Potential High Energy Density Materials Research Articles

Pressure-Induced High-Energy-Density BeN6 Materials: First-Principles study

Recently, the use of polymeric nitrogen in the search for high-energy–density materials (HEDMs) has attracted widespread attention. However, synthesizing polymeric nitrogen materials is quite challenging; for instance, the synthesis of cubic gauche nitrogen requires a high pressure of 110 GPa. Previous theoretical predictions and experiments have shown that adding alkaline earth metals as cationic ligands can stabilize polymeric nitrogen and reduce the synthesis pressure. Using the USPEX structural prediction code and first-principles calculations, this study predicted 2 new nitrogen salt with nitrogen contents up to 89.80 %, namely α-BeN6 and β-BeN6, with their unique nitrogen chain structures, have energy densities as high as 3.32 and 3.59 kJ/g, respectively. The exceptional explosive properties reveal these two BeN6 are potential HEDMs. In addition, α-BeN6 is a direct bandgap semiconductor.

Polymethylenetetrazole: Synthesis, Characterization, and Energetic Properties.

The tetrazole moiety remains one of the most interesting scaffolds in the development of new high-energy density materials (HEDMs) because of its desired characteristics, such as high nitrogen content and heat of formation (HOF). The combination of several heterocycles with high HOF seems to be a promising strategy for obtaining energetic materials with superior properties. Herein, we report the synthesis and characterization of a tetrazole polymer, polymethylenetetrazole (PMT), as a potential HEDM. The compound was characterized using NMR, IR, and Raman spectroscopy. Its weight average molecular mass was obtained by static light scattering (SLS), and its physical properties by powder XRD analysis. The density, sensitivity to friction (FS), and impact (IS) of the compound were determined as well. The results of the thermal and energetic properties of PMT suggest that this polymer could be an insensitive explosive.

Theoretical study of a series of 1,2-diazete based trinitromethyl derivatives as potential energetic compounds.

Explosive properties of novel potential high energy density materials of a series of 1,2-diazete-based molecules with trinitromethyl functional group were investigated computationally. All the sixty seven molecules were optimised to obtain their molecular geometries and electronic structures. Electrostatic potential analysis was also carried out in the determination of different parameters. The calculations indicate that the majority of the compounds have high positive heat of formations, high density and good detonation performance greater than that of traditional energetic materials like RDX and HMX. They are also having comparable values of impact sensitivity. These features promise their potential to be used as energetic materials for future applications. Most of the designed molecules are having high positive oxygen balance values so that the study of these molecules can also be extended as potential candidates for oxidisers in solid propellants. Optimisation and vibrational frequency analysis of the studied molecules were done with density functional theory using B3LYP/aug-cc-pVDZ as the basis set to zero imaginary frequencies using Gaussian 09. Electrostatic potential analysis were carried using the Multiwfn program.

Theoretical investigation on heats of formation, detonation properties and sensitivities of TANPy based energetic materials

A series of 2,4,6-triamino-3,5-dinitropyridine (TANPy) based energetic compounds were designed and optimized at the B3LYP/6-311G (d,p). The results show that all the designed compounds have high positive heats of formation, and the tetrazole ring/–N3 was an beneficial combination to increase the heats of formation. The introduction of furazan-furazan/-C(NO2)3/–CH(NO2)2 combination was effective to improve the densities and detonation properties while the furazan-furazan or furazan-tetrazine rings was beneficial to improving the values of heats of detonation. Considering the detonation properties and sensitivities, compounds D2, E2, F2 were finally screened as potential high energy density materials and their physicochemical properties were fully investigated.

One-Dimensional Non-coplanar Nitrogen Chains in Manganese Tetranitride under High Pressure.

Transition metal nitrides have great potential applications as incompressible and high energy density materials. Various polymeric nitrogen structures significantly affect their properties, contributing to their complex bonding modes and coordination conditions. Herein, we first report a new manganese polynitride MnN4 with bifacial trans-cis [N4]n chains by treating with high-pressure and high-temperature conditions in a diamond anvil cell. Our experiments reveal that MnN4 has a P-1 symmetry and could stabilize in the pressure range of 56-127 GPa. Detailed pressure-volume data and calculations of this phase indicate that MnN4 is a potential hard (255 GPa) and high energy density (2.97 kJ/g) material. The asymmetric interactions impel N1 and N4 atoms to hybridize to sp2-3, which causes distortions of [N4]n chains. This work discovers a new polynitride material, fills the gap for the study of manganese polynitride under high pressure, and offers some new insights into the formation of polymeric nitrogen structures.

