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Density functional theory calculation was performed to investigate the intermolecular interactions, thermodynamic properties, crystal structure, and detonation performance of CL-20 (2,4,6,8,10,12-hexanitrohexaazaisowurtzitane)/TEX (4,10-dinitro-2,6,8,12-tetraoxa-4,10-diaza-tetracyclododecane) cocrystal explosive. The results of natural bond orbital (NBO) and atoms in molecules analysis show that unconventional CH ... O type hydrogen bonds and dispersion force are the main driving forces for the cocrystal formation. Monte Carlo simulation was employed to predict the crystal structure of the CL-20/TEX cocrystal. The cocrystal is most likely to crystallize in a monoclinic system (space group C2/C), with cell parameters a = 40.62 [Angstrom], b = 7.35 [Angstrom], c = 41.36 [Angstrom], and [beta] = 157.38[degrees]. Based on crystal density, chemical energy, and heat of formations, detonation performance was calculated using Kamlet-Jacobs formulas. Detonation velocity and pressure of the CL-20/TEX cocrystal are higher than those of TEX but a litter lower than those of CL-20. Bond dissociation energy analysis shows that the cocrystal is thermal stable and meets the requirement of high energy density materials. Key words: CL-20, TEX, cocrystal, intermolecular interaction, DFT, detonation performance, sensitivity. Au moyen de la theorie de la fonctionnelle de la densite, nous avons effectue des calculs afin d'etudier les interactions intermoleculaires, les proprietes thermodynamiques, la structure cristalline et la performance de detonation de l'explosif constitue du cocristal de CL-20 (2,4,6,8,10,12-hexanitrohexaaza-isowurtzitane) et de TEX (4,10-dinitro-2,6,8,12-tetraoxa-4,10diazatetracyclododecane). Les resultats des calculs selon la theorie des orbitales naturelles de liaison et de la theorie quantique des atomes dans les molecules indiquent que des liaisons hydrogene non conventionnelles de type CH ... O et la force de dispersion sont les principales forces motrices de la formation du cocristal. Nous avons employe une simulation de Monte Carlo afin de predire la structure du cocristal CL-20/TEX. L'hypothese la plus probable voudrait que le cocristal se forme selon un systeme monoclinique (groupe spatial C2/C), dont les parametres de cellule sont a = 40,62 [Angstrom], b = 7,35 [Angstrom], c = 41,36 et [beta] = 157,38[degrees]. En tenant compte de la densite du cristal, de l'energie chimique et de la chaleur de formation, nous avons calcule la performance de detonation a l'aide des formules de Kamlet-Jacobs. La vitesse et la pression de detonation du cocristal CL-20/TEX sont plus elevees que celles du TEX, mais legerement plus basses que celles du CL-20. L'analyse des energies de dissociation des liaisons indique que le cocristal est thermiquement stable et repond aux exigences des matieres a haute densite energetique. [Traduit par la Redaction] Mots-cles: CL-20, TEX, cocristal, interaction intermoleculaire, DFT, performance de detonation, sensibilite., Introduction In recent years, cocrystallization has emerged as a promising way to modify the properties of existing explosives. (1-3) Compared with the traditional methods of modification, cocrystallization in most cases [...]

Although lithium-sulfur (Li-S) batteries are widely regarded as one of the most promising next-generation high energy density storage systems, their large-scale applications are seriously impeded by rapid capacity fading and poor Coulombic efficiency owing to the shuttling of lithium polysulfides (LiPSs) and irreversible discharge product Li2S. Here, by means of first principles calculations, we studied defective black phosphorene (BP) as a host material to realize high-performance Li-S batteries, including Stone Wales [SW(55-77)], single, and double vacancy [SV(5-9) and DV(5-9-5)] defects. Our results demonstrate that while BP has moderate adsorption energies towards LiPSs, the presence of defects could enhance the adsorption strength between LiPSs and BP because of increased charge transfer. Particularly, defective BP could strike a good balance between adsorption energy and integrity of LiPSs, which is beneficial to prevent the shuttling of LiPSs. Moreover, during the lithiation process, defective BP not only has narrow bandgaps but also decreases the dissociation energy of Li2S, facilitating the catalytic oxidation of Li2S back to sulfur. Therefore, it is highly desirable to fabricate defective BP to improve the reversible capacity and cycle stability of Li-S batteries. [ABSTRACT FROM AUTHOR]

