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Highly Shocked Polymer Bonded Explosives at a Nonplanar Interface: Hot-Spot Formation Leading to Detonation

An, Qi and Goddard, William A., III and Zybin, Sergey V. and Jaramillo-Botero, Andres and Zhou, Tingting (2013) Highly Shocked Polymer Bonded Explosives at a Nonplanar Interface: Hot-Spot Formation Leading to Detonation. Journal of Physical Chemistry C, 117 (50). pp. 26551-26561. ISSN 1932-7447. doi:10.1021/jp404753v.

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We report reactive molecular dynamics simulations using the ReaxFF reactive force field to examine shock-induced hot-spot formation followed by detonation initiation in realistic (2.7 million atoms) models of polymer bonded explosives (PBX) with nonplanar interfaces. We considered here two energetic materials (EMs) pentaerythritol tetranitrate (PETN), a common EM for PBX, and silicon pentaerythritol tetranitrate (Si-PETN), which is so extremely sensitive that it has not been possible to characterize its shock properties experimentally. In each case the EM was embedded in a hydroxyl-terminated polybutadiene (HTPB) based polymer binder matrix to form a model of PBX that has a periodic sawtooth nonplanar interface. For the cases in which the shock wave propagates from the EM to polymer (EM→poly), we observed that a hot spot arises from shear localization at the convex polymer asperity. For the case in which the shock direction is inverted (shock wave propagates from the polymer to the EM, EM←poly), we find that a hot spot is initiated at the concave polymer asperity and a second more significant hot spot forms at the convex polymer asperity. This second hot spot is enhanced due to converging shock wave interactions with the nonplanar interface. Under the same shock conditions, the first step in the Si-PETN decomposition is the Si–C–O–X rearrangement to Si–O–C–X through a five centered transition state on the Si that releases 45 kcal/mol of energy that leads to a continuous increase of temperature and pressure in the hot-spot region, until detonation. By contrast, the first step for PETN is NO2 release, which is endothermic by 39 kcal/mol, with the consequence that the hot spot is attenuated by the polymer binder, reaching a steady temperature state involving NO_2 dissociation and HONO formation.

Item Type:Article
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URLURL TypeDescription
An, Qi0000-0003-4838-6232
Goddard, William A., III0000-0003-0097-5716
Jaramillo-Botero, Andres0000-0003-2844-0756
Zhou, Tingting0000-0003-3934-5770
Additional Information:© 2013 American Chemical Society. Received: May 14, 2013; revised: December 2, 2013; published: December 2, 2013. All computations were carried out on the Army HPC systems. We thank Betsy Rice and Larry Davis for assistance. Personnel were supported by ARO (Grants W911NF-05-1-0345 and W911NF-08-1-0124) and by ONR (Grant N00014-09-1-0634). In addition A.J.-B. and W.A.G. received support from the PSAAP project at Caltech (Grant DE-FC52-08NA28613). We thank Mr. Wei-Guang Liu at Caltech for the useful discussions.
Funding AgencyGrant Number
Army Research Office (ARO)W911NF-05-1-0345
Army Research Office (ARO)W911NF-08-1-0124
Office of Naval Research (ONR)N00014-09-1-0634
Department of Energy (DOE) National Nuclear Security AdministrationDE-FC52-08NA28613
Issue or Number:50
Record Number:CaltechAUTHORS:20140127-095341021
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Official Citation:Highly Shocked Polymer Bonded Explosives at a Nonplanar Interface: Hot-Spot Formation Leading to Detonation Qi An, William A. Goddard III, Sergey V. Zybin, Andres Jaramillo-Botero, and Tingting Zhou The Journal of Physical Chemistry C 2013 117 (50), 26551-26561
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43520
Deposited On:27 Jan 2014 21:38
Last Modified:10 Nov 2021 16:39

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