Quantum Mechanics and Molecular Dynamics Calculations provide new evidence for a free‐radical shock initiation model

Walker, F.E.

doi:10.1002/prep.19820070103

Cited by 13 publications

(1 citation statement)

References 17 publications

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“…Walker, Dodson and Graham, , Dremin and Babare, and Coffey and Toton all argue that shock-induced reactions cannot be ordinary thermal reactions and that static thermodynamic equilibria are not established. In a shocked liquid, however, the strain may be uniaxial only during the rise time of the shock front; subsequently the pressure must be hydrostatic…”

Section: Introductionmentioning

confidence: 99%

Reactions of Organic Compounds in Explosive-Driven Shock Waves

Davis

Brower

1996

J. Phys. Chem.

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Shock waves of 1 μs duration and peak temperatures from 900 to 1400 K and pressures from 6 to 16 GPa have been applied to measurement of the rates of a broad spectrum of organic compounds including decomposition of explosives. All reaction rates are consistent with known activation parameters and reaction conditions, and there is no indication of unique chemical processes connected with the subnanosecond rise time of the shock front. Reactions having both positive and negative activation volumes have been studied. Extreme pressure favors ionic reaction mechanisms, whereas extreme temperature favors homolytic mechanisms. Either influence may dominate; thus, cyclohexyl nitrate in benzene gives cyclohexylbenzene by a reaction of Friedel−Crafts type, whereas neopentyl nitrate undergoes homolysis, β-scission, and recombination to give 2-nitro-2-methylpropane. When methanol is used as a solvent, it ionizes extensively and promotes a variety of reactions which ordinarily require acid or base catalysis such as ester interchange and addition of methanol to olefinic bonds.

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Section: Introductionmentioning

confidence: 99%

Reactions of Organic Compounds in Explosive-Driven Shock Waves

Davis

Brower

1996

J. Phys. Chem.

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A New Kinetics and the Simplicity of Detonation

Walker¹

1994

Propellants Explo Pyrotec

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A review is presented of three experiments, as well as a number of molecular dynamics and quantum mechanics calculations. which cast in serious doubt the validity of some concepts and theories of detonation. This doubt led to numerous studies in search of more satisfying concepts, and the results of several of those studies are given. Particularly, a new concept of the kinetics of shock‐induced chemical reaction is presented. This process, designated as physical kinetics, is described as a nonequilibrium, nonthermal process in which chemical reaction rates are determined and regulated by the averaged vibrational velocities of the bonded atoms in condensed systems under the influence of high velocity shock waves. These velocities control the advance of the kinetic energy which leads to the very high impact velocities of the molecules and atoms which cause massive bond fracture in the molecules in extremely short times. It is shown that a detonation model based on the new kinetics model, with the major reactions occurring in times of the order of tenths of picoseconds and in distances on the order of tens of angströms ‐ in the shock or detonation front ‐ can provide a precise and satisfying mathematical and physical description of detonation phenomena.

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Chemical model for intrinsic detonation velocities

Brenner

White

Elert

et al. 2009

Int. J. Quantum Chem.

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Straightforward considerations suggest that chemical reactions including fragmentation processes at or near the front of a chemically sustained shock wave can be important in regulating the shock velocity. This picture is supported by results of recent computer simulations of a model A-B energetic material.The hydrodynamic theory of detonation has enjoyed constant development and apparent success over the past 40 years (for a recent review, see [ 1 ] ). On the other hand, theories which couple the atomic-scale chemical reactions to the shock wave have only recently begun to appear [ 2-10]. For example, after a short initial period, detonations always attain constant velocities that depend only on the properties of the detonating material, and not on the conditions used to initiate the detonation or on the amount of reacted material. It has been argued that this behavior can be explained on the basis of microscopic chemical kinetics [ 11,121, but how such effects couple to the shock propagation has not been clearly established.Detonations travel through solids with supersonic velocities in the range of 3-7 km/s, or 30-70 A/ps. A simple microscopic analysis of this velocity range reveals that the detonation front traverses a typical molecular length in roughly a vibrational period. This rapid chemical kinetics coupled with the violent nature of the process make direct experimental studies of the atomic-scale dynamics of detonations in solids difficult. This time and spatial regime, however, is ideal for study using molecular dynamics computer simulation. To the extent that systems consisting of up to a few thousand atoms mimic the properties of real detonations, molecular dynamics should be capable of providing considerable insight into the atomic-scale chemical dynamics associated with detonating solids.The energy that maintains the shock wave in a detonation comes from solidstate chemical reactions. So far, most previous simulations of detonating solids [ 6-81 have relied on so called "predissociative" pair potentials to model the shockinduced release of chemical energy on an atomic scale. While these types of interactions allow energy release in a straightforward manner, their use also implies that energy is liberated as chemical bonds are broken.

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Quantum Mechanics and Molecular Dynamics Calculations provide new evidence for a free‐radical shock initiation model

Cited by 13 publications

References 17 publications

Reactions of Organic Compounds in Explosive-Driven Shock Waves

Reactions of Organic Compounds in Explosive-Driven Shock Waves

A New Kinetics and the Simplicity of Detonation

Chemical model for intrinsic detonation velocities

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