Dissipative particle dynamics with reactions: Application to RDX decomposition

Lı́sal, Martin; Larentzos, James P.; Sellers, Michael S.; Schweigert, Igor V.; Brennan, John G.

doi:10.1063/1.5117904

Cited by 25 publications

(31 citation statements)

References 81 publications

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“…The physics of hot spot formation strongly depends on microstructure and elastic/inelastic material response, while hot spot evolution and growth into a self-sustained burn depends on a complex interplay between thermal conduction and reaction kinetics. Grain scale simulations with coarse grained particles [5][6][7][8][9] or continuum-based multiphysics models [10][11][12][13][14] are a primary tool for explicitly resolving the formation and growth of large hot spots thought to govern initiation response. Accuracy of grain scale model predictions depends on accurate determinations of a wide range of thermodynamic, mechanical, thermal, and chemical material properties that serve as direct inputs or calibrants.…”

Section: Introductionmentioning

confidence: 99%

Predicted Melt Curve and Liquid Shear Viscosity of RDX up to 30 GPa

Kroonblawd

Springer

2021

Preprint

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Recent grain scale simulations of HMX and TATB have shown that predictions for hot spot formation in high explosives are particularly sensitive to accurate determinations of the pressure-dependent melt curve and the shear viscosity of the liquid phase. These physics terms are poorly constrained beyond ambient pressure for the explosive RDX. We adopt an all-atom modeling approach using molecular dynamics (MD) simulations to predict the melt curve of RDX near to detonation conditions (30 GPa) and determine the shear viscosity of the liquid as a function of temperature and pressure above the melt curve. Phase-coexistence simulations were used to determine the melt curve, which is predicted to vary by almost 1100 K as the pressure increases from 0 GPa to 30 GPa. Equilibrium MD simulations and the Green-Kubo formalism were used to obtain the pressure-temperature dependent shear viscosity. The shear viscosity of RDX is predicted to be of similar magnitude to the viscosity of TATB at low GPa-range pressures, and to be roughly an order of magnitude lower than the viscosity of HMX. The temperature dependence of the shear viscosity is Arrhenius at a given pressure, and the exponential pre-factor and activation term exhibit a strong, yet complicated, pressure dependence. An empirical pressure-temperature dependent function for RDX shear viscosity is developed that simultaneously captures a wide range of MD predictions while taking an analytic form that extrapolates smoothly beyond the fitted regime. The relative strength of the pressure and temperature dependencies of these two physics terms is found to be of similar magnitude for RDX, HMX, and TATB, which motivates incorporating these results in future RDX grain scale modeling.

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Section: Introductionmentioning

confidence: 99%

Predicted Melt Curve and Liquid Shear Viscosity of RDX up to 30 GPa

Kroonblawd

Springer

2021

Preprint

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“…It should be noted that the DPD version employed here cannot model the reaction of dissociation of the sulfonic acid group: this would require a reactive DPD model (see, e.g. , refs – ). To be more precise, a water molecule should be allowed to dissociate to form a sulfonic acid group located in the film and a hydroxyl released to the surrounding water.…”

Section: Resultsmentioning

confidence: 99%

Interactions of Crosslinked Polyacrylic Acid Polyelectrolyte Gels with Nonionic and Ionic Surfactants

et al. 2021

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The morphology and stability of surfactant-loaded polyelectrolyte gels are of great interest for a variety of personal care, cosmetic, and pharmaceutical products. However, the mechanisms of surfactant interactions with gel-forming polymers are poorly understood and experimentally challenging. The aim of this work is to explore in silico the specifics of surfactant absorption within polyelectrolyte gels drawing on the examples of typical non-ionic octaethylene glycol monooctyl ether (C 8 E 8 ) and anionic sodium dodecyl sulfate (SDS) surfactants and polyacrylic acid modified with hydrophobic sidechains mimicking the practically important Carbopol polymer. Using the systematically parameterized coarsegrained dissipative particle dynamics models, we generate and characterize the equilibrium conformations and swelling of the polymer films in aqueous solutions with the surfactant concentrations varied up to the critical micelle concentration (cmc). We discover the striking difference in interactions of Carbopol-like polymers with nonionic and ionic surfactants under mildly acidic conditions. The sorption of C 8 E 8 within the polymer film is found substantial. As the surfactant concentration increases, the polymer film swells and, close to cmc, becomes unstable due to the formation and growth of water pockets filled with surfactant micelles. Sorption of SDS at the same bulk concentrations is found much lower, with only about 1% of surfactant mass fraction achieved at cmc. As the SDS concentration increases further, a lamellae structure is formed within the film, which remains stable. Reduced swelling and higher stability indicate better prospects of using SDS-type surfactants with Carbopol-based gels in formulations for detergents and personal care products.

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“…As RDX decomposes into the product gas species shown in Reaction R 1 -R 4 , the interaction model accounts for these changes in composition. A full description of the energy conserving DPD-RX method, model, and parameters is given elsewhere [14,29,84].…”

Section: Models and Methodsmentioning

confidence: 99%

Forging of Hierarchical Multiscale Capabilities for Simulation of Energetic Materials

Barnes

Leiter

Larentzos

et al. 2019

Propellants Explo Pyrotec

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We present new capabilities for investigation of microstructure in energetic material response for both explicit large‐scale and multiscale simulations. We demonstrate the computational capabilities by studying the effect of porosity on the reactive shock response of a coarse‐grain (CG) model of the energetic material cyclotrimethylene trinitramine (RDX), the non‐reactive equation of state for a porous representative volume element (RVE) of CG RDX, and utilization of available supercomputing resources for speculative sampling to accelerate hierarchical multiscale simulations. Small amounts of porosity (up to 4 %) are shown to have significant effect on the initiation of reactive CG RDX using large‐scale reactive dissipative particle dynamics simulations. Non‐reactive RVEs are shown to undergo a porosity‐dependent pore collapse at hydrostatic conditions, and an existing automation framework is shown to be easily modified for the incorporation of microstructure while retaining reliable convergence properties. A novel predictive sampling method based on use of kernel density estimators is shown to effectively accelerate time‐to‐solution in a multiscale simulation, scaling with free CPU cores, while making no assumptions about the underlying physics for the data being analyzed. These multidisciplinary studies of distinct yet connected problems combine to provide methodological insights for high‐fidelity modeling of reactive systems with microstructure.

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Dissipative particle dynamics with reactions: Application to RDX decomposition

Cited by 25 publications

References 81 publications

Predicted Melt Curve and Liquid Shear Viscosity of RDX up to 30 GPa

Predicted Melt Curve and Liquid Shear Viscosity of RDX up to 30 GPa

Interactions of Crosslinked Polyacrylic Acid Polyelectrolyte Gels with Nonionic and Ionic Surfactants

Forging of Hierarchical Multiscale Capabilities for Simulation of Energetic Materials

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