An investigation on the structural, electronic, thermodynamic, and mechanical properties of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)/2-methylpyridine-N-oxide (MPNO) cocrystal was carried out from 0 to 100 GPa by using a dispersion-corrected density functional theory (DFT-D) method. Our calculated crystal structure is in excellent agreement with experimental results at ambient pressure. Based on the analysis of lattice parameters, lattice angles, bond lengths, bond angles, and dihedral angles under high pressure, we observe that HMX molecules in the cocrystal bulk are seriously distorted but MPNO molecules remain relatively unchanged. Hydrogen bond lengths are greatly shortened under high pressure. In addition, with the increase in pressure, the bandgap decreases gradually. However, it increases suddenly at 70 GPa. Some important hydrogen bonds between HMX and MPNO are also observed in the density of states spectrum. According to the thermodynamic analysis, this cocrystal is more easily prepared under low pressure. Finally, we characterized its mechanical properties and the results show that this cocrystal is malleable in nature. We expect that this research can provide a fundamental basis for further HMX cocrystal design and preparation. [ABSTRACT FROM PUBLISHER]

A novel 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX)/pyridine-N-oxide (PNO) cocrystal at 1:1 molar ratio was synthesized by a solvent evaporation method, and its crystal structure was determined using X-ray diffraction (XRD). It crystallizes in the orthorhombic system with thePbcn space group and cell parametersa = 12.712(3)Å,b = 9.315(3)Å,c = 12.909(3)Å. In addition, detonation performance of this cocrystal was estimated. The predicted detonation velocity and detonation pressure of this cocrystal are 7.47 km/s and 23.20 GPa, respectively, suggesting that it is less powerful than β-HMX. Finally, density functional theory, involving binding energy, atoms in molecule (AIM) theory, natural bond orbital (NBO) analysis, band structure, and density of states, was adopted to characterize the driving forces for the formation of this cocrystal. The results show that driving forces are dominated by the interactions between O atoms of PNO and methylene groups of HMX. It is expected that this research provides some bases for further HMX cocrystal design and preparation. [ABSTRACT FROM PUBLISHER]

In this work, properties of polynitro-bridged pyridine derivatives were systemically studied at the B3LYP/6-31G(d) level. Gas-phase heats of formation (HOFs) for the designed compounds were calculated using isodesmic reactions, and their solid-phase HOFs were estimated using the Politzer approach. All designed compounds possess large solid-phase HOFs, larger than 700 kJ/mol. Based on the predicted crystal densities, solid-phase HOFs, and chemical energies, detonation properties were evaluated by means of Kamlet-Jacobs empirical equations. The results show that detonation velocities and pressures of all of the designed compounds are above 9.30 km/s and 40.00 GPa, respectively. In addition, bond dissociation energy (BDE) was employed to investigate their thermal stability. Considering solid-phase HOFs, detonation performance, and thermal stability, most of the designed compounds meet the requirements of high energy density materials (HEDMs). [ABSTRACT FROM PUBLISHER]

Previous studies have shown that the design of cocrystal explosives is one of the most promising approaches to decrease the sensitivity and maintain the detonation performance of existing explosives. As is well-known, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is a high energy density material (HEDM). But the application of HMX is limited, due to its high sensitivity. Thus, an insensitive explosive 5-nitro-1,2,4-triazol-3-one (NTO) is proposed as a cocrystal former (CCF) to cocrystallize with HMX in the present work. The binding energies, heat of formations (HOFs), thermodynamic properties, atoms in molecules, and natural bond orbital analysis of four HMX/NTO complexes have been calculated using density functional theory methods, including meta-hybrid functional (M062X) and dispersion-corrected density functionals (B97D, ωB97XD). In addition, the crystal structure of HMX/NTO cocrystal has been investigated using Monte Carlo simulation and first principles methods. The HMX/NTO cocrystal is most likely to crystallize in triclinic crystal system with P 1 space group, and corresponding cell parameters are Z = 2, a = 9.06 Å, b = 8.19 Å, c = 10.27 Å, α = 81.94°, β = 98.42°, γ = 82.03°, and ρ = 1.92 g/cm3. The detonation velocity and detonation pressure of HMX/NTO cocrystal are 8.73 km/s and 35.14 GPa, respectively, a little lower than those of HMX. Finally, bond dissociation energies (BDEs) of the weakest trigger bond in HMX/NTO complexes are calculated. The results show that HMX/NTO complexes are thermally stable and meet the thermal requirement of HEDMs (BDE > 120 kJ/mol). © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In order to explore the mechanism of co-crystal explosive formation, styphnic/1,4-dioxane solvate was prepared by solvent evaporation method. This solvate structure was characterized by single crystal X-ray diffraction. Structural analysis shows that 0 in 1,4-dioxane forms --OH ⋯ 0 strong hydrogen bond with OH in styphnic. Moreover, H in 1,4-dioxane forms CH ⋯ 0--NO weak intermolecular interaction with nitro group in styphnic. These two kinds of interactions are the main driving force for solvate composing. The Mulliken charge and density of state of both styphnic and styphnic/1,4-dioxane solvate are calculated. The result shows that the nitro group has more negative charge in the solvate than that in the pure styphnate. P orbital plays an important role in the buildup of the solvate and H in styphnate hybridizes with O in 1, 4-dioxane. [ABSTRACT FROM AUTHOR]

