Candidates Of High Energy Density Materials Research Articles

The coplanar family of bis(nitrotriazoles) tetrazine and oxides based as energetic compounds

AbstractSearching for energetic materials that balance detonation performance with sensitivity is an enduring ambition in the evolution of high‐energy density materials (HEDMs). The coplanar molecular structures of energetic compounds have a powerful impact on performance. Novel compounds of bis(nitrotriazoles) tetrazine (BNTT) were designed and investigated by density functional theory methods. The coplanar BNTT's oxides were a highlight in molecules with superior performance and acceptable sensitivities. Results showed that all these designed compounds possess high densities, positive heats of formation, remarkable detonation performance, and acceptable impact sensitivity. In particular, B1‐3 possessed higher density (ρ = 1.97 g cm−3) and exhibited good balance between detonation performance (Q = 1779.83 cal g−1, D = 9.48 km s−1, P = 42.01 GPa) and sensitivity (h50% = 28 cm) than trinitroperhydro‐1,3,5‐triazine (RDX). The theoretical study demonstrated that all designed compounds possess acceptable sensitivity. They were seen as the potential candidates of HEDMs.

Theoretical design of bis-azole derivatives for energetic compounds.

Bis-azole derivatives are a new class of energetic materials with features that include high nitrogen content, high heat of formation (HOF), high detonation performance and insensitivity to external stimuli. In this paper, 599 new bis-azole compounds were designed in a high-throughput fashion using bis-azole molecules of high density and high thermal decomposition temperature as the basic structure, and high energy groups such as nitro (–NO2) and amino groups (–NH2) as substituents. The molecular geometry optimization and vibration frequency analysis were performed using the DFT-B3LYP/6-311++G(d,p) method. The calculation results show that none of bis-azole derivatives exhibit a virtual frequency. Additionally, the density, heat of formation and characteristic height (h50) of the above compounds were obtained. Detonation performances were predicted by the Kamlet–Jacobs equations, and their structures and performances were studied. Furthermore, correlations between the performance parameters and the parent structure of the molecule, the number of substituting group and configuration were summarized, revealing promising potential candidates for high-energy density materials (HEDMs).

Theoretical investigation of a series of bis(1H-tetrazol-5-yl)furazan and bis(1H-tetrazol) derivatives as high-energy-density materials

ABSTRACTUsing density functional theory (DFT), a series of bis(1H-tetrazol-5-yl)furazan and bis(1H-tetrazol) derivatives with different linkages and substituents are investigated theoretically as potential high-energy-density materials (HEDMs). The heat of formation (HOF), detonation properties, natural bond orbital (NBO) and thermal stabilities are calculated and reported. The introduction of a furazan ring, an –N=N– bridge group and an –N3 substituent is beneficial to increase the HOF of the title compounds. NBO analysis shows that there are electronic delocalisation effects among the bridge groups, furazan and tetrazole rings, and substituted groups. The conjugation effects and electronic transitions are influenced by the different linkages and substituents. The estimated detonation velocities and pressures indicate that the –ONO2 and –NO2 groups and the –N=N– linkage play important roles in enhancing the detonation properties. The bond dissociation energy (BDE) calculations reveal that the –NO2 group is the substituent group which causes the least thermal stability. The bond between the substituent group and the tetrazole ring is the weakest bond in the title molecules. Considering the detonation performance and the thermal stability, 17 compounds may be promising candidates for HEDMs with good performance. Eight of them (A3, A4, C3, C4, D3, F3, G1 and G3) have better detonation properties than HMX.

Computational studies on energetic properties of nitrogen-rich energetic materials with ditetrazoles

Based on the full optimized molecular geometric structures at B3LYP/6-311++G**level, the densities (ρ), heats of formation (HOFs), detonation velocities (D) and pressures (P) for a series of ditetrazoles derivatives, were investigated to look for high energy density materials (HEDMs). The results show that the influence of different substituted groups on HOFs has the order of -N3>-CN>-NH2>-NO2>-NF2>-ONO2>-H>-CH3>-CF3. The introduction of -CF3 groups is more favourable for increasing the density and the introduction of -CH3 groups is not favourable for increasing the density. In addition, all the series combined with -NF2 group except B-NF2 all have higher densities, larger D and P. F-NF2 may be regarded as the potential candidates of HEDMs because of the largest detonation velocity and pressure among these derivatives. The energy gaps between the HOMO and LUMO of the studied compounds are also investigated. Computational results show that ditetrazoles combined with -NF2 group except B-NF2 have higher densities, larger D and P. F-NF2 may be regarded as the potential candidate of HEDMs because of the largest detonation velocity and pressure among these derivatives.

