DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Intergranular Hotspots: A Molecular Dynamics Study on the Influence of Compressive and Shear Work

Journal Article · · Journal of Physical Chemistry. C

Numerous crystal- and microstructural-level mechanisms are at play in the formation of hotspots, which are known to govern high explosives initiation behavior. Most of these mechanisms, including pore collapse, interfacial friction, and shear banding, involve both compressive and shear work done within the material and have thus far remained difficult to separate. Here, we assess hotspots formed at shocked crystal–crystal interfaces using quasi-1D molecular dynamics simulations that isolate effects due to compression and shear. Two high explosive materials are considered (TATB and PETN) that exhibit distinctly different levels of molecular conformational flexibility and crystal packing anisotropy. Temperature and intramolecular strain energy localization in the hotspot are assessed through parametric variation of the crystal orientation and two velocity components that respectively modulate compression and shear work. The resulting hotspots are found to be highly localized to a region within 5–20 nm of the crystal–crystal interface. Compressive work plays a considerably larger role in localizing temperature and intramolecular strain energy for both materials and all crystal orientations considered. Shear induces a moderate increase in energy localization relative to unsheared cases only for relatively weak compressive shock pressures of approximately 10 GPa. These results help isolate and rank the relative importance of hotspot generation mechanisms and are anticipated to guide the treatment of crystal–crystal interfaces in coarse-grained models of polycrystalline high-explosive materials.

Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA); US Department of the Navy, Office of Naval Research (ONR)
Grant/Contract Number:
89233218CNA000001; AC52-07NA27344; B648789; N00014-16-1-2557
OSTI ID:
1994465
Alternate ID(s):
OSTI ID: 1993235
Report Number(s):
LLNL-JRNL-844913; LA-UR-23-21420; 1067933
Journal Information:
Journal of Physical Chemistry. C, Vol. 127, Issue 20; ISSN 1932-7447
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

References (59)

