Computational investigation of the heat of formation, detonation properties of furazan-based energetic materials

The heats of formation (HOFs) for a series of furazan-based energetic materials were calculated by density functional theory. The isodesmic reaction method was employed to estimate the HOFs. The result shows that the introductions of azo and azoxy groups can increase the HOF, but the introduction of azo group can increase the more HOF, when compared with azoxy group. The detonation velocities and detonation pressures of the furazan-based energetic materials are further evaluated at B3LYP/6-31G* level. Dioxoazotetrafurazan and azoxytetrafurazan may be regarded as the potential candidates of high-energy density materials because of good detonation performance. In addition, there are good linear correlations between OB and detonation velocities, and OB and detonation pressures. The energy gaps between the HOMO and LUMO of the studied compounds are also investigated. These results provide basic information for the molecular design of novel high-energy density materials.     

Molecular design of trinitromethyl-substituted nitrogen-rich heterocycle derivatives with good oxygen balance as high-energy density compounds

Density functional theory method was used to study the heats of formation (HOFs), electronic structure, energetic properties, and pyrolysis mechanism of a series of trinitromethyl-substituted heterocycle (including triazole, tetrazole, furazan, tetrazine, and fused heterocycles) derivatives. It is found that the fused ring, tetrazine, and tetrazole are effective structural units for increasing the HOFs of the derivatives. The substitution of the combination of nitro and trinitromethyl is very useful for improving their HOFs. The calculated energetic properties indicate that the combination of the nitro and trinitromethyl is very helpful for improving their detonation properties and oxygen balances (OB). Most of the title compounds have a good OB over zero. The OB of six compounds are very high and over 22. An analysis of the bond dissociation energies for several relatively weak bonds suggests that the N–O bond in the ring is a trigger bond for BIII-1, CI-3, and CI-4, and the ring–NO₂ and (NO₂)₂C–NO₂ bond cleavage is likely to happen in thermal decomposition for the remaining compounds. Considering the detonation performance and thermal stability, seven compounds could be regarded as potential candidates for high-energy compounds. Four compounds may be used as the novel high-energy oxidizers.     

Computational study on energetic properties of nitro derivatives of furan substituted azoles

Density functional theory has been used to investigate geometries, heats of formation (HOFs), C-NO₂ bond dissociation energies (BDEs), and relative energetic properties of nitro derivatives of azole substituted furan. HOFs for a series of molecules were calculated by using density functional theory (DFT) and Møller–Plesset (MP2) methods. The density is predicted using crystal packing calculations; all the designed compounds show density above 1.71 g/cm³. The calculated detonation velocities and detonation pressures indicate that the nitro group is very helpful for enhancing the detonation performance for the designed compounds. Thermal stabilities have been evaluated from the bond dissociation energies. Charge on the nitro group was used to assess the impact sensitivity in this study. According to the results of the calculations, tri- and tetra-nitro substituted derivatives reveal high performance with better thermal stability.     

Theoretic design of 1,2,3,4-tetrazine-1,3-dioxide-based high-energy density compounds with oxygen balance close to zero

Density functional theory method was used to study the heats of formation (HOFs), electronic structure, energetic properties, and thermal stability for a series of 1,2,3,4-tetrazine-1,3-dioxide derivatives with different substituents and bridge groups. It is found that the groups –NO₂, –C(NO₂)₃, and –N=N– play a very important role in increasing the HOFs of the derivatives. The effects of the substituents on the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels and HOMO–LUMO gaps are coupled to those of different substituents and bridges. The calculated detonation velocities and pressures indicate that the group –NO₂, –NF₂, –ONO₂, –C(NO₂)₃, or –NH– is an effective structural unit for enhancing the detonation performance for the derivatives. An analysis of the bond dissociation energies for several relatively weak bonds indicates that incorporating the groups –NO₂, –NF₂, –ONO₂, –C(NO₂)₃, and –N=N– into parent ring decreases their thermal stability. Considering the detonation performance and thermal stability, 18 compounds may be considered as the target compounds holding the greatest potential for synthesis and use as high-energy density compounds. Among them, the oxygen balances of four compounds are equal to zero. These results provide basic information for the molecular design of the novel high-energy compounds.     

