitrate (PETN), the "perfect" and doping defective crystal models of PETN containing pentaerythritol (PE), pentaerythritol mononitrate (PEMonoN), pentaerythritol dinitrate (PEDiN), and pentaerythritol trinitrate (PETRIN) were established, respectively. Molecular dynamics (MD) method was applied to perform simulations, and sensitivity, detonation performance, and mechanical properties were calculated and compared. The results indicate that compared with PETN (1 1 0) supercell model, the interaction energy of trigger bond and cohesive energy density of the doped defect models decreased by 2.21~12.43 kJ mol-1 and 0.0219~0.0421 kJ cm-3, respectively, indicating that the sensitivity of defective models increases and the safety decreases. The density, detonation velocity, and detonation pressure of the doped defect model decreased by 0.018~0.061 g cm-3, 77.833~272.809 m s-1, and 0.746~2.544 GPa, respectively, and the oxygen balance is declined, indicating that the energy density of PETN decreased and the power decreased. Doped defects also cause the elastic modulus, bulk modulus, and shear modulus of PETN to decrease by 0.75~2.16 GPa, 0.44~0.89 GPa, and 0.30~0.89 GPa, respectively. The ratio of bulk modulus to shear modulus and Cauchy pressure increased by 0.05~0.28 GPa and 0.09~1.13 GPa, respectively, indicating that the deformation resistance, fracture strength, and hardness of the doped defect model decrease, stiffness decreases, and flexibility and ductility increase.

Theoretical investigations on structures, stability, energetic performance, sensitivity, and mechanical properties of CL-20/TNT/HMX cocrystal explosives by molecular dynamics simulation.

In this article, the CL-20, TNT, HMX, CL-20/TNT, CL-20/HMX and different CL-20/TNT/HMX cocrystal models were established. Molecular dynamics method was selected to optimize the structures, predict the stability, sensitivity, energetic performance, and mechanical properties of cocrystal models. The binding energy, trigger bond length, trigger bond energy, cohesive energy density, detonation parameters, and mechanical properties of each crystal model were obtained. The influences of co-crystallization and molar ratios on performances of cocrystal explosives were investigated and evaluated. The results show that the CL-20/TNT/HMX cocrystal explosive with a molar ratio of 3:1:2 or 3:1:3 had larger binding energy and better stability, i.e., CL-20/TNT/HMX cocrystal explosive was more likely to be formed with these molar ratios. The cocrystal explosive had shorter maximal trigger bond length, but larger trigger bond energy and cohesive energy density than CL-20, namely, the cocrystal explosive had lower mechanical sensitivity and better safety than CL-20 and the safety of cocrystal model was effectively improved. The cocrystal model with a molar ratio of 3:1:2 had the best safety. The energetic performance of the cocrystal explosive with a molar ratio of 3:1:1, 3:1:2, or 3:1:3 was the best. These CL-20/TNT/HMX cocrystal models exhibited better and more desirable mechanical properties. In a word, the cocrystal model with molar ratio of 3:1:2 exhibited the most superior properties and was a novel and potential high-energy-density compound. This paper could provide practical helpful guidance and theoretical support to better understand co-crystallization mechanisms and design novel energetic cocrystal explosives.

Theoretical investigations on the structures and properties of CL-20/TNT cocrystal and its defective models by molecular dynamics simulation.

"Perfect" and defective models of CL-20/TNT cocrystal explosive were established. Molecular dynamics methods were introduced to determine the structures and predict the comprehensive performances, including stabilities, sensitivity, energy density and mechanical properties, of the different models. The influences of crystal defects on the properties of these explosives were investigated and evaluated. The results show that, compared with the "perfect" model, the rigidity and toughness of defective models are decreased, while the ductility, tenacity and plastic properties are enhanced. The binding energies, interaction energy of the trigger bond, and the cohesive energy density of defective crystals declined, thus implying that stabilities are weakened, the explosive molecule is activated, trigger bond strength is diminished and safety is worsened. Detonation performance showed that, owing to the influence of crystal defects, the density is lessened, detonation pressure and detonation velocity are also declined, i.e., the power of defective explosive is decreased. In a word, the crystal defects may have a favorable effect on the mechanical properties, but have a disadvantageous influence on sensitivity, stability and energy density of CL-20/TNT cocrystal explosive. The results could provide theoretical guidance and practical instructions to estimate the properties of defective crystal models.

Theoretical investigation of the structures and properties of CL-20/DNB cocrystal and associated PBXs by molecular dynamics simulation.

