Nitro Group Charge Research Articles

Theoretical study on the correlation between the structure, excess energy, surface energy, electronic structure, nitro charge, and friction sensitivity of N,N'-dinitroethylenediamine (EDNA).

The sensitivity of energetic materials along different crystal directions is not the same and is anisotropic. In order to explore the difference in friction sensitivity of different surfaces, we calculated the structure, excess energy, surface energy, electronic structure, and the nitro group along (1 1 1), (1 1 0), (1 0 1), (0 1 1), (0 0 1), (0 1 0), and (1 0 0) surfaces of EDNA based on density functional theory. The analysis results showed that relative to other surfaces, the (0 0 1) surface has the shortest N-N average bond length, largest N-N average bond population, smallest excess energy and surface energy, widest band gap, and the largest nitro group charge value, which indicates that the (0 0 1) surface has the lowest friction sensitivity compared to other surfaces. Furthermore, the conclusions obtained by analyzing the excess energy are consistent with the results of the N-N bond length and bond population, band gap, and nitro charge. Therefore, we conclude that the friction sensitivity of different surfaces of EDNA can be evaluated using excess energy.

Theoretical study on BTF-based cocrystals: effect of external electric field.

The external electric field plays an important role in the sensitivity of cocrystal energetic materials. To reveal the influence of external electric field on benzotrifuroxan/2,4,6-trinitroaniline (BTF/TNA), benzotrifuroxan/trinitroazetidine (BTF/TNAZ), benzotrifuroxan/1,3,5-trinitrobenzene (BTF/TNB), and benzotrifuroxan/trinitrotoluene (BTF/TNT) cocrystals' sensitivity, atoms in molecules (AIM), frontier molecular orbitals, nitro group charges (QNO2), electron density values (ρ), electrostatic surface potentials (ESPs), bond dissociation energy (EBDE), and interaction energy (Eint) of the C-NO2 bond were calculated by density functional theory at M062X-D3/ma-def2 TZVPP and B3LYP-D3/6-311 + G (d, p) levels in this article. The results indicate that both negative and positive electric fields reduce the energy gap of the BTF-based cocrystals, and BTF/TNAZ is the most sensitive cocrystal among the four cocrystals. For BTF/TNA and BTF/TNB, the EBDE and the negative charge of the nitro group decreases with increasing positive electric field strength, the Vs max increases with positive electric field strength, and the sensitivity of cocrystal eventually tends to increase under the positive electric field. For BTF/TNAZ and BTF/TNT, the EBDE and the negative charge of the nitro group decrease with increasing negative electric field strength, the Vs max increases with negative electric field strength, and the sensitivity of cocrystal eventually tends to increase under the negative electric field. Finally, the variation in bond length, nitro charge, and AIM electron density values are well correlated with the strengths of the external electric field.

Density functional theory study of CL-20/Nitroimidazoles energetic cocrystals in an external electric field

The external electric field (EEF) has a significant influence on the sensitivity of the energetic cocrystal materials. In order to find out the relationship between the EEF and sensitivity of energetic cocrystals 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1,4-dinitroimidazole (CL-20/1,4-DNI), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-2,4-dinitro-1H-imidazole (CL-20/2,4-MDNI) and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-4,5-dinitro-1H-imidazole (CL-20/4,5-MDNI). In this work, density functional theory (DFT) at B3LYP-D3/6–311 + G(d,p) and M062X-D3/ma-def2 TZVPP levels were employed to calculate the bond dissociation energies (EBDE) of selected N-NO2 trigger bonds, frontier molecular orbitals, electrostatic potentials (ESPs) and nitro group charges (QNO2) under different EEF. The results show that as the positive electric field increases, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy gap and EBDE become smaller, and the local positive ESPs becomes larger so that the energetic cocrystals tends to have higher sensitivity. In addition, the linear fitting results show that the trigger bond length and nitro group charge changes are closely related to the EEF.

