Peierls Stress of Dislocations in Molecular Crystal Cyclotrimethylene Trinitramine
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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Dislocation mediated plasticity in the phase of the energetic molecular crystal cyclotrimethylene trinitramine RDX was investigated using a combination of atomistic simulations and the Peierls Nabarro PN model. A detailed investigation of core structures and dislocation Peierls stress was conducted using athermal atomistic simulations at atmospheric pressure to determine the active slip systems. Generalized stacking fault energy surfaces calculated using atomistic simulations were used in the PN model to also estimate the critical shear stress for dislocation motion. The primary slip plane is found to be 010 in agreement with experimental observations, with the 010 100 slip systems having the lowest Peierls stress. In addition, atomistic simulations predict the 02101 2, 021100, 011100, 001100, and 001010 slip systems to have Peierls stress values small enough to allow plastic activity. However, there are less than five independent slip systems in this material in all situations. The ranking of slip systems based on the Peierls stress values is provided, and implications are discussed in relation to experimental data from nanoindentation and shock-induced plastic deformation.
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