(528d) Coarse-Grain Modeling of Energetic Materials

A recently developed multi-scale coarse-graining (MS-CG) method [1-3] for systematic development of particle-based coarse-grain (CG) models is applied to two conventional energetic materials, nitromethane and cyclotrimethylenetrinitramine (RDX). The MS-CG method represents an efficient force-matching based strategy for constructing coarse-grain potentials as a pairwise approximation of the atomistic all-particle free energy. For nitromethane one-bead and two-bead CG models fitted to liquid phase simulations, and for RDX one-bead and four-bead CG models fitted to crystal and molten phase simulations, are presented. To improve thermodynamic state-point transferability, a dependence on a particle density is introduced to the CG models. Performance of resulting density dependent CG models in simulations of crystal and liquid phases of nitromethane and RDX is evaluated against underlying atomistic simulations and experiment. The CG models perform reasonably well in a reproduction of various properties, including crystal and liquid structure, thermal expansion properties, and bulk moduli. The CG models appear to be well transferable across a broad range of temperatures and pressures and can be applied to simulate inert shocked states of nitromethane and RDX.

This effort is supported by the recently established Institute for Multi-Scale Reactive Modeling of Insensitive Munitions (MSRM), which is a multi-team effort led by the U.S. Army Research Laboratory and the U.S. Army Armament Research, Development and Engineering Center, involving various other national laboratories and academic groups totaling over 20 scientists.

References:

[1] S. Izvekov and G. A. Voth, J. Chem. Phys. 123, 134105 (2005).

[2] W. G. Noid, J.-W. Chu, G. S. Ayton, V. Krishna, S. Izvekov, G. A. Voth, A. Das and H. C. Andersen, J. Chem. Phys. 128, 244114 (2008).

[3] S. Izvekov, P. W. Chung and B. M. Rice, J. Chem. Phys., (2010) [to be published].