In this work, a CL-20/DNB cocrystal explosive model was established and six different kinds of fluoropolymers, i.e., PVDF, PCTFE, F2311, F2312, F2313 and F2314 were added into the (1 0 0), (0 1 0), (0 0 1) crystal orientations to obtain the corresponding polymer bonded explosives (PBXs). The influence of fluoropolymers on PBX properties (energetic property, stability and mechanical properties) was investigated and evaluated using molecular dynamics (MD) methods. The results reveal a decrease in engineering moduli, an increase in Cauchy pressure (i.e., rigidity and stiffness is lessened), and an increase in plastic properties and ductility, thus indicating that the fluoropolymers have a beneficial influence on the mechanical properties of PBXs. Of all the PBXs models tested, the mechanical properties of CL-20/DNB/F2311 were the best. Binding energies show that CL-20/DNB/F2311 has the highest intermolecular interaction energy and best compatibility and stability. Therefore, F2311 is the most suitable fluoropolymer for PBXs. The mechanical properties and binding energies of the three crystal orientations vary in the order (0 1 0) > (0 0 1) > (1 0 0), i.e., the mechanical properties of the (0 1 0) crystal orientation are best, and this is the most stable crystal orientation. Detonation performance results show that the density and detonation parameters of PBXs are lower than those of the pure CL-20 and CL-20/DNB cocrystal explosive. The power and energetic performance of PBXs are thus weakened; however, these PBXs still have excellent detonation performance and are very promising. The results and conclusions provide some helpful guidance and novel instructions for the design and manufacture of PBXs.

Molecular dynamics calculation on structures, stabilities, mechanical properties, and energy density of CL-20/FOX-7 cocrystal explosives.

In this article, different CL-20/FOX-7 cocrystal models were established by the substitution method based on the molar ratios of CL-20:FOX-7. The structures and comprehensive properties, including mechanical properties, stabilities, and energy density, of different cocrystal models were obtained and compared with each other. The main aim was to estimate the influence of molar ratios on properties of cocrystal explosives. The molecular dynamics (MD) simulation results show that the cocrystal model with molar ratio 1:1 has the best mechanical properties and highest binding energy, so the CL-20/FOX-7 cocrystal model is more likely to form in 1:1 M ratio. The detonation parameters show that the cocrystal explosive exhibited preferable energy density and excellent detonation performance. In a word, the 1:1 cocrystal model has the best comprehensive properties, is very promising, and worth more theoretical investigations and experimental tests. This paper gives some original theories to better understand the cocrystal mechanism and provides some helpful guidance and useful instructions to help design CL-20 cocrystal explosives.

Comparative studies on structures, mechanical properties, sensitivity, stabilities and detonation performance of CL-20/TNT cocrystal and composite explosives by molecular dynamics simulation.

To investigate and compare the differences of structures and properties of CL-20/TNT cocrystal and composite explosives, the CL-20/TNT cocrystal and composite models were established. Molecular dynamics simulations were performed to investigate the structures, mechanical properties, sensitivity, stabilities and detonation performance of cocrystal and composite models with COMPASS force field in NPT ensemble. The lattice parameters, mechanical properties, binding energies, interaction energy of trigger bond, cohesive energy density and detonation parameters were determined and compared. The results show that, compared with pure CL-20, the rigidity and stiffness of cocrystal and composite models decreased, while plastic properties and ductility increased, so mechanical properties can be effectively improved by adding TNT into CL-20 and the cocrystal model has better mechanical properties. The interaction energy of the trigger bond and the cohesive energy density is in the order of CL-20/TNT cocrystal > CL-20/TNT composite > pure CL-20, i.e., cocrystal model is less sensitive than CL-20 and the composite model, and has the best safety parameters. Binding energies show that the cocrystal model has higher intermolecular interaction energy values than the composite model, thus illustrating the better stability of the cocrystal model. Detonation parameters vary as CL-20 > cocrystal > composite, namely, the energy density and power of cocrystal and composite model are weakened; however, the CL-20/TNT cocrystal explosive still has desirable energy density and detonation performance. This results presented in this paper help offer some helpful guidance to better understand the mechanism of CL-20/TNT cocrystal explosives and provide some theoretical assistance for cocrystal explosive design.

Theoretical insights into the effects of molar ratios on stabilities, mechanical properties, and detonation performance of CL-20/HMX cocrystal explosives by molecular dynamics simulation.

To research and estimate the effects of molar ratios on structures, stabilities, mechanical properties, and detonation properties of CL-20/HMX cocrystal explosive, the CL-20/HMX cocrystal explosive models with different molar ratios were established in Materials Studio (MS). The crystal parameters, structures, stabilities, mechanical properties, and some detonation parameters of different cocrystal explosives were obtained and compared. The molecular dynamics (MD) simulation results illustrate that the molar ratios of CL-20/HMX have a direct influence on the comprehensive performance of cocrystal explosive. The hardness and rigidity of the 1:1 cocrystal explosive was the poorest, while the plastic property and ductibility were the best, thus implying that the explosive has the best mechanical properties. Besides, it has the highest binding energy, so the stability and compatibility is the best. The cocrystal explosive has better detonation performance than HMX. In a word, the 1:1 cocrystal explosive is worth more attention and further research. This paper could offer some theoretical instructions and technological support, which could help in the design of the CL-20 cocrystal explosive.