New carbon–nitrogen–oxygen compounds as high energy density materials

Molecular crystals are complex systems exhibiting various crystal structures, and accurately modeling the crystal structures is essential for understanding their physical behaviors under high pressure. Here, we perform an extensive structure search of ternary carbon-nitrogen-oxygen (CNO) compound under high pressure with the CALYPSO method and first principles calculations, and successfully identify three polymeric CNO compounds with Pbam, C2/m and symmetries under 100 GPa. More interestingly, these structures are also dynamically stable at ambient pressure, and are potential high energy density materials (HEDMs). The energy densities of Pbam, C2/m and phases of CNO are about 2.30 kJ/g, 1.37 kJ/g and 2.70 kJ/g, respectively, with the decompositions of graphitic carbon and molecular carbon dioxide and α-N (molecular N2) at ambient pressure. The present results provide in-depth insights into the structural evolution and physical properties of CNO compounds under high pressures, which offer crucial insights for designs and syntheses of novel HEDMs.

Novel high-pressure phases of nitrogen-rich Y-N compounds.

Five new high-pressure phases (I4̄3d-Y4N3, R3c-Y2N3, P1̄-II-YN4, P1̄-YN6, and P31c-YN8) are proposed by the crystal structure prediction. A series of polynitrogen forms were achieved in the nitrogen-rich Y-N compounds, including diatomic N2, an isolated N8 chain, an infinite N chain with an N6 unit, and an infinite N layer with bent N18 rings. The high energy densities of P1̄-II-YN4 (1.98 kJ g-1), P1̄-YN6 (2.35 kJ g-1), and P31c-YN8 (3.77 kJ g-1) make them potential high energy density materials. More importantly, P1̄-II-YN4, P1̄-YN6, and P31c-YN8 exhibit excellent explosive performance, with detonation pressures 4-8 times that of TNT (19 GPa) and detonation velocities 1-2 times that of TNT (6.90 km s-1). The electronic structure and bonding properties show that the high stability of Y-N compounds originates from the strong N-N covalent bond and the weak Y-N ionic bond interaction. The increase in the transferred charge quantity as the pressure decreased is more conducive to stabilizing the polymeric nitrogen structure, which leads to the metastable properties of P1̄-II-YN4 and P1̄-YN6 under ambient conditions. Finally, the infrared (IR) spectra of P1̄-II-YN4, P1̄-YN6, and P31c-YN8 are calculated to provide a reference in experimental synthesis.

Synthesis, Characterization and DFT Study of a New Family of High-Energy Compounds Based on s-Triazine, Carborane and Tetrazoles.

An efficient one-pot synthesis of carborane-containing high-energy compounds was developed via the exploration of carbon-halogen bond functionalization strategies in commercially available 2,4,6-trichloro-1,3,5-triazine. The synthetic pathway first included the substitution of two chlorine atoms in s-triazine with 5-R-tetrazoles (R = H, Me, Et) units to form disubstituted tetrazolyl 1,3,5-triazines followed by the sequential substitution of the remaining chlorine atom in 1,3,5-triazine with carborane N- or S-nucleophiles. All new compounds were characterized by IR- and NMR spectroscopy. The structure of four new compounds was confirmed by single crystal X-ray diffraction analysis. The density functional theory method (DFT B3LYP/6-311 + G*) was used to study the geometrical structures, enthalpies of formation (EOFs), energetic properties and highest occupied and lowest unoccupied molecular orbital (HOMO and LUMO) energies and the detonation properties of synthesized compounds. The DFT calculation revealed compounds processing the maximum value of the detonation velocity or the maximum value of the detonation pressure. Theoretical terahertz frequencies for potential high-energy density materials (HEDMs) were computed, which allow the opportunity for the remote detection of these compounds.