Theoretical prediction of the trigger linkage, cage strain, and explosive sensitivity of CL-20 in the external electric fields

In order to add safely external electric fields into the systems of the explosives with strong cage strain, the effects of the external electric fields on the strengths of trigger linkages, cage strain energies (CSEs), surface electrostatic potentials (ESPs), as well as impact and shock initiation sensitivities of CL-20 were investigated using the B3LYP and M06-2X methods with 6-311++G(2d,p) basis set. The results show that the changes of the strengths of the N-NO2 bonds are more notable than those of the bonds forming cage, and the changes involving the N-NO2 bonds attached to the five-membered ring are more significant than those attached to the six-membered ring. In most cases, the CSEs in the electric fields are stronger than those in no field. From the BDEs, the N-NO2 cleavage is the decomposition reaction pathway in detonation initiation. However, from the surface ESPs, the N-NO2 cleavage, C-N and C-C bond breaking may initiate the reactions. The global ESPs are more reasonable and reliable to estimate the impact sensitivities of the cage-shaped explosives. The changes of the bond lengths, Mulliken bond orders, nitro group charges and BDEs correlate well with the external electric field strengths. Interestingly, an abnormal result is found that the h50 values in the electric fields are larger than those in no field.

Correlation Between Molecular Charge Properties and Impact Sensitivity of Explosives: Nitrobenzene Derivatives

AbstractNitrobenzenic explosives can have high energy density and low impact sensitivity. In this work, the density functional theory (DFT) charge density of 50 nitrobenzenic molecules was analyzed using the Distributed Multipole Analysis (DMA) method to investigate the impact sensitivity of their explosives. The DMA monopole, dipole and quadrupole electric multipoles localized on the atoms of a molecule provide a very detailed picture of the molecular charge density and have a clear chemical interpretation. The DMA multipoles of each molecule were used to develop models correlating molecular charge properties and impact sensitivity of nitrobenzenic explosives, which is quantified by the quantity h50. Three models previously applied to 17 nitroaromatic molecules (J. Phys. Chem. A 115, 9055, 2011) are now examined for a larger dataset of 50 molecules. Model 1 used the nitro group charge as a single parameter for h50 prediction, Model 2 additionally included the quadrupole values of the benzene ring atoms (a measure of charge delocalization) and Model 3 included the dipole moment (indicator of site polarization) of the nitro groups of each molecule, as well as the average C−NO2 bond distance, which quantifies bond strength. Two additional new models that include the quadrupole values of the nitro group were also proposed. The original three models (Models 1–3), as well as the new models (4‐5), applied to the set of 50 nitrobenzenic molecules, displayed good results even when compared with the previous work. Among the computed DMA electrical multipole values, two proved to be essential for developing a good model, as found before for the smaller set: the DMA quadrupole values of the ring atoms that quantify the degree of electronic delocalization in the ring and the total DMA charge (monopole) values of the explosophore nitro group.

Theoretical prediction of the impact sensitivities of energetic C-nitro compounds.

In order to design high-energetic and insensitive explosives, the frontier orbital energy gaps, surface electrostatic potentials, nitro group charges, bond dissociation energies (BDEs) of the C-NO2 trigger bonds, and intermolecular interactions obtained by the M06-2X/6-311++G(2d,p) method were quantitatively correlated with the experimental drop hammer potential energies of 10 typical C-nitro explosives. The changes of several information-theoretic quantities (ITQs) in the density functional reactivity theory were discussed upon the formation of complexes. The BDEs in the explosives with six-membered ring are larger than those with five-membered ring. The frontier orbital energy gaps of the compounds with benzene ring are larger than those with N-heterocycle. The models involving the intermolecular interaction energies and the energy gaps could be used to predict the impact sensitivity of the C-nitro explosives, while those involving ΔSS, ΔIF, and ΔSGBP are invalid. With the more and more ITQs, the further studies are needed to seek for a good correlation between impact sensitivity measurements and ITQs for the energetic C-nitro compounds. The origin of sensitivity was revealed by the reduced density gradient method.

Derivatives of 3,6-Bis(3-aminofurazan-4-ylamino)-1,2,4,5-tetrazine: Excellent Energetic Properties with Lower Sensitivities.

