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Molecular Dynamics Simulations of Shock-Defect Interactions in Two-Dimensional Nonreactive Crystals

Published online by Cambridge University Press:  15 February 2011

Robert S. Sinkovits
Affiliation:
Naval Research Laboratory, Laboratory for Computational Physics and Fluid Dynamics, Washington, DC 20375-5000
Lee Phillips
Affiliation:
Naval Research Laboratory, Laboratory for Computational Physics and Fluid Dynamics, Washington, DC 20375-5000
Elaine S. Oran
Affiliation:
Naval Research Laboratory, Laboratory for Computational Physics and Fluid Dynamics, Washington, DC 20375-5000
Jay P. Boris
Affiliation:
Naval Research Laboratory, Laboratory for Computational Physics and Fluid Dynamics, Washington, DC 20375-5000
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Abstract

The interactions of shocks with defects in two-dimensional square and hexagonal lattices of particles interacting through Lennard-Jones potentials are studied using molecular dynamics. In perfect lattices at zero temperature, shocks directed along one of the principal axes propagate through the crystal causing no permanent disruption. Vacancies, interstitials, and to a lesser degree, massive defects are all effective at converting directed shock motion into thermalized two-dimensional motion. Measures of lattice disruption quantitatively describe the effects of the different defects. The square lattice is unstable at nonzero temperatures, as shown by its tendency upon impact to reorganize into the lower-energy hexagonal state. This transition also occurs in the disordered region associated with the shock-defect interaction. The hexagonal lattice can be made arbitrarily stable even for shock-vacancy interactions through appropriate choice of potential parameters. In reactive crystals, these defect sites may be responsible for the onset of detonation. All calculations are performed using a program optimized for the massively parallel Connection Machine.

Type
Research Article
Copyright
Copyright © Materials Research Society 1993

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