Polymerization of nitrogen in two theoretically predicted high-energy compounds ScN6 and ScN7 under modest pressure

Materials under high pressure usually exhibit unique chemical and physical properties. Polynitrogen compounds have received widespread attention as potential high energy density materials. This paper uses CALYPSO crystal structure prediction method to study the structures of ScN6 and ScN7 in 0–100 GPa. Theoretical calculations show that ScN6 is thermodynamically stable above 80 GPa, while ScN7 is thermodynamically stable from 30 GPa to 90 GPa. Furthermore, ScN7 is metastable under ambient conditions, demonstrating that it can be quenched to ambient conditions after high pressure synthesis. The P -ScN6 is a three-dimensional extended fold multi-nitrogen network, and the P -ScN7 contains a five-membered ring and a curved N4 molecular unit. Both P -ScN6 and P -ScN7 contain a lot of N–N single bonds and N=N double bonds. The energy densities of P -ScN6 and P -ScN7 are 3.97 kJ g−1 and 3.12 kJ g−1, respectively. The detonation velocity and detonation pressure of the P -ScN6 phase and P -ScN7 phase are also higher than that of TNT. Excellent energy storage properties and detonation performance show that they can be used as potential high-energy materials. These results opened up a new way for the synthesis of nitrogen-rich compounds.

Density functional theory investigation of triazole substituted nitro borazine derivatives as high energy density material

This work involves Density Functional Theory (DFT) investigation for prediction of nitrogen enriched boron based heterocyclic molecules for potential application as high energy density materials (HEDMs). The development of environment benign energetic materials as propellants, explosives, construction, military purposes and safety equipments are of immense interest. Boron based heterocyclic molecules with high nitrogen content have remarkable explosive properties. They are safe to the environment as their decomposition produces safe nitrogen gas instead of toxic hydrocarbons. In this work we have performed DFT calculations of thermodynamic properties and explosive characteristics of triazole substituted nitro borazine derivatives to assess their role as possible HEDMs. Effects of substitution of triazole group along boron atom and nitrogen atom have been investigated. Energetic properties that are important in deciding the explosive characteristics have been computed. Calculation of heat of formation through isodesmic reaction, detonation properties, heat of combustion etc. has been carried out. Further, crystal density, chemical stability and impact sensitivity have been analyzed. The designed molecules have nitrogen content of more than 48% and density in the range of 1.74–1.78 g/cm3. Impact sensitivity of the molecules indicates them as highly insensitive towards impact. Computed results in our investigation suggests that substitution of triazole ring along boron atom of the nitro borazine derivatives could be a potential high energy density material.

Pressure-induced stability and polymeric nitrogen in alkaline earth metal N-rich nitrides (XN6, X = Ca, Sr and Ba): a first-principles study.

Multi-nitrogen or polynitrogen compounds can be used as potential high energy-density materials, so they have attracted great attention. Nitrogen can exist in alkaline earth metal nitrogen-rich (N-rich) compounds in the form of single or double bonds. In recent years, to explore N-rich compounds which are stable and easy to synthesize has become a new research direction. The N-rich compounds XN6 (X = Ca, Sr and Ba) have been reported under normal pressure. In order to find other stable crystal structures, we have performed XN6 (X = Ca, Sr and Ba) exploration under high pressure. We found that SrN6 has a new P1̄ phase at a pressure of 22 GPa and an infinite nitrogen chain structure, and BaN6 has a new C2/m phase at 110 GPa, with an N6 ring network structure. Further, we observed that the infinite nitrogen chain and the N6 ring network structure contain typical covalent bonds formed by the hybridization of the sp2 and sp3 orbitals of N, respectively. It is found that both SrN6 and BaN6 are semiconductor materials and the N-2p orbital plays an important role in the stability of the crystal structure for P1̄-SrN6 and C2/m-BaN6. Because of the polymerization of nitrogen in the two compounds and their stabilities under high pressure, they can be used as potential high energy-density materials. The research in this paper further promotes the understanding of alkaline earth metal N-rich compounds and provides new information and methods for the synthesis of alkaline earth metal N-rich compounds (XN6, X = Ca, Sr and Ba).