To find a balance between energy and safety, a series of compounds based on azo-, azoxy-, 1,4,2,5-dioxadiazene-, and 3,6-diamino-1,2,4,5-tetrazine-bridged bis(aminofurazan) were designed and synthesized. These compounds were analyzed by nitro group charges (Qnitro) and bond dissociation energy (BDE) calculations, which are related to sensitivity and stability. Based on the calculated results, derivatives of 3,6-bis(3-aminofurazan-4-ylamino)-1,2,4,5-tetrazine have the largest values for -Qnitro and BDE of all of the bis(aminofurazan) compounds. This shows that compounds based on 3,6-bis(3-aminofurazan-4-ylamino)-1,2,4,5-tetrazine have the lowest sensitivities and best stabilities, which has been substantiated by experiments. Additionally, their explosive properties remain essentially competitive with compounds based on azo-, azoxy-, and 1,4,2,5-dioxadiazene-bridged bis(aminofurazan). Hirshfeld surface calculations were also performed to better understand the relationship between the molecular structure and stability/sensitivity. This work highlights the value of 3,6-diamino-1,2,4,5-tetrazine as a linker to achieve good balance between safety and energy.

Investigating geometric structure, energies, electronic structure and impact sensitivity illustrated with surfaces of ε-CL-20

The sensitivity of energetic compounds is different from one crystal direction to another, known to be anisotropic. To explore the effects of different surfaces on impact sensitivity, we investigate the structural properties, energies, electronic structure and impact sensitivity of various surfaces of ε-Cl-20 based on the first-principles calculations, the surfaces including (0 0 1), (0 1 0), (0 1 1), (0 1 2), (0 2 1), (1 0 0), (1 0 1), (1 0 2), (1 1 0), (1 1 1), (1 2 0), (2 0 1) and (2 1 0). It turns out that there is a good correlation between the N–N average bond population (Y) versus average bond lengths (X). The (1 0 2) surface has the most extended N–N average bond length, the lowest average bond population, the most substantial excess energy, and lowest nitro group charge, which indicate that (1 0 2) surface has the maximum impact sensitivity compared to other surfaces. There is a clear trend for band gap to decrease as excess energy becomes larger except (1 0 2) and (2 0 1) surfaces. The lower nitro group charge −QNO2 is, the more massive excess energy is, and the higher impact sensitivity is. The results indicate that the excess energy is regarded as a theoretical criterion of sensitivity to surfaces of ε-Cl-20.

Theoretical Study on CL-20-Based Cocrystal Energetic Compounds in an External Electric Field.

An external electric field has great effects on the sensitivity of cocrystal energetic materials. In order to find out the relationship between the external electric field and sensitivity of cocrystals 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/benzotrifuroxan (CL-20/BTF), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/3,4-dinitropyrazole (CL-20/DNP), and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-3,5-dinitro-1,2,4-triazole (CL-20/MDNT), density functional theory at B3LYP-D3/6-311+G(d,p) and M062X-D3/ma-def2 TZVPP levels was employed to calculate frontier molecular orbitals, atoms in molecules (AIM) electron density values, bond dissociation energies (BDEs) of the N–NO2 bond, impact sensitivity (H50), electrostatic potentials (ESPs), and nitro group charges (QNO2) in this work. The results show that a smaller highest occupied molecular orbital–lowest unoccupied molecular orbital gap and the BDEs, as well as H50, tend to have a larger sensitivity along with the positive directions in the external electric field. Moreover, a smaller local positive ESP (Vs max) leads to better stability in the negative electric field. The sensitivity of cocrystal molecules decreases gradually in the negative external electric field with the increase of negative nitro group charges. Finally, the change in the bond lengths, AIM electron density values, and nitro group charges correlate well with the external electric field strengths.

Design and exploration of 5-nitro-3-trinitromethyl-1H-1,2,4-triazole and its derivatives as energetic materials.

