Thermophysical properties of energetic ionic liquids/nitric acid mixtures: Insights from molecular dynamics simulations

Hooper, Justin B.; Smith, Grant D.; Bedrov, Dmitry

doi:10.1063/1.4819903

Cited by 9 publications

(11 citation statements)

References 29 publications

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“…To a first approximation in these drop tests, the observed ignition delay, τ, may be described by τ = 1/ k experimental = 1/ k mixing + 1/ k reaction where the k ’s are the first-order rate coefficients, and an increase in the mixing rate or in the reaction rate will reduce the observed τ. Moreover, previous nonreactive MD simulations of BMIM + DCA – + HNO 3 indicated that mixing of the two liquids is rapid and can increase the temperature of the mixture due to enthalpy release on mixing . The present Figure observations of Na + addition are consistent with this notion and Vogelhuber’s DFT calculations.…”

Section: Results and Discussionsupporting

confidence: 91%

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Ignition Delay Reduction with Sodium Addition to Imidazolium-Based Dicyanamide Ionic Liquid

2018

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A range of ionic liquids (ILs) have been synthesized and modeled to better understand the role of the cation in the ignition of hypergolic ionic liquids. Vogelhuber et al. have shown by density functional theory methods that the addition of sodium cations to an ionic liquid promotes ignition with white fuming nitric acid (WFNA) by lowering energy barriers. To validate this prediction, solid sodium dicyanamide (Na+DCA–) was added at various weight percents to 1-butyl-3-methylimidazolium dicyanamide (BMIM+DCA–). The ignition delay was measured for each mixture with WFNA. Overall, it was found that the Na+DCA– lowered the ignition delay by 11 ms at 7 wt %. The calculations done by Vogelhuber et al. appear to be consistent with this observation. The sodium cation may play a role by orienting the anion with the WFNA resulting in the favorable reaction energetics observed.

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Section: Results and Discussionsupporting

confidence: 91%

“…Moreover, previous nonreactive MD simulations of BMIM + DCA − + HNO 3 indicated that mixing of the two liquids is rapid and can increase the temperature of the mixture due to enthalpy release on mixing. 23 The present Figure 1 observations of Na + addition are consistent with this notion and Vogelhuber's DFT calculations.…”

Section: ■ Results and Discussionsupporting

confidence: 91%

Ignition Delay Reduction with Sodium Addition to Imidazolium-Based Dicyanamide Ionic Liquid

2018

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“…Simulations were conducted at 333 K. MD simulations utilized the atomistic polarizable APPLE&P force field that has been tuned for description of energetic RTILs and their mixtures with nitric acid. 25 Covalent bond lengths were constrained using the velocity-Verlet form of the SHAKE algorithm. 26 The Ewald summation method was used for treatment of long-range electrostatic forces between partial atomic charges and between partial charges and induced dipoles.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Flow-Tube Investigations of Hypergolic Reactions of a Dicyanamide Ionic Liquid Via Tunable Vacuum Ultraviolet Aerosol Mass Spectrometry

et al. 2016

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Hydroxylammonium nitrate (HAN) is a promising candidate to replace highly toxic hydrazine in monopropellant thruster space applications. The reactivity of HAN aerosols on heated copper and iridium targets was investigated using tunable vacuum ultraviolet photoionization time-of-flight aerosol mass spectrometry. The reaction products were identified by their mass-to-charge ratios and their ionization energies. Products include NH 3 , H 2 O, NO, hydroxylamine (HA), HNO 3 , and a small amount of NO 2 at high temperature. No N 2 O was detected under these experimental conditions, despite the fact that N 2 O is one of the expected products according to the generally accepted thermal decomposition mechanism of HAN. Upon introduction of iridium catalyst, a significant enhancement of the NO/HA ratio was observed. This observation indicates that the formation of NO via decomposition of HA is an important pathway in the catalytic decomposition of HAN.

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“…This approach, utilising the APPLE&P transferrable POL force field, has been shown to successfully model both thermodynamic and dynamic properties for a wide variety of systems, including polymers [45], molecular crystals [49], and ionic liquids [41,46,50]. While we refer to the APPLE&P force field as transferrable, it is not generic in nature.…”

Section: Force Field Developmentmentioning

confidence: 98%

Influence of electrostatic interactions on the properties of cyanobiphenyl liquid crystals predicted from atomistic molecular dynamics simulations

2016

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The influence of force field details in all-atom molecular dynamics (MD) simulations on the predicted thermodynamic, structural, and dynamic properties of bulk 4-cyano-4ʹ-pentylbiphenyl (5CB) systems have been investigated in the 292-368 K temperature range. The effect of the molecular dipole moment and the details of dihedral potential for biphenyl unit were investigated using both polarisable (POL) and non-polarisable (NP) versions of the quantum chemistry-based force field. The predicted densities for the nematic and isotropic phases of bulk 5CB were found to be in excellent agreement with available experimental data. The nematic-isotropic transition temperature (T NI ) showed strong sensitivity to the force field details, MD simulations with partial atomic charge distributions and molecular dipole moment corresponding to high-level quantum chemistry calculations predicted an overestimation of the T NI by about 30 K. Rescaling the charges to allow the molecular dipole to be closer to experimentally reported values of 5CB dipole in condensed phases, significantly improved the prediction of T NI as well as other thermodynamic and dynamic properties of 5CB. We also discuss how the structural, thermodynamic, and dynamic properties of bulk 5CB are affected by the flexibility of the central biphenyl dihedral and the inclusion of induced polarisation effects. ARTICLE HISTORY

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Thermophysical properties of energetic ionic liquids/nitric acid mixtures: Insights from molecular dynamics simulations

Cited by 9 publications

References 29 publications

Ignition Delay Reduction with Sodium Addition to Imidazolium-Based Dicyanamide Ionic Liquid

Ignition Delay Reduction with Sodium Addition to Imidazolium-Based Dicyanamide Ionic Liquid

Flow-Tube Investigations of Hypergolic Reactions of a Dicyanamide Ionic Liquid Via Tunable Vacuum Ultraviolet Aerosol Mass Spectrometry

Influence of electrostatic interactions on the properties of cyanobiphenyl liquid crystals predicted from atomistic molecular dynamics simulations

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