High-pressure stability of 1,1-diamino-2,2-dinitroethene (FOX-7): H/D isotope effect

Tao, Yuchuan; Dreger, Zbigniew A.; Gupta, Y. M.

doi:10.1016/j.cplett.2015.02.014

Cited by 10 publications

(9 citation statements)

References 26 publications

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“…1,1-Diamino-2,2-dinitroethene (DADNE or FOX-7) is one of the most promising insensitive HE crystals, with performance comparable to cyclotrimethylenetrinitramine (RDX). − FOX-7 has a relatively simple molecular structure, and its molecular and crystalline characteristics are similar to those of other known IHE crystals, including triaminotrinitrobenzene (TATB). , Thus, FOX-7 is an attractive prototype IHE crystal. Since its synthesis in 1998, considerable experimental efforts have been made to understand its crystal structures at extreme pressures and temperatures. − It was reported that the ambient structure of FOX-7, α phase (monoclinic, P 2 1 / n ), can transform to three HT (β, γ, and δ) − and two HP (α′ and ε) − phases. The crystal structures of HT, ambient pressure, phases β (>386 K, orthorhombic, P 2 1 2 1 2 1 ), and γ (>446 K, monoclinic, P 2 1 / n ) have been determined, but the δ phase (>483 K) structure remains unresolved …”

Section: Introductionmentioning

confidence: 99%

“…The α′ phase was indicated to have the same space group as the α phase . However, the ε-phase crystal structure has not been determined, despite considerable experimental − and computational efforts. ,− Significant changes in the optical spectra − and X-ray , and neutron powder diffraction patterns have suggested a substantial structural transformation. It was speculated that the ε phase can be amorphous or partially decomposed or assume plane layers .…”

Section: Introductionmentioning

confidence: 99%

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High-Pressure Crystal Structures of an Insensitive Energetic Crystal: 1,1-Diamino-2,2-dinitroethene

Dreger

Сташ

et al. 2016

J. Phys. Chem. C

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Understanding the insensitivity/stability of insensitive high explosive crystals requires detailed structural information at high pressures and high temperatures of interest. Synchrotron single-crystal X-ray diffraction experiments were used to determine the high-pressure structures of 1,1-diamino-2,2-dinitroethene (FOX-7), a prototypical insensitive high explosive. The phase transition around 4.5 GPa was investigated and the structures were determined at 4.27 GPa (α′ phase) and 5.9 GPa (ε phase). The α′ phase (monoclinic, P2 1 /n), structurally indistinguishable from the ambient α phase, transforms to the new ε phase (triclinic, P1). The most notable features of the ε phase, compared to those of the α′ phase, are formation of planar layers and flattening of molecules. Density functional theory (DFT-D2) calculations complemented the experimental results. The results presented here are important for understanding the molecular and crystalline attributes governing the high-pressure insensitivity/stability of insensitive high explosive crystals.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

High-Pressure Crystal Structures of an Insensitive Energetic Crystal: 1,1-Diamino-2,2-dinitroethene

Dreger

Сташ

et al. 2016

J. Phys. Chem. C

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“…1,1-Diamino-2,2-dinitroethene (C 2 (NO 2 NH 2 ) 2 , FOX-7, or DADNE) is an extremely promising insensitive high-explosive (IHE) crystal with excellent performance, low sensitivity to initiation, and a relatively simple molecular structure. − Because of these attractive characteristics, FOX-7 is viewed as a prototypical IHE crystal, and there have been considerable efforts to identify and understand its microscopic response at pressure and temperature conditions relevant to its initiation. − In particular, detailed knowledge of the high-pressure response is essential for understanding its structural and chemical stability/insensitivity in terms of the relevant molecular and crystalline processes. Additionally, determination of the pressure dependence of the lattice parameters is required to develop accurate equation of state (EOS) models for describing the continuum response of FOX-7.…”

Section: Introductionmentioning

confidence: 99%

High-Pressure Structural Response of an Insensitive Energetic Crystal: 1,1-Diamino-2,2-dinitroethene (FOX-7)