According to the fact that 5-nitro-3-trinitromethyl-1H-1,2,4 triazole (NTNMT) is a successful, good explosive, energetic groups such as -CH3, -NH2, -NHNO2, -NO2, -ONO2, -NF2, -CN, -NC, -N3 groups were introduced into NTNMT and their oxygen balance was at about zero. The energetic properties, detonation performance, and sensitivity were studied at the B3LYP/6-31G** level of density functional theory to seek for possible high energy density compounds. The effects of substituent groups on heat of formation (HOF), density ρ, detonation velocity D, detonation pressure P, detonation energy Q, and sensitivity (evaluated using oxygen balance OB, the nitro group charges -QNO2, and bond dissociation energies BDE were studied and discussed. The order of contribution of the substituent groups to ρ, D, and P was -NF2 > -ONO2 > -NO2 > -NHNO2 > -N3 > -NH2 > -NC > -CN > -CH3; while to HOF is -N3 > -NC > -CN > -NO2 > -NF2 > -ONO2 > -NH2 > -NHNO2 > -CH3. The trigger bonds in the pyrolysis process for NTNMT derivatives may be N-NO2, N-NH2, N-NHNO2, C-NO2, or O-NO2 varying with the attachment of different substituents. Results show that NTNMT-NHNO2, -NH2, -CN, and -NC derivatives have high detonation performance and good stability. In a word, the oxygen balance at about zero strategy in this work offers new routes for the improvement in properties and stabilities of energetic materials. In the present paper, several 5-nitro-3-trinitromethyl-1H-1,2,4 triazole (NTNMT) derivatives were designed. Their energetic properties, detonation performance, and sensitivity were studied at the B3LYP/6-31G** level of density functional theory (DFT) to seek for possible high energy density compounds (HEDCs). The different substituents have some changes in the influence on heat of formation (HOF), density ρ, detonation velocity D, detonation pressure P, detonation energy Q, and sensitivity. In a word, the oxygen balance at about zero strategy in this work offers new routes for the improvement in properties and stabilities of energetic materials.

Theoretical study on the structure and sensitivity of fused aza-cyclic nitro-containing compounds

As the heterocyclic compound with high detonation properties and low sensitivity, fused aza-cyclic energetic compounds have shown great research value and application prospect in recent years. In this paper, two series (30 kinds) of new fused aza-cyclic nitro-containing compounds were designed to be the research target, with good fused aza-cyclic molecules as the basic structure and nitrogen-containing high energy groups of nitro group (-NO2) and amino group (-NH2) as substituents. The DFT-B3LYP/6-31G (d) method was used to optimize the molecular geometry and analyze the vibration frequency. The calculation results show that all derivatives have no virtual frequency, and they are stable structures on the potential energy surface; The nitro group charge of compounds was obtained. The structure-activity relationship between molecular structure and sensitivity was studied. And change relation of the sensitivity and the parent structure of molecule, the type and number of substituting group and configuration was summarized, providing references for relevant researchers.

Theoretical prediction of the trigger linkages, surface electrostatic potentials, and explosive sensitivities of 1,4-dinitroimidazole-N-oxide in the external electric fields

In order to introduce effectively the external electric fields into the explosive systems, the change trends of the strengths of trigger linkages, nitro group charges, and explosive sensitivities of 1,4-dinitroimidazole-N-oxide (1,4-DNIO) were investigated in the external electric fields at the B3LYP/6-311++G(2d,p) and M06-2X/aug-cc-pVTZ levels. The formulas for calculating the impact sensitivity by the surface electrostatic potentials were discussed. The results show that the N-NO2 bond is always the most likely trigger linkage, followed by N → O. This is the very valuable information for the researchers engaged in the molecular design or synthesis of the energetic explosives: The influences of the weak N → O coordination bond attached to the aromatic ring on the explosive sensitivity can be ignored when the N-NO2 bond exists. In the external electric fields along the positive directions of the N → O and C-NO2 bond axes as well as the negative direction of the N-NO2 bond axis, the dissociation energies (BDEs) of the N-NO2 bond and h50 values are increased, leading to the decreased impact sensitivities. The changes of the bond lengths, AIM electron density values, nitro group charges, BDEs of the trigger linkages, and impact sensitivities correlate well with the external electric field strengths, respectively. The effects of the fields on the electric spark sensitivities and shock initiation pressures are not obvious. The essence of the low BDEs of the N-NO2 bond was revealed by the resonance theory of the aromatic ring. Graphical abstract Changes of the impact sensitivities versus field strengths.

Multimolecular Complexes of CL-20 with Nitropyrazole Derivatives: Geometric, Electronic Structure, and Stability.