Theoretical studies on the heats of formation, detonation properties, and pyrolysis mechanisms of energetic cyclic nitramines

Density functional theory calculations were performed to find comprehensive relationships between the structures and performance of a series of highly energetic cyclic nitramines. The isodesmic reaction method was employed to estimate the heat of formation. The detonation properties were evaluated by using the Kamlet-Jacobs equations based on the theoretical densities and HOFs. Results indicate the N-NO(2) group and aza N atom are effective substituents for enhancing the detonation performance. All cyclic nitramines except C11 and C21 exhibit better detonation performance than HMX. The decomposition mechanism and thermal stability of these cyclic nitramines were analyzed via the bond dissociation energies. For most of these nitramines, the homolysis of N-NO(2) is the initial step in the thermolysis, and the species with the bridged N-N bond are more sensitive than others. Considering the detonation performance and thermal stability, twelve derivatives may be the promising candidates of high energy density materials (HEDMs). The results of this study may provide basic information for the further study of this kind of compounds and molecular design of novel HEDMs.     

Computational study of energetic nitrogen‐rich derivatives of 1,1′‐ and 5,5′‐bridged ditetrazoles

Density functional theory method was used to study the heats of formation (HOFs), electronic structure, energetic properties, and thermal stability for a series of bridged ditetrazole derivatives with different linkages and substituent groups. The results show that the ? N₃ group and azo bridge (? N?N? ) play a very important role in increasing the HOF values of the ditetrazole derivatives. The effects of the substituents on the HOMO–LUMO gap are combined with those of the bridge groups. The calculated detonation velocities and detonation pressures indicate that the ? NO₂, ? NF₂, ? N?N? , or ? N(O)?N? group is an effective structural unit for enhancing the detonation performance for the derivatives. An analysis of the bond dissociation energies for several relatively weak bonds suggests that the N? N bond in the ring or outside the ring is the weakest one and the N? N cleavage is possible to happen in thermal decomposition. Overall, the ? CH₂? CH₂? or ? NH? NH? group is an effective bridge for enhancing the thermal stability of the bridged ditetrazoles. Because of their desirable detonation performance and thermal stability, five compounds may be considered as the potential candidates of high‐energy density materials (HEDMs). These results provide basic information for the molecular design of novel HEDMs. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011     

Prediction of the properties and thermodynamics of formation for energetic nitrogen‐rich salts composed of triaminoguanidinium cation and 5‐nitroiminotetrazolate‐based anions

Density functional theory and volume‐based thermodynamics calculations were performed to study the effects of different substituents and linkages on the densities, heats of formation (HOFs), energetic properties, and thermodynamics of formation for a series of energetic nitrogen‐rich salts composed of triaminoguanidinium cation and 5‐nitroiminotetrazolate anions. The results show that the ? NO₂, ? NF₂, or ? N₃ group is an effective substituent for increasing the densities of the 5‐nitroiminotetrazolate salts, whereas the effects of the bridge groups on the density are coupled with those of the substituents. The substitution of the group ? NH₂, ? NO₂, ? NF₂, ? N₃, or the nitrogen bridge is helpful for increasing the HOFs of the salts. The calculated energetic properties indicate that the ? NO₂, ? NF₂, ? N₃, or ? N?N? group is an effective structural unit for improving the detonation performance for salts. The thermodynamics of formation of the salts show that all the salts may be synthesized easily by the proposed reactions. The structure‐property relationships provide basic information for the molecular design of novel high‐energy salts. © 2012 Wiley Periodicals, Inc.     

Density function theory study on energetic nitro-triaziridine derivatives

The series of nitro-triaziridines had been studied as high-energy density compounds at B3LYP/6-311G** and MP2/6-311G** levels by means of density functional theory. The heats of formation (HOFs), bond dissociation energies, and detonation performance had been calculated in detail. It was found that all nitro-triaziridines have high position HOFs, and electron-withdrawing of nitro, the steric hindrance, and abundant N–N bond had positive effect with increasing values of HOFs. The thermodynamic stability is estimated by bond dissociation energy and available free space per molecule in unit cell. The detonation performance had been estimated via Kamlet–Jacobs equation and relative specific, However, two different consequences were obtained for detonation performance. Hence, for nitro-triaziridines derivatives, we assumed that a large number of extra oxygen was produced in combustion reaction or explosive reaction, which was negative for the energy released. Therefore, the oxygen balance must be considered for designing high-energy compounds. We also assumed that the Kamlet–Jacobs equation may not be applicable for the compounds, which was constituted of only oxygen, hydrogen, and nitrogen elements.     