First principles investigation of electron correlation and Lifshitz transition within iron polynitrides

Metal poly-nitrogen compounds are gaining great interests as potential high energy density materials. Several iron polynitrides have been recently synthesized and investigated under high pressure (2018 Nature Communications 9 2756). In this work the electron correlations within these iron poly-nitrogen compounds were self-consistently determined, benchmarked with those obtained from linear response approach. Along with the increase of the concentration of nitrogen, the Coulomb interaction strengths show a monotonic decrease, where FeN and FeN2 are antiferromagnetic and the others are ferromagnetic. Then the electron correlation is studied along with the pressure, where the electrons are more delocalized as pressure becomes higher. One electronic topological transition was found for FeN2, owing to a breaking of symmetry of spin and a transition of magnetism induced by a structural change. The band structure, densities of states, Fermi surface and absorption spectra were calculated and discussed.

Prediction of energetic properties of carboranyl tetrazoles based on DFT study

Compounds which are rich in boron and nitrogen have the potential to find application as high-energy material. In the present article quantum-chemical calculations (DFT B3LYP/6-311 + G*) of geometric and electronic structures, enthalpies of formation, highest occupied and lowest unoccupied molecular orbital (HOMO and LUMO) energies and the detonation properties of 22 molecules of carboranyl tetrazoles were carried out. The method of the estimation of enthalpies of formation of carboranyl tetrazoles based on full energies of the molecules and semi empirical parameters for solid carbon (graphite) and boron was proposed. The enthalpies of formation of carboranyl tetrazoles were evaluated. Theoretical terahertz frequencies for potential high-energy density materials (HEDMs) were computed which allows the opportunity for the remote detection of these compounds. According to the results of calculations the most promising HEDMs among studied compounds were found to be 9,12-bis(2-(5-phenyl-tetrazol-2-yl)propyl)-o-carborane; 9,10-bis(2-(5-phenyl-tetrazol-2-yl)propyl)-m-carborane; 5,5’-(butan-1,4-diyl)-{9,12-bis[2-(tetrazol-2-yl)prop-1-yl]-о-carborane}. Based on the calculated frontier molecular orbital energy gap these energetic materials are even less impact sensitive than classical diaminotrinitrobenzene (DATB) and trinitroaniline (TNA). These compounds are characterized by the maxima magnitudes of the evaluation of the enthalpies of formation (EOF) and can be considered as promising HEDMs as their EOF values are notably higher than those of well-known trinitrotoluene (TNT) and hexogen (RDX, Research Department eXplosive).

A Novel Synthesis, Characterization and Performances of 1,3,5‐Trinitro‐2,2‐bis(trifluoromethyl)‐1,3,5‐triazinane

AbstractA novel synthetic method of the 1, 3, 5‐trinitro‐2, 2‐bis(trifluoromethyl)‐1,3,5‐triazinane (2) has been successfully developed. In addition to IR, 1H 13C NMR and elemental analysis, compound 2 was characterized by 15N NMR and X‐ray single crystal diffraction. Due to the introduction of trifluoromethyl, the density of compound 2 is up to 2.04 g⋅cm−3 at 298 K, which is consistent with its crystal density (2.059 g⋅cm−3, 296(2) K). Compound 2 exhibits excellent detonation pressures and velocities (P, 45.6 GPa; vD, 9564 m⋅s−1), as good as exceptional impact and friction sensitivities(IS, 22.5 J; FS, >360 J). Some of these values are better than the current benchmark explosives, such as 1, 3, 5‐trinitrodihydro‐1, 3, 5‐triazine (RDX) and cyclo‐1, 3, 5, 7‐tetramethylenene‐2, 4, 6, 8‐tetranitramine (HMX).It is a potential high energy density material.

Theoretical Design and Screening Potential High Energy Density Materials: Combination of 1,2,4-oxadiazole and 1,3,4-oxadiazole Rings

Theoretical Design and Screening Potential High Energy Density Materials: Combination of 1,2,4-oxadiazole and 1,3,4-oxadiazole Rings

Assessing the Detonation Performance of New Tetrazole Base High Energy Density materials

AbstractTetrazole derivatives containing energetic groups can be considered as high energy density materials due to their high positive standard enthalpies of formation and high densities. The effects of two energetic groups −NO2 and −N3 as well as stabilizing group −NH2 and methyl group are investigated for assessment of detonation performance of 50 tetrazole derivatives where 12 derivatives have been synthesized. The velocities of detonation and detonation pressures are estimated on the basis of two new predictive methods, which require the condensed phase standard enthalpy of formation (ΔfH°c) and crystal density (ρ). Quantum mechanical and quantitative structure‐property relationship (QSPR) methods are used for calculation of ΔfH°c. In order to calculate the ρ values, the electrostatic potentials mapped onto the 0.001 a.u. isosurface of electron densities of isolated molecules is used. Detonation performances of tetrazole derivatives are compared to three common high explosives, i. e. TNT, RDX, and HMX. Among many tetrazole derivatives, four new tetrazole derivatives are introduced as new potential high energy density materials.