The multimolecular complexes formed between 2,4,6,8,10,12-hexanitro-2,4,6,6,8,10,12-hexaazaisowurtzitane (CL-20) and nitropyrazole compounds were investigated using B3LYP-D3/6-311G(d,p) and B97-3c methods. CL-20 in these complexes was surrounded by methyl, nitro, and amino derivatives of 4-nitropyrazole. The influence of substituents on the molecular electrostatic potential distribution of nitropyrazoles was investigated to figure out the potential electrostatic interaction sites. For the complex, the O···H hydrogen bond was popular in the intermolecular interactions, and dispersion interaction played an essential role, especially in Cx/CL-20 multimolecular complexes. Trigger bond analysis showed that their strength increased upon the formation of intermolecular weak interactions. Nitro group charge calculations stated that the negative charge on almost all nitro groups showed a significant increase. Therefore, the sensitivity of CL-20 seemed to be lower than the original. In addition, the transfer of electron density between CL-20 and nitropyrzoles in complexes was investigated, revealing the influence of weak interactions on the electron density of CL-20.

Theoretical Study on the Effects of Hydrogen-Bonding and Molecule-Cation Interactions on the Sensitivity of HMX.

To assess the effects of weak interactions on the sensitivity of HMX, 11 complexes of HMX (where six of them are hydrogen-bonding complexes, and the other five are molecular-cation complexes) have been studied via quantum chemical treatment. The geometric and electronic structures were determined using DFT-B3LYP and MP2(full) methods with the 6-311++G(2df, 2p) and aug-cc-pVTZ basis sets. The changes of the bond dissociation energy (BDE) of the trigger bond (N-NO2 in HMX) and nitro group charge have been computed on the detailed consideration to access the sensitivity changes of HMX. The results indicate that upon complex forming, the BDE increases and the charge of nitro group turns more negative in complexes, suggesting that the strength of the N-NO2 trigger bond is enhanced and then the sensitivity of HMX is reduced. Atom-in-molecules analyses have also been carried out to understand the nature of intermolecular interactions and the strength of trigger bonds.

Structure, Physicochemical Properties, and Density Functional Theory Calculation of High-Energy-Density Materials Constructed with Intermolecular Interaction: Nitro Group Charge Determines Sensitivity

Four nitro-containing energetic compounds, cocrystal of AT·DNBA (1), salt of MA·DNSA (2), salt of AG·DNBA·H2O (3), and salt of DAT·DNSA H2O (4), are synthesized and structurally characterized based on supramolecular interactions (AT, 4-amino-1,2,4-triazole; DNBA, 3,5-dinitrobenzoic acid; MA, melamine; DNSA, 3,5-dinitrosalicylic acid; AG, amino guanidine; DAT, 3,5-diamino-1,2,4-triazole). The physicochemical properties of the compounds are theoretically and experimentally investigated in detail. The optimized structures, molecular total energies, frontier orbit energies, and charge densities of 1–4 are calculated by theoretical methods. The experimental results indicate that all compounds exhibit good thermostability and low sensitivity. It is worth noting that the values of impact sensitivity are measured to be 30, >40, 38, and >40 J for 1, 2, 3, and 4, respectively, which correspond well to the order of nitro group charge (QNitro) calculated by density functional theory. The detonation performances of 1–4 are discussed; in particular, 1 and 2 exhibit heats of detonation (2.191 kcal g–1 for 1 and 2.214 kcal g–1 for 2) superior to those of classical nitro-rich compounds. In addition, the nonisothermal thermokinetic parameters are obtained by Kissinger and Ozawa methods, and the standard molar enthalpies of formation are calculated from the determination of constant volume combustion energies.

Theoretical study of solvent effects on RDX crystal quality and sensitivity using an implicit solvation model.

Density functional theory calculations using an SMD model were performed to investigate the effect of solvents (cyclohexanone, acetone, dimethyl formamide and dimethyl sulphoxide) on the crystal quality and sensitivity of RDX. The results indicate that the N-N bond length of the RDX molecule in solvents differs clearly from that in gas phase. The solvent effect on bond and dihedral angles of RDX molecule is small, however, the RDX molecule still maintains the AEE configuration. Natural population analysis shows that, due to solvation effects, RDX O atoms attract more electrons in solvents than in gas phase, while more positive charge distributes to the molecular skeleton. The calculations of N-NO2 bond BDE and nitro group charge as well as surface electrostatic potential parameters reveal that the solvent effect may be helpful to reduce the sensitivity of RDX, but this effect has an upper limit. Finally, it can be predicted qualitatively that the crystal quality of RDX crystallized from cyclohexanone and dimethyl sulphoxide will be higher than that from acetone and dimethyl formamide. Experimental results support these theoretical predictions.

