Molecular Simulations of Shear-Induced Dynamics in Nitromethane

Report No. ARL-TN-0784
Authors: Brad A Steele; James P Larentzos
Date/Pages: September 2016; 24 pages
Abstract: The atomistic dynamics of the shear response of single-crystal and bicrystal nitromethane (NM) are simulated using molecular dynamics simulations. The atomic interactions are described using a recently optimized ReaxFF-lg potential trained specifically for NM. We found that NM transforms to a disordered state upon shear at a pressure of 20 GPa and 298 K. Shear simulations of several different orientations show that the maximum shear stress and shear angle where the transformation to the disordered state occurs are highly dependent on the crystallographic orientation of NM. The dynamics that occur during shear in several different single-crystal orientations are elucidated. Shear simulations in bicrystal NM show more complex behavior, and the disordered state typically originates at the grain boundary and then grows. The shear response is simulated at pressures and temperatures where NM has been experimentally observed to undergo chemical decomposition when shear stress is applied. Although no reactions occur in these simulations, these results shed light on the short time scale reaction pathways that NM can take during shear-induced initiation.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2016