Continuum and molecular dynamics simulations of pore collapse in shocked β -tetramethylene tetranitramine ( β -HMX) single crystals journal January 2021
Atomistic Mechanism for Hot Spot Initiation journal December 2002
Multiscale modeling of shock wave localization in porous energetic material journal January 2018
Shock-induced shear bands in an energetic molecular crystal: Application of shock-front absorbing boundary conditions to molecular dynamics simulations journal July 2008
Shock wave focusing using geometrical shock dynamics journal October 1997
Shock-Induced Inelastic Deformation in Oriented Crystalline Pentaerythritol Tetranitrate journal November 2011
Atomistic Simulation of Orientation Dependence in Shock-Induced Initiation of Pentaerythritol Tetranitrate journal January 2013
Shock Waves in High-Energy Materials: The Initial Chemical Events in Nitramine RDX journal August 2003
Equation of state and reaction rate for condensed-phase explosives journal September 2005
Fourier-like Thermal Relaxation of Nanoscale Explosive Hot Spots journal September 2021
Direct numerical simulation of shear localization and decomposition reactions in shock-loaded HMX crystal journal May 2015
Tandem Molecular Dynamics and Continuum Studies of Shock‐Induced Pore Collapse in TATB journal November 2019
Force-induced activation of covalent bonds in mechanoresponsive polymeric materials journal May 2009
Fast Parallel Algorithms for Short-Range Molecular Dynamics journal March 1995
Polarizable and Nonpolarizable Force Fields for Alkyl Nitrates journal January 2008
Dynamics of void collapse in shocked energetic materials: physics of void–void interactions journal March 2013
Virtual melting as a new mechanism of stress relaxation under high strain rate loading journal July 2012
Shock Wave Initiation of Pentaerythritol Tetranitrate Single Crystals:  Mechanism of Anisotropic Sensitivity journal November 2000
A Hotspot’s Better Half: Non-Equilibrium Intra-Molecular Strain in Shock Physics journal March 2021
Hotspot formation due to shock-induced pore collapse in 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane (HMX): Role of pore shape and shock strength in collapse mechanism and temperature journal May 2020
The focusing of weak shock waves journal February 1976
High Explosive Ignition through Chemically Activated Nanoscale Shear Bands journal May 2020
Inducing and quantifying forbidden reactivity with single-molecule polymer mechanochemistry journal February 2015
Three-dimensional microstructure-explicit and void-explicit mesoscale simulations of detonation of HMX at millimeter sample size scale journal March 2020
A generalized crystal-cutting method for modeling arbitrarily oriented crystals in 3D periodic simulation cells with applications to crystal–crystal interfaces journal October 2016
Modeling The Effects of Shock Pressure and Pore Morphology on Hot Spot Mechanisms in HMX journal June 2018
Role of dynamical compressive and shear loading on hotspot criticality in RDX via reactive molecular dynamics journal August 2020
Exact method for the simulation of Coulombic systems by spherically truncated, pairwise r−1 summation journal May 1999
Interplay of Mechanochemistry and Material Processes in the Graphite to Diamond Phase Transformation preprint January 2023
A unified formulation of the constant temperature molecular dynamics methods journal July 1984
Shock-induced plasticity in tantalum single crystals: Interatomic potentials and large-scale molecular-dynamics simulations journal October 2013
Shear activation of mechanophore-crosslinked polymers journal January 2011
Ultrafast Chemistry under Nonequilibrium Conditions and the Shock to Deflagration Transition at the Nanoscale journal September 2015
Force-dependent chemical kinetics of disulfide bond reduction observed with single-molecule techniques journal April 2006
Chemistry Under Shock Conditions journal July 2021
Comments on P3M, FMM, and the Ewald method for large periodic Coulombic systems journal June 1996
Mechanochemistry of Metal–Organic Frameworks under Pressure and Shock journal September 2020
Irreversible Deformation Mechanisms for 1,3,5-Triamino-2,4,6-Trinitrobenzene Single Crystal through Molecular Dynamics Simulations journal May 2018
Systematic Builder for All‐Atom Simulations of Plastically Bonded Explosives journal June 2022
Theoretical determination of anisotropic thermal conductivity for initially defect-free and defective TATB single crystals journal November 2014
Energy localization efficiency in 1,3,5-trinitro-2,4,6-triaminobenzene pore collapse mechanisms journal January 2023
Molecular mechanics modeling of shear and the crystal orientation dependence of the elastic precursor shock strength in pentaerythritol tetranitrate journal September 1994
Strongly Anisotropic Thermomechanical Response to Shock Wave Loading in Oriented Samples of the Triclinic Molecular Crystal 1,3,5-Triamino-2,4,6-trinitrobenzene journal October 2021
Understanding the shock and detonation response of high explosives at the continuum and meso scales journal March 2018
Molecular Dynamics of Shock Waves in Three-Dimensional Solids: Transition from Nonsteady to Steady Waves in Perfect Crystals and Implications for the Rankine-Hugoniot Conditions journal November 1979
Extemporaneous Mechanochemistry: Shock-Wave-Induced Ultrafast Chemical Reactions Due to Intramolecular Strain Energy journal July 2022
Atomic-level view of inelastic deformation in a shock loaded molecular crystal journal August 2007
Void collapse generated meso-scale energy localization in shocked energetic materials: Non-dimensional parameters, regimes, and criticality of hotspots journal January 2019
Anisotropy in surface-initiated melting of the triclinic molecular crystal 1,3,5-triamino-2,4,6-trinitrobenzene: A molecular dynamics study journal September 2015
The Potential Energy Hotspot: Effects of Impact Velocity, Defect Geometry, and Crystallographic Orientation journal February 2022
A molecular dynamics simulation study of crystalline 1,3,5-triamino-2,4,6-trinitrobenzene as a function of pressure and temperature journal December 2009
Ultrafast Chemical Reactions in Shocked Nitromethane Probed with Dynamic Ellipsometry and Transient Absorption Spectroscopy journal March 2014
Dynamic fracture and hot-spot modeling in energetic composites journal February 2018
Anisotropic strength behavior of single-crystal TATB journal December 2021
LAMMPS - a flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales journal February 2022
Deviatoric stress driven transient melting below the glass transition temperature in shocked polymers journal July 2022
Activating catalysts with mechanical force journal April 2009
On the shock induced failure of brittle solids journal October 1998
Many-Body Mechanochemistry: Intra-molecular Strain in Condensed Matter Chemistry journal February 2022