Six models of cyclotetramethylene tetranitramine (HMX)/1, 1-diamino-2. 2-dinitroethylene (FOX-7) co-crystal were constructed based on the main growth faces of HMX crystal and the hydrogen bond rules of co-crystal formation. The probability of HMX/FOX-7 co-crystal formation was investigated using the molecular dynamics (MD) method. The distributions of bond length, angle, and dihedral angle were calculated during MD. As a result, a serious distortion was observed. The radical distribution function (RDF) was used to study the acting force between oxygen atoms in HMX and hydrogen atoms in FOX-7 or hydrogen atoms in HMX and oxygen atoms in FOX-7, which indicates that there are strong hydrogen bonds and Van Der Waals forces between HMX and FOX-7. Binding energies and X-ray powder diffraction (XRD) were calculated on the basis of the final HMX/FOX-7 co-crystal structure. The results show that the orders of binding energies of the six co-crystal models are Eb (020) > Eb (100) > Eb (randomness) > Eb (11̄1) > Eb(10̄2) > Eb (011), and the XRD peaks of six co-crystal models are quite different from pure HMX or FOX-7. In view of the research on crystal growth morphology, binding energy and RDF, the model of HMX molecular substituted by FOX-7 on the surface (11Six models of cyclotetramethylene tetranitramine (HMX)/l , l-diamino-2. 2-dinitroethylene (FOX-7) co-crystal were constructed based on the main growth faces of HMX crystal and the hydrogen bond rules of co-crystal formation. The probability of HMX/FOX-7 co-crystal formation was investigated using the molecular dynamics (MD) method. The distributions of bond length, angle, and dihedral angle were calculated during MD. As a result, a serious distortion was observed. The radical distribution function (RDF) was used to study the acting force between oxygen atoms in HMX and hydrogen atoms in FOX-7 or hydrogen atoms in HMX and oxygen atoms in FOX-7 , which indicates that there are strong hydrogen bonds and Van Der Waals forces between HMX and FOX-7. Binding energies and X-ray powder diffraction (XRD) were calculated on the basis of the final HMX/FOX-7 co-crystal structure. The results show that the orders of binding energies of the six co-crystal models are Eb (020) > Eb (100) > Eb (randomness) > Eb (ll̄l) > Eb(10̄2) > Eb (011), and the XRD peaks of six co-crystal models are quite different from pure HMX or FOX-7. In view of the research on crystal growth morphology, binding energy and RDF, the model of HMX molecular substituted by FOX-7 on the surface (11̄1) of HMX is more liable to form. 1) of HMX is more liable to form. [ABSTRACT FROM AUTHOR]

Semiconductor bridge (SCB) was utilized to ignite energetic materials with thin film discharge and characterized of low input energy, high safety and logic control possibility. SCB discharge was diagnosticated with atomic emission spectroscopy. Firstly, discharge temperature was acquired with copper atom spectral lines 510.5 and 521.8 nm, and electron density was calculated with silicon atom spectral line 390.5 nm and corresponding ion line 413.0 nm. As for resistance 1.0 omega of SCB with the discharge voltage of 20 V and capacity of 47 microF, its discharge temperature was about 2 500-4 300 K and electron density 10(16) cm(-3). Meanwhile, the temperature and density V(s) time distributions were acquired simultaneously. And then with the diagnosis results, the discharge behaviors of two sorts of SCB were judged according to plasma space-dimension and time-dimension restrictions. This research set up an efficient technique for the diagnosis of transient small-size discharge behavior and provided instructions for the design of SCB and discharge condition.

Electron temperature is one of the important parameters of plasma. It is very difficult to measure the electron temperature exactly and instantly owing to its complexity during discharge. As a plasma diagnostics technique, emission spectroscopy is widely applied in the study and diagnosis of any kind of plasma, because of its simple instrument system, noninterference of measurement, high sensitivity and fast responsibility. In the present paper, some methods for plasma electron temperature diagnosis, such as two lines method, multiline slope method, isoelectronic line method, Saha-Boltzmann equation, absolute intensity method, were introduced. And the applications of these methods were reviewed to provide reference for choosing appropriate methods in practice.