A B3LYP AND MP2(FULL) THEORETICAL INVESTIGATION INTO THEC–NO2BOND STRENGTH UPON THE FORMATION OF HF ORNa+COMPLEX INVOLVING THE NITRO GROUP OF NITRO-1,2,4-TRIAZOLE

The change of bond dissociation energy (ΔBDE) in the C–NO2bond upon the formation of the intermolecular hydrogen-bonding or molecule-cation interaction between the nitro group of seven kinds of nitro-1,2,4-triazoles and HF or Na+was investigated using the B3LYP and MP2(full) methods with the 6-311++G**, 6-311++G(2df, 2p) and aug-cc-pVTZ basis sets. The C–NO2bond strength was enhanced and the charge of nitro group turned more negative in complex in comparison with those in isolated nitro-1,2,4-triazole molecule. The increment of the C–NO2BDEs correlated well with the H-bonding interaction energy or molecule-cation interaction energy. The analysis of AIM, NBO and electron density shifts showed that the electron density shifted toward the C–NO2bond upon complex formation, leading to the strengthened C–NO2bond and the possibly reduced explosive sensitivity. The ΔBDE of the C–NO2bond in the Na+complex is far larger greater than that in the corresponding HF system. Thus, introducing cation into the structure of the nitrotriazole might be more efficacious to reduce explosive sensitivity than the formation of the intermolecular hydrogen-bonded complex.

A QSPR Model for Prediction of the Impact Sensitivities of some Nitro Compounds

The impact sensitivity is a very important property for indicating the safety, reliability and stability of high-energy-density materials (HEDM). A quantitative structure-property relationship (QSPR) study was used for prediction of impact sensitivity of some nitro compounds. Employing the square of nitro group charge (QNO22) and OB100as the parameters, a good QSPR model was built for predicting H50of two sorts of nitro compounds. The predictive ability of the model was assessed by leave-one-out cross-validation method. The cross-validation results shows that the model is significant and stable, and its predicted accuracy is within 0.21 m. This quantitative model may be a useful tool for the design of HEDM.

A B3LYP and MP2(full) theoretical investigation into the strength of the C–NO2 bond upon the formation of the intermolecular hydrogen-bonding interaction between HF and the nitro group of nitrotriazole or its methyl derivatives

The changes of bond dissociation energy (BDE) in the C-NO(2) bond and nitro group charge upon the formation of the intermolecular hydrogen-bonding interaction between HF and the nitro group of 14 kinds of nitrotriazoles or methyl derivatives were investigated using the B3LYP and MP2(full) methods with the 6-311++G**, 6-311++G(2df,2p) and aug-cc-pVTZ basis sets. The strength of the C-NO(2) bond was enhanced and the charge of nitro group turned more negative in complex in comparison with those in isolated nitrotriazole molecule. The increment of the C-NO(2) bond dissociation energies correlated well with the intermolecular H-bonding interaction energies. Electron density shifts analyses showed that the electron density shifted toward the C-NO(2) bond upon complex formation, leading to the strengthened C-NO(2) bond and the possibly reduced explosive sensitivity.

A B3LYP and MP2(full) theoretical investigation into the strength of the C-NO2 bond upon the formation of the molecule-cation interaction between Na+ and the nitro group of nitrotriazole or its methyl derivatives

The changes of bond dissociation energy (BDE) in the C-NO2 bond and nitro group charge upon the formation of the molecule-cation interaction between Na+ and the nitro group of 14 kinds of nitrotriazoles or methyl derivatives were investigated using the B3LYP and MP2(full) methods with the 6-311++G**, 6-311++G(2df,2p) and aug-cc-pVTZ basis sets. The strength of the C-NO2 bond was enhanced in comparison with that in the isolated nitrotriazole molecule upon the formation of molecule-cation interaction. The increment of the C-NO2 bond dissociation energy (ΔBDE) correlated well with the molecule-cation interaction energy. Electron density shifts analysis showed that the electron density shifted toward the C-NO2 bond upon complex formation, leading to the strengthened C-NO2 bond and the possibly reduced explosive sensitivity.