Phase Diagram of Hexahydro-1,3,5-trinitro-1,3,5-triazine Crystals at High Pressures and Temperatures

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

doi:10.1021/jp105226s

Cited by 91 publications

(127 citation statements)

References 21 publications

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“…2 The search for promising energetic materials has led to the discovery of a vast number of new energetic materials with increased performance, reduced sensitivity to external stimuli, and enhanced chemical and thermal stability 3,4 . One approach to improve materials' properties is to combine existing chemical entities to form either blends and/or polymorphic crystal forms 5,6 . Crystallization 7 is already having a tremendous impact on pharmaceuticals 8 and energetic materials, and it is poised to make a significant mark on other fields such as non-linear optics 9 , and organic electronics 10 .…”

Section: Introductionmentioning

confidence: 99%

Compressive Shear Reactive Molecular Dynamics Studies Indicating That Cocrystals of TNT/CL-20 Decrease Sensitivity

Guo

Goddard

et al. 2014

J. Phys. Chem. C

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To gain an atomistic-level understanding of how compounding the TNT and CL20 energetic materials into a TNT/CL-20 cocrystal might affect the sensitivity, we carried out the compressive--shear reactive molecular dynamics (CS-RMD) simulations. Comparing with the pure crystal of CL-20, we find that the co-crystal is much less sensitive. We find that the molecular origin of the energy barrier for anisotropic shear results from steric hindrance toward shearing of adjacent slip planes during shear deformation, which is decreased for the co-crystal. To compare the sensitivity for different crystals, we chose the shear slip system with lowest energy barrier as the most plausible one under external stresses for each crystal. Then we used the temperature rise and molecule decomposition as effective measures to distinguish sensitivities. Considering the criterion as number NO 2 fragments produced, we find that the cocrystal has lower shear-induced initiation sensitivity by ~70% under atmospheric pressure and ~46% under high pressure (~5 GPa) than CL-20. Based on the temperature increase rate, the cocrystal has initiation sensitivity lower by 22% under high pressure (~5 GPa) than CL-20. These results are consistent with available experimental results, further validating the CS-RD model for distinguishing between sensitive and insensitive materials rapidly (within a few picoseconds of MD).

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Section: Introductionmentioning

confidence: 99%

Compressive Shear Reactive Molecular Dynamics Studies Indicating That Cocrystals of TNT/CL-20 Decrease Sensitivity

Guo

Goddard

et al. 2014

J. Phys. Chem. C

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“…18 The Raman spectra of -RDX have also been reported. 19,20 A complementary approach to experiment is atomistic simulation, which provides an effective way to model the properties and structure of crystalline materials. The suitability of density functional theory (DFT) for studying energetic molecular materials has been reported in depth.…”

mentioning

confidence: 99%

Experimental and DFT-D Studies of the Molecular Organic Energetic Material RDX

et al. 2013

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EPSRC's High End Computing Programme. We acknowledge the support of the Diamond Light Source, STFC, and the ISIS Neutron and Muon Facility. Supporting information:The remaining DSC thermograms for β-RDX (Figures S1−S4); a comparison between the calculated lattice parameters and unit cell volumes for α-and γ-RDX, compared to previous DFT-D studies as well as relevant experimental data ( Figures S5 and S6); comparison of predicted INS spectra for α-RDX to those for γ-and ε-RDX at similar pressures ( Figures S7 and S8); a comparison of the DFT-D predicted crystallographic parameters with corresponding experimental data for α-, γ-, and ε-RDX (Tables S1, S3, and S4, respectively); full lists of calculated phonon modes as a function of pressure for α-, γ-, and ε-RDX compared to experimental Raman data, including pressure-induced shift values (Tables S2, S5, and S6). This material is available free of charge via the Internet at http://pubs.acs.org Graphical abstract: Abstract:We have performed simulations utilizing the dispersion-corrected density functional theory method (DFT-D) as parametrized by Grimme on selected polymorphs of RDX (cyclotrimethylenetrinitramine). Additionally, we present the first experimental determination of the enthalpy of fusion (ΔH fus ) of the highly metastable β-form of RDX. The characteristics of fusion for β-RDX were determined to be 186.7 ± 0.8 °C, 188.5 ± 0.4 °C, and 12.63 ± 0.28 kJ mol -1 for the onset temperature, peak temperature (or melting point), and ΔH fus , respectively. The difference in experimental ΔH fus for the α-and β-forms of RDX is 20.46 ± 0.92 kJ mol -1 . Ambient-pressure lattice energies (E L ) of the α-and β-forms of RDX have been calculated and are in excellent agreement with experiment. In addition the computationally predicted difference in E L (20.35 kJ mol -1 ) between the α-and β-forms is in excellent agreement with the experimental difference in ΔH fus . The response of the lattice parameters and unit-cell volumes to pressure for the α-and γ-forms have been investigated, in addition to the first high-pressure computational study of the ε-form of RDX-these results are in very good agreement with experimental data. Phonon calculations provide good agreement for vibrational frequencies obtained from Raman spectroscopy, and a predicted inelastic neutron scattering (INS) spectrum of α-RDX shows excellent agreement with experimental INS data determined in this study. The transition energies and intensities are reproduced, confirming that both the eigenvalues and the eigenvectors of the vibrations are correctly described by the DFT-D method. The results of the high-pressure phonon calculations have been used to show that the heat capacities of the α-, γ-, and ε-forms of RDX are only weakly affected by pressure. 4

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“…All experiments were carried out at pressures ranging from 0 to ~7 GPa, and at temperatures ranging from ~295 K to 550 K. Identification of characteristic features in Raman spectra permitted determination of the boundaries between three phases. In Figure 3, we show new phase diagram of RDX [2], along with the previously published [7,8]. The Figure 3a is from this work and the lines represent the best fit to the experimental data; while the Figure 3b is from previous studies.…”

Section: New Phase Diagram and Decomposition Of ε-Rdxmentioning

confidence: 81%

“…Here, we present recent progress in understanding the response of energetic crystal of cyclotrimethylene trinitramine (RDX) to high pressures and high temperatures [1][2][3]. RDX is an important EM used extensively in explosives and monopropellants formulations.…”

Section: Introductionmentioning

confidence: 99%

“…Given that the behaviour of RDX at high pressures and temperatures is of primary interest for understanding the shock initiation, the proper characterization of the HP-HT phase is essential. Therefore, in this work we present recent studies on RDX at high pressures and temperature to address the previous inconsistencies and to complement understanding of processes under shock compression [1,2,[9][10][11][12]. In particular, we focus on: (i) determining details of the vibrational structure of the HP-HT phase, (ii) assessing the claimed association of this phase with -RDX, (iii) providing the refined P-T diagram of RDX, (iv) examining the stability and decomposition of the HP-HT phase, and (v) relating the static compression results to those under shock compression.…”

Section: Introductionmentioning

confidence: 99%

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Energetic materials under high pressures and temperatures: stability, polymorphism and decomposition of RDX

Dreger

2012

J. Phys.: Conf. Ser.

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Phase Diagram of Hexahydro-1,3,5-trinitro-1,3,5-triazine Crystals at High Pressures and Temperatures

Cited by 91 publications

References 21 publications

Compressive Shear Reactive Molecular Dynamics Studies Indicating That Cocrystals of TNT/CL-20 Decrease Sensitivity

Compressive Shear Reactive Molecular Dynamics Studies Indicating That Cocrystals of TNT/CL-20 Decrease Sensitivity

Experimental and DFT-D Studies of the Molecular Organic Energetic Material RDX

Energetic materials under high pressures and temperatures: stability, polymorphism and decomposition of RDX

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