Theoretical studies on energetic materials bearing pentaflurosulphyl (SF 5 ) groups

Heats of formation (HOF) for a series of energetic materials containing SF5 group were studied by density functional theory. Results show that HOFs increase with the augmention of field effects of substituted groups. Addition of furazan or furoxan ring increases HOF of the energetic materials. All the SF5-containing compounds have densities which are ∼0.19 g/cm3 higher than those containing –NH2 group. S–F bond is the trigger bond for the thermolysis process in the title compounds and bond dissociation energies of the weakest bonds range from 351.1 to 388.3 kJ/mol. Detonation velocities (D) and pressures (P) are evaluated by Kamlet–Jacobs equations with the calculated densities and HOFs. Results show that increasing the amount of furazan rings results in a larger D and P. Considering the detonation performance and thermal stability, eight compounds may be considered as potential candidates for high-energy density materials. SF5 group is an important energetic group. Considering the importance of the SF5 group, a series of energetic materials containing SF5 group were investigated to discuss the HOF, BDE and detonation properties in order to search for compounds with better performance.

Dft theoretical study of energetic nitrogen-rich C4N6H8-n(NO2)n derivatives

Density functional theory (DFT) calculations at the B3LYP/6-31G** theoretical level were performed for a series of guanidine-fused bicyclic skeleton derivatives C4N6H8-n(NO2)n (n = 1 - 6). The heats of formation (HOFs) were calculated by isodesmic reactions, and the detonation properties were evaluated using the Kamlet - Jacobs equations. The bond dissociation energies were also analyzed to investigate the thermal stability and sensitivity of the compounds. The results show that all of the derivatives have high positive HOFs, compound G has the highest theoretical density, and compound F1 has the highest detonation velocity and detonation pressure. Considering both the detonation properties and thermal stabilities, compounds D1 and D4 (3 nitro substituents), E1 - E6 (4 nitro substituents), and G (6 nitro substituents) can be regarded as potential candidates for high-energy density materials.

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.

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.

Characterization of nitrogen-bridged 1,2,4,5-tetrazine-, furazan-, and 1H-tetrazole-based polyheterocyclic compounds: heats of formation, thermal stability, and detonation properties

The heats of formation (HOFs), thermal stability, and detonation properties for a series of nitrogen-bridged 1,2,4,5-tetrazine-, furazan-, and 1H-tetrazole-based polyheterocyclic compounds (3,6-bis(1H-1,2,3,4-tetrazole-5-ylamino)-1,2,4,5- tetrazine (TST), 3,6-bis(furazan-5-ylamino)-1,2,4,5-tetrazine (FSF), 3,4-bis(1,2,4,5- tetrazine-3-ylamino)-furazan (SFS), 3,4-bis(1H-1,2,3,4-tetrazole-5-ylamino)-furazan (TFT), 1,5-bis(1,2,4,5-tetrazine-3-ylamino)-1H-1,2,3,4-tetrazole (STS), and 1,5-bis(furazan-3-ylamino)-1H-1,2,3,4-tetrazole (FTF) derivatives) were systematically studied by using density functional theory. The results show that the -N(3) or -NHNH(2) group plays a very important role in increasing the HOF values of the derivatives. Among these series, the SFS derivatives have lower energy gaps, while the TFT derivatives have higher ones. Incorporation of the -NH(2) group into the FSF, SFS, STS, or FTF ring is favorable for enhancing its thermal stability, whereas the substitution of the -NHNH(2) group could increase the thermal stability of the TST, SFS, STS, or FTF ring. The calculated detonation properties indicate that the -NO(2) or -NF(2) is very helpful for enhancing the detonation performance for these derivatives. Considering the detonation performance and thermal stability, six derivatives may be regarded as promising candidates of high-energy density materials (HEDMs). These results provide basic information for the molecular design of novel HEDMs.