Searching for a new family of modified CL-20 cage derivatives with high energy and low sensitivity

A new family of energetic caged compounds was designed by introducing -NH- into the CL-20 skeleton and their energetic properties and impact sensitivity were investigated by using density functional theory. The results indicate that favorable substitution positions of the amine groups in the skeleton is helpful for increasing the heats of formation. Most of the seven compounds have high crystal densities above 1.9 g/cm³. Five compounds have the predominant detonation properties over CL-20. The derivatives with one NH₂ group have lower impact sensitivity than those with two NH₂ groups. Taking the detonation performance and impact sensitivity into consideration, four compounds may be selected as the potential candidates of high energy density compounds.     

Theoretical studies on four-membered ring compounds with NF2, ONO2, N3, and NO2 groups

Density functional theory (DFT) method has been employed to study the geometric and electronic structures of a series of four-membered ring compounds at the B3LYP/6-311G** and the B3P86/6-311G** levels. In the isodesmic reactions designed for the computation of heats of formation (HOFs), 3,3-dimethyl-oxetane, azetidine, and cyclobutane were chosen as reference compounds. The HOFs for N(3) substituted derivations are larger than those of oxetane compounds with --ONO2 and/or --NF2 substituent groups. The HOFs for oxetane with --ONO2 and/or --NF2 substituent groups are negative, while the HOFs for N3 substituted derivations are positive. For azetidine compounds, the substituent groups within the azetidine ring affect the HOFs, which increase as the difluoroamino group being replaced by the nitro group. The magnitudes of intramolecular group interactions were predicted through the disproportionation energies. The strain energy (SE) for the title compounds has been calculated using homodesmotic reactions. For azetidine compounds, the NF2 group connecting N atom in the ring decrease the SE of title compounds. Thermal stability were evaluated via bond dissociation energies (BDE) at the UB3LYP/6-311G** level. For the oxetane compounds, the O--NO2 bond is easier to break than that of the ring C--C bond. For the azetidine and cyclobutane compounds, the homolyses of C--NX2 and/or N--NX2 (X = O, F) bonds are primary step for bond dissociation. Detonation properties of the title compounds were evaluated by using the Kamlet-Jacobs equation based on the calculated densities and HOFs. It is found that 1,1-dinitro-3,3-bis(difluoroamino)-cyclobutane, with predicted density of ca. 1.9 g/cm(3), detonation velocity (D) over 9 km/s, and detonation pressure (P) of 41 GPa that are lager than those of TNAZ, is expected to be a novel candidate of high energy density materials (HEDMs). The detonation data of nitro-BDFAA and TNCB are also close to the requirements for HEDMs.     

Substituent effects on heats of formation, group interactions, and detonation properties of polyazidocubanes

We have calculated the heats of formation (HOFs) for a series of polyazidocubanes by using the density functional theory (DFT), Hartree-Fock, and MP2 methods with 6-31G* basis set as well as semiempirical methods. The cubane skeleton was chosen for a reference compound, that is, the cubane skeleton was not broken in the process of designing isodesmic reactions. There exists group additivity for the HOF with respect to the azido group. The semiempirical AM1 method also produced reliable results for the HOFs of the title compounds, but the semiempirical MINDO3 did not. The relationship between HOFs and molecular structures was discussed. It was found that the HOF increases 330-360 kJ/mol for each additional number of the azido group being added to the cubane skeleton. The distance between azido groups slightly influences the values of HOFs. The interacting energies of neighbor azido groups in polyazidocubanes are in the range of 2.3 approximately 6.6 kJ/mol, which are so small and less related to the substituent numbers. The average interaction energy between nearest neighbor --N3 groups in the most stable conformer of octaazidocubane is 2.29 kJ/mol at the B3LYP/6-31G* level. The relative stability related to the number of azido groups of the title compounds was assessed based on the calculated HOFs, the energy gaps between the frontier orbitals, and the bond orders of the C--N3 and C--C bonds. The predicted detonation velocity of hepta- and octa-derivatives is over 9 km/s, and the detonation pressure of them is ca. 40 GPa or over.     