High-pressure behavior and Hirshfeld surface analysis of nitrogen-rich materials: triazido-s-triazine (TAT) and triazido-s-heptazine (TAH)

Triazido-s-triazine (TAT) and triazido-s-heptazine (TAH) are two kinds of effective nitrogen-rich precursors for carbon nitride nanomaterials and potential high-energy density materials. In this work, the high-pressure behavior (0–500 GPa) and Hirshfeld surface of crystalline TAT and TAH were studied in details to better compare and reveal their stabilities. Crystal and molecular structures of TAT and TAH largely changed with the increase in pressure. The distortion of rings happens at 171 GPa for TAT and 483 GPa for TAH. The azide/tetrazole (AZ/TZ) isomerization happens in crystalline TAT, and the tetrazole ring forms at 266 GPa for the first time, while this phenomenon has not been observed in crystalline TAH during the whole process. Hirshfeld surface analyses intuitively show that: (1) both compounds possess the planar conjugated molecular structures; (2) N…N nonbonding interactions contribute a lot to stabilize their crystal packings; and (3) TAH is much more resistant to high pressure and more stable than TAT. The systematic investigation gives a guidance to understand the physical and chemical behaviors of nitrogen-rich azidoheterocyclic materials.

Fe-N system at high pressure reveals a compound featuring polymeric nitrogen chains

Poly-nitrogen compounds have been considered as potential high energy density materials for a long time due to the large number of energetic N–N or N=N bonds. In most cases high nitrogen content and stability at ambient conditions are mutually exclusive, thereby making the synthesis of such materials challenging. One way to stabilize such compounds is the application of high pressure. Here, through a direct reaction between Fe and N2 in a laser-heated diamond anvil cell, we synthesize three ironnitrogen compounds Fe3N2, FeN2 and FeN4. Their crystal structures are revealed by single-crystal synchrotron X-ray diffraction. Fe3N2, synthesized at 50 GPa, is isostructural to chromium carbide Cr3C2. FeN2 has a marcasite structure type and features covalently bonded dinitrogen units in its crystal structure. FeN4, synthesized at 106 GPa, features polymeric nitrogen chains of [N42−]n units. Based on results of structural studies and theoretical analysis, [N42−]n units in this compound reveal catena-poly[tetraz-1-ene-1,4-diyl] anions.

Nitro derivatives of triazetidine: potential high energy density materials.

In a continuing effort to evaluate the properties of new possible high energy density materials, we have calculated the optimized geometries and thermodynamic properties of a series of nitro derivatives of triazetidine, c-CH2(NH)3. After evaluating approximately 50 different levels of NO2 substitution and conformations, we predict that several nitrotriazetidine compounds show some significantly desirable HEDM properties. Graphical abstract The triazetidine molecule, the parent structure for a series of new hypothetical high energy densitymaterials with various NO2 content.

Molecule and Synthesis Design of a Family of High Energy Density Materials Based on “565” Chemical Structure

AbstractA family of high energy density materials based on “565” chemical structure were designed and the spatial structure, heat of formation, detonation velocity, detonation pressure and sensitivity of each compound were investigated systematically by density functional theory. The results show that all the designed molecules possess high positive heat of formation (from 336.8 to 4135.7 kJ mol−1) and moderate detonation properties (detonation velocities range from 6.15 to 11.69 km s−1 and detonation pressures range from 16.4 to 68.28 GPa). Based on the values of detonation properties, impact sensitivities (range from 6.8 to 54.3 cm) and bond dissociation energies (range from 30.7 to 402.6 kJ mol−1), compounds A1, A2, A4 and B4 were selected as the potential high energy density materials. Then frontier molecular orbital, electrostatic potential on the surface and thermal dynamic parameters of these selected molecules were simulated to give a better understanding of their chemical and physical properties. Also, a reasonable synthetic path of the selected molecules were provided for further experimental synthesis and testing.