Comparative Theoretical Studies of Energetic Azo s-Triazines

In this work, the properties of the synthesized high-nitrogen compounds 4,4',6,6'-tetra(azido)azo-1,3,5-triazine (TAAT) and 4,4',6,6'-tetra(azido)hydrazo-1,3,5-triazine (TAHT), and a set of designed bridged triazines with similar bridges were studied theoretically to facilitate further developments for the molecules of interests. The gas-phase heats of formation were predicted based on the isodesmic reactions by using the DFT-B3LYP/AUG-cc-PVDZ method. The estimates of the condensed-phase heats of formation and heats of sublimation were estimated in the framework of the Politzer approach. Calculation results show that the method gives a good estimation for enthalpies, in comparison with available experimental data for TAAT and TAHT. The crystal density has been computed using molecular packing calculations. The calculated detonation velocities and detonation pressures indicate that -NF(2), -NO(2), -N═N-, and -N═N(O)- groups are effective structural units for improving the detonation performance of the bridged triazines. The synthesized TAAT and TAHT are not preferred energetic materials due to their inferior detonation performance. The p→π conjugation effect between the triazine rings and bridges makes the molecule stable as a whole. The electrostatic behavior of the bridged triazines is characterized by an anomalous surface potential imbalance when incorporating the strongly electron-withdrawing -NF(2) and -NO(2) groups into the molecule. An analysis of the bond dissociation energies shows that all these derivatives have good thermal stability over RDX and HMX, and the -NH-NH- bridge is more helpful for improving the stability than -N═N(O)- and -N═N- bridges. Considering the detonation performance and thermal stability, three bridged triazines may be considered as the potential candidates of high-energy density materials (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.

Theoretical studies on the structure and detonation properties of amino-, methyl-, and nitro-substituted 3,4,5-trinitro-1 H-pyrazoles

In this study, 3,4,5-trinitro-1 H-pyrazole ( R20), 3,4,5-trinitro-1 H-pyrazol-1-amine ( R21), 1-methyl-3,4,5-trinitro-1 H-pyrazole ( R22), and 1,3,4,5-tetranitro-1 H-pyrazole ( R23) have been considered as potential candidates for high-energy density materials by quantum chemical treatment. The geometric and electronic structures, band gap, thermodynamic properties, crystal density and detonation properties were studied using density functional theory at the B3LYP/aug-cc-pVDZ level. The calculated energy of explosion, density, and detonation performance of model compounds are comparable to 1,3,5-trinitro-1,3,5-triazinane (RDX), and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). Atoms-in-molecules (AIM) analyses have also been carried to understand the nature of intramolecular interactions and the strength of trigger bonds.

DFT study on energetic tetrazolo-[1,5- b]-1,2,4,5-tetrazine and 1,2,4-triazolo-[4,3- b]-1,2,4,5-tetrazine derivatives

The heats of formation (HOFs) for a series of tetrazolo-[1,5- b]-1,2,4,5-tetrazine (TETZ) and 1,2,4-triazolo-[4,3- b]-1,2,4,5-tetrazine (TTZ) derivatives were studied by using density functional theory. The results show that the substitution of the –N 3 or –N(NO 2) 2 group in the TETZ or TTZ ring extremely enhances its HOF values. For monosubstituted case, attachment of a substituent to position 8 in the TETZ or TTZ ring will increase its energy gaps except for the derivatives with the –NO 2 group. It is also found that the energy gap of TTZ can be tuned by incorporating a substituent into different positions in the parent ring. The substitution of the –NH 2 group in the TETZ ring is favorable for enhancing its thermal stability. For the TTZ ring, different substituted positions and number of the substituent might affect its thermal stability. The calculated detonation properties indicate that incorporating the –NO 2, –NF 2, –ONO 2, or –N(NO 2) 2 group into the TETZ or TTZ ring is very helpful for enhancing its detonation performance. Considered the detonation performance and thermal stability, four derivatives may be regarded as the promising candidates of high-energy density materials (HEDMs).