Dreger

Сташ

et al. 2016

J. Phys. Chem. C

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High-pressure structural response of an insensitive energetic crystal1,1-diamino-2,2-dinitroethene (FOX-7)was examined to gain insight into its structural and chemical stability and to obtain isothermal compression data. Using synchrotron single-crystal X-ray diffraction measurements, details of pressure-induced structural changes to 12.8 GPa were determined across three FOX-7 phases: α (P2 1 /n), α′ (P2 1 /n), and ε (P1). We found that the C−NO 2 bond is the most compressible chemical bond, and high pressure significantly reduces and homogenizes the length of H bonds in the hydrogen-bond network. The α′−ε phase transition, at 4.5 GPa, significantly affects all molecular and crystal properties, whereas the α−α′ transition, at 2 GPa, is associated with subtle molecular and intermolecular changes. Anisotropic compressibility was observed over the entire pressure range, consistent with the layered structure of the crystal. The equation-of-state parameters were obtained using the third-order Birch− Murnaghan equation below and above the α′−ε phase transition. It is shown that dispersion-corrected DFT-D calculations reproduce well pressure-induced changes in the unit cell parameters. The findings of this work provide new insights into the molecular and structural mechanisms governing the high-pressure stability/insensitivity of insensitive energetic crystals.

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“…Here, we report on the phase diagram and decomposition of single crystals of 1,1-diamino-2,2-dinitroethene (FOX-7, C 2 (NO 2 ) 2 (NH 2 ) 2 ), an energetic material with excellent performance and low initiation sensitivity. − Because of these attractive characteristics, FOX-7 is viewed as a prototypical insensitive high explosive (IHE) and considerable experimental efforts have been made in the past to understand its polymorphic behavior at high pressures and temperatures. − …”

Section: Introductionmentioning

confidence: 99%

Phase Diagram and Decomposition of 1,1-Diamino-2,2-dinitroethene Single Crystals at High Pressures and Temperatures

2016

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The high-pressure–high-temperature (HP-HT) phase diagram and decomposition of 1,1-diamino-2,2-dinitroethene (FOX-7), central to understanding its stability and reactivity, were determined using optical spectroscopy and imaging measurements in hydrostatically compressed and heated single crystals. Boundaries between various FOX-7 phases (α, α′, β, γ, and ε) and melting/decomposition curves were established up to 10 GPa and 750 K. The main findings are (i) a triple point is observed between α, β, and γ phases ∼0.6 GPa and ∼535 K; (ii) the previously suggested δ phase is not a new phase but is a partly decomposed γ phase. (iii) the α–α′ transition takes place along an isobar, whereas the α′−ε transition pressure decreases with increasing temperature; and (iv) melting/decomposition temperatures increase rapidly with pressure, with an increase in the slope at the onset of the α′−ε transition. Our results differ from the recently reported HP-HT phase diagram for nonhydrostatically compressed polycrystalline FOX-7. In addition, the observed interplay between melting and decomposition suggests the suppression of melting with pressure. Our Fourier transform infrared measurements at different pressures to 3.5 GPa showed similar decomposition products, suggesting similar decomposition pathways irrespective of the pressure. The present results provide new insights into the structural and chemical stability of an important insensitive high explosive crystal under well-defined HP-HT conditions.

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High-pressure stability of 1,1-diamino-2,2-dinitroethene (FOX-7): H/D isotope effect

Cited by 10 publications

References 26 publications

High-Pressure Crystal Structures of an Insensitive Energetic Crystal: 1,1-Diamino-2,2-dinitroethene

High-Pressure Crystal Structures of an Insensitive Energetic Crystal: 1,1-Diamino-2,2-dinitroethene

High-Pressure Structural Response of an Insensitive Energetic Crystal: 1,1-Diamino-2,2-dinitroethene (FOX-7)

Phase Diagram and Decomposition of 1,1-Diamino-2,2-dinitroethene Single Crystals at High Pressures and Temperatures

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