高能量密度材料3,3′-偶氮-1,2,4,5-四嗪衍生物的分子设计

运用密度泛函理论(DFT)方法,计算系列3,3′-偶氮-1,2,4,5-四嗪衍生物的生成热.结果显示:—N3取代基在增加3,3′-偶氮-1,2,4,5-四嗪衍生物的生成热方面起了非常重要的作用.通过分析标题化合物的最弱键离解能发现:—NH2或—N3取代基非常有利于增加衍生物的热稳定性.计算的爆速(D)和爆压(p)数值表明:—NO2或—NF2取代基有利于提高3,3′-偶氮-1,2,4,5-四嗪衍生物的爆轰性能.综合爆轰性能和热稳定性的计算结果,3种3,3′-偶氮-1,2,4,5-四嗪衍生物可以作为潜在的品优高能量密度材料(HEDM)候选物.     

Theoretical predictions on pentaerythritol tetranitrate-based high energy density compounds

A novel family of pentaerythritol tetranitrate (PETN) derivatives based parent PETN skeleton were designed by introducing two energetic groups –NF₂ and –NO₂. Their electronic structure, heats of formation, detonation properties, impact sensitivity, and thermal stability were investigated by using density functional theory. The findings reveal that most of the title compounds have good detonation performance. The –NF₂ group played an important role in improving the densities, heats of detonation, and detonation properties of the designed molecules. The values of h₅₀ for almost all the PETN derivatives are higher than that of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine. An analysis of bond dissociation energy suggests that the N-NO₂ bond tends to be a trigger bond in thermal decomposition. Taking both detonation properties and thermal stabilities into consideration, the three compounds may be selected as potential high-energy-density compounds.     

Theoretical studies of furoxan-based energetic nitrogen-rich compounds

Density functional theory calculations were performed to study the effects of different substituents and nitrogen-containing heterocyclic rings on the heats of formation (HOFs), energetic properties, and thermal stability for a series of furoxan derivatives. The isodesmic reaction method was employed to calculate the HOFs of the derivatives using total energies obtained from electronic structure calculations. The detonation velocities and pressures were evaluated by using the semiempirical Kamlet–Jacobs equations, based on the theoretical densities and HOFs. The bond dissociation energies and bond orders for the weakest bonds were analyzed to investigate the thermal stability of the furoxan derivatives. These results provide basic information for the molecular design of novel high energy density materials.     

Theoretical studies on heats of formation,detonation properties,and bond dissociation energies of monofurazan derivatives

The heats of formation (HOFs) for a series of monofurazan derivatives were calculated by using density functional theory. It is found that the ? CN or ? N₃ group plays a very important role in increasing the HOF values of the furazan derivatives. The detonation velocities and detonation pressures of the furazan derivatives are evaluated at two different levels. The results show that the ? NF₂ group is very helpful for enhancing the detonation performance for the furazan derivatives, but the case is quite the contrary for the ? CH₃ group. An analysis of the bond dissociation energies and bond orders for the weakest bonds indicate that the substitutions of ? CN group are favorable and enhances the thermal stability of the furazan derivatives, but the ? NO₂ groups produce opposite effects. These results provide basic information for the molecular design of novel high‐energy density materials. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Triazole‐Substituted Nitroarene Derivatives: Synthesis,Characterization, and Energetic Studies

A series of dense and energetic polynitroaryl‐1,2,4‐triazoles were synthesized through the nitration of aryl‐1,2,4‐triazoles. The Cu‐catalyzed/base‐mediated coupling reactions of haloarenes with 1,2,4‐triazoles delivered N‐aryl‐1,2,4‐triazoles. These new nitro‐rich‐aryltriazoles were characterized by analytical and spectroscopic methods. The solid‐state structures of most of these compounds were established by X‐ray diffraction analysis. Their thermal properties were determined by differential scanning calorimetry–thermogravimetric analysis. Their heats of formation (HOFs) and crystal densities were also calculated. The densities of the synthesized compounds ranged from 1.40 to 1.85 g cm^?3. Some of these newly synthesized compounds exhibited high positive HOFs, good thermal stabilities, high densities, and reasonable detonation velocities and pressures.     