Molecular Design of 3,3′-Azobis-1,2,4,5-tetrazine-Based High-Energy Density Materials

We systematically studied the heats of formation (HOFs) for a series of 3,3' -azobis-1,2,4, 5-tetrazine derivatives by density functional theory (DFT). The results show that the —N3 group plays a very important role in increasing the HOFs for these derivatives. An analysis of the bond dissociation energies for the weakest bonds indicates that the attachment of —NH2 or —N3 group to 3,3' -azobis-1,2,4, 5-tetrazine is favorable in enhancing its thermal stability. The calculated detonation velocities (D) and pressures (p) indicates that —NO2 or —NF2 largely enhances the detonation performance of the derivatives. Considering the detonation performance and the thermal stability, the three derivatives may be regarded to be promising candidates for high-energy density materials (HEDMs).

Comparative Theoretical Studies of Energetic Substituted Carbon- and Nitrogen-Bridged Difurazans

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 difurazan derivatives with different linkages and substituent groups. The results show that the -N(3) group and azo bridge (-N=N-) play a very important role in increasing the HOF values of the difurazan derivatives. The effects of the substituents on the HOMO-LUMO gap are combined with those of the bridge groups. The calculated energetic properties indicate that the -ONO(2), -NO(2), -NF(2), -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-O bond in the ring is the weakest one and the ring cleavage is possible to happen in thermal decomposition. On the whole, the -NH-NH-, -N=N-, or -N(O)=N- group is an effective bridge for enhancing the thermal stability of the derivatives. Considered the detonation performance and thermal stability, five compounds may be considered as the potential candidates of high-energy density materials (HEDMs).

Molecular Design of 1,2,4,5-Tetrazine-Based High-Energy Density Materials

The heats of formation (HOFs) for a series of 1,2,4,5-tetrazine derivatives were calculated by using density functional theory (DFT), Hartree Fork (HF), and Møller-Plesset (MP2) as well as semiempirical methods. The effects of different basis bets on HOFs were also considered. Our results show that the -CN or -N3 group plays a very important role in increasing the HOF values of the 1,2,4,5-tetrazine derivatives. An analysis of the bond dissociation energies for the weakest bonds indicates that substitutions of the -N3, -NH2, -CN, -OH, or -Cl group are favorable for enhancing the thermal stability of 1,2,4,5-tetrazine, but the -NHNH2, -NHNO2, -NO2, -NF2, or -COOH group produces opposite effects. The calculated detonation velocities and pressures indicate that the -NF2 or -NO2 group is very helpful for enhancing the detonation performance for the derivatives, but the case is quite the contrary for the -CN, -NH2, or -OH group. Considered the detonation performance and thermal stability, three derivatives may be regarded as potential candidates of high-energy density materials (HEDMs).

Structures and Properties of Closed Ladderanes C24H24, Laddersilanes Si24H24, and Their Nitrogen-Containing Isoelectronic Equivalents: A G3(MP2) Investigation

An investigation has been undertaken to study the large closed ladderanes C(24)H(24) and their analogs. Thirteen isoelectronic species have been identified as local minima on the MP2(FU)/6-31G(d) potential energy surface, including three C(24)H(24), four Si(24)H(24), two N(24,) and four C(24-x)H(24-x)N(x) (x = 6, 8, 12) isomers. Of these 13 species, 11 are reported for the first time. Their structures, stabilities, HOMO-LUMO gaps, and G3(MP2) heats of formations are computationally obtained and discussed. These results are also compared with those of the related species already available in the literature. Our results show that molecules with 12-membered rings are highly energetic and much less stable than their corresponding isomers that do not have such rings. Isomer II of Si(24)H(24) with anticonformations has a very small HOMO-LUMO gap of 2.56 eV, approaching the semiconductor range. Therefore, it is a candidate of potential semiconductor materials. Meanwhile, the N(24) and other nitrogen-containing species are candidates for high-energy density materials. Our results also indicate that C(18)H(18)N(6) and C(16)H(16)N(8) may be good hexa- and octadentate ligands for metal cations.