Computational studies on tetrazole derivatives as potential high energy materials

The tetrazole is an important functionality of the most of energetic materials due to 80% nitrogen content, stability, and high enthalpy of formation. The present structure–property relationship study focuses on the optimized geometries of tetrazole derivatives obtained from density functional theory (DFT) calculations at B3LYP/6-31G* levels. The heat of formation (HOF) of tetrazole derivatives have been calculated by designing the appropriate isodesmic reactions. The increase in nitro groups on azole rings shows the remarkable increase in HOF. Density has been predicted by using CVFF force field. Increase in the nitro group increases the density. Detonation properties of the designed compounds were evaluated by using the Kamlet–Jacobs equation based on predicted densities and HOFs. Designed tetrazole derivatives show detonation velocity (D) over 8 km/s and detonation pressure (P) of about 32 GPa. Thermal stability was evaluated via bond dissociation energies (BDE) of the weakest C–NO₂ bond at B3LYP/6-31G* level. Charge on the nitro group has been used to assess the sensitivity correlation. Overall, the study implies that designed compounds of this series are found to be stable and expected to be the novel candidates of high energy materials (HEMs).     

Theoretical studies on the structures, heats of formation, energetic properties and pyrolysis mechanisms of nitrogen-rich difurazano[3,4-b:3′,4′-e]piperazine derivatives and their analogues

The molecular structure, heats of formation, energetic properties, strain energy and thermal stability for a series of substituted difurazano[3,4-b:3′,4′-e]piperazines and their analogues were studied using density functional theory. The results show that it is a useful way to increase the heat of formation values of energetic compounds by incorporating a five- or six-membered aromatic heterocycle to construct a fused ring system. The calculated detonation properties reveal that introducing one heterocycle to construct a fused ring structure greatly enhances their detonation properties. The substitution of the –NF₂, –NO₂ or –NHNO₂ group is very useful for enhancing the detonation performance for the substituted derivatives. According to molecular structure and natural bond orbital analysis, the introduction of the –NO₂, –NF₂ or –NHNO₂ group decreases the stability of the substituted derivative. There is a weak N–NO₂ bond conjugation in the NO₂-substituted derivatives. An analysis of the bond dissociation energies for several relatively weak bonds suggests that all the unsubstituted derivatives have good thermal stability, but the substitution of –NO₂ or –NF₂ remarkably decreases their stability. Considering the detonation performance and thermal stability, eight compounds may be considered as the potential candidates of high-energy density materials with less sensitivity.     

Density functional calculation on a high energy density compound having the formula C2OH4?n (NO2) n

A series of ethylene oxide derivations, C₂OH_4?Cn (NO2) _n (x?=?1?C4), has been designed computationally. We calculated the heats of formation (HOFs), bond dissociation energy (BDE), and explosive performances (detonation velocity and detonation pressure) of the title compounds by using density functional theory with 6-311G** basis set. The results show that most of ethylene oxide derivations have positive HOFs values except I. All the calculated BDE and the bond dissociation energies without zero-point energy corrections (BDE⁰) are larger than 200?kJ?mol^?1, which indicate that all the ethylene oxide derivations have good thermal stabilities. The explosive performances of most of ethylene oxide derivations would rank up with cyclotrimethylenetrinitramine (RDX). The results have not only shown that these compounds may be used as high energy density compounds, but also provide some useful information for further syntheses.     

DFT investigation on detonation properties and sensitivities of bridged triazolo[4,5-d]pyridazine based energetic materials

A series of bridged triazolo[4,5-d]pyridazine based energetic materials were optimized at B3LYP/6-311G(d, p) level of density functional theory (DFT), and their detonation properties and sensitivities were calculated. The results show that the  NN bridge/ N₃ group were beneficial to improve values of heats of formation while  NN bridge/ C(NO₂)₃ group can improve detonation properties remarkably. In view of the sensitivities, compound F2 possesses the minimum values of impact sensitivity which reveals that  NHNH bridge/ C(NO₂)₃ group will decrease the stability of the designed compounds. Take both of detonation properties and sensitivities into consideration, compounds C8, E7, E8, F8 were screened as candidates of potential energetic materials since these compounds possess similar detonation properties and sensitivities values to those of RDX. All the calculated results were except to shine lights on the design and synthesis of novel high energy density materials.