A DFT study on nitrotriazines

In this study, all possible mono-, di- and tri-nitro-substituted triazine compounds have been considered as potential candidates for high-energy density materials (HEDMs) by using quantum chemical treatment. Geometric and electronic structures, thermodynamic properties and detonation performances of these nitro-substituted triazines have been systematically studied using density functional theory (DFT, B3LYP) at the level of 6-31G(d,p), 6-31+G(d,p), 6-311G(d,p), 6-311+G(d,p) and cc-pVDZ basis sets. Moreover, thermal stabilities have been evaluated from the homolytic bond dissociation energies (BDEs). Detailed molecular orbital (MO) investigation has been performed on these potential HEDMs. According to the results of the calculations, mono-, di- and tri-nitro-substituted derivatives of symmetric 1,3,5-triazine have been found to be more stable than their 1,2,3 and 1,2,4 counterparts.

Computational Studies on Polynitrohexaazaadmantanes as Potential High Energy Density Materials

Polynitrohexaazaadamantanes (PNHAAs) have been the subject of much recent research because of their potential as high energy density materials (HEDMs). The B3LYP/6-31G method was employed to evaluate the heats of formation (HOFs) for PNHAAs by designing isodesmic reactions. The HOFs are found to be correlative with the number (n) and the space orientations of nitro groups. Detonation velocities (D) and detonation pressures (P) were estimated for PNHAAs by using the well-known Kamlet-Jacobs equations, based on the theoretical densities (rho) and HOFs. It is found that D and P increase as n ranges from 1 to 6, and PNHAAs with 4-6 nitro groups meet the criteria of an HEDM. When n is over 6, rho of PNHAAs slightly increases; however, the chemical energy of detonation (Q) decreases so greatly that both D and P decrease. The calculations on bond dissociation energies suggest that the N-N bond be the trigger bond during the pyrolysis initiation process of each PNHAA, and with increasing n, N-N bond dissociation energy (E(N-N)) decreases on the whole, that is to say, the relative stability of PNHAAs decreases. All E(N-N)(s) of PNHAAs are more than 30 kcal.mol(-1), which further proves that four PNHAAs with 4-6 nitro groups can be used as the candidates of HEDMs. Considering the synthesis difficulty and the performance as an energetic compound, we finally recommended 2,4,6,8,10-pentanitrohexaazaadamantane as the target HEDM for PNHAAs.

Theoretical Studies on the Structures, Thermodynamic Properties, Detonation Properties, and Pyrolysis Mechanisms of Spiro Nitramines

Density function theory (DFT) has been employed to study the geometric and electronic structures of a series of spiro nitramines at the B3LYP/6-31G level. The calculated results agree reasonably with available experimental data. Thermodynamic properties derived from the infrared spectra on the basis of statistical thermodynamic principles are linearly correlated with the number of nitramine groups as well as the temperature. Detonation performances were evaluated by the Kamlet-Jacobs equations based on the calculated densities and heats of formation. It is found that some compounds with the predicted densities of ca. 1.9 g/cm3, detonation velocities over 9 km/s, and detonation pressures of about 39 GPa (some even over 40 GPa) may be novel potential candidates of high energy density materials (HEDMs). Thermal stability and the pyrolysis mechanism of the title compounds were investigated by calculating the bond dissociation energies (BDE) at the B3LYP/6-31G level and the activation energies (E(a)) with the selected PM3 semiempirical molecular orbital (MO) based on the unrestricted Hartree-Fock model. The relationships between BDE, E(a), and the electronic structures of the spiro nitramines were discussed in detail. Thermal stabilities and decomposition mechanisms of the title compounds derived from the B3LYP/6-31G BDE and the UHF-PM3 E(a) are basically consistent. Considering the thermal stability, TNSHe (tetranitrotetraazaspirohexane), TNSH (tetranitrotetraazaspiroheptane), and TNSO (tetranitrotetraazaspirooctane) are recommended as the preferred candidates of HEDMs. These results may provide basic information for the molecular design of HEDMs.