Generalized stacking fault energy surfaces in the molecular crystal αRDX

Abstract

The generalized stacking fault (GSF) energy surfaces in the organic energetic molecular crystal, hexahydro-1,3,5-trinitro-s-triazine (RDX), were studied through atomistic simulations. Using a fully flexible molecular potential in highly damped molecular dynamics simulations, we determined quenched 0 K GSF energy surfaces and structures for a set of planes in the α-polymorph RDX crystal and subsequently compare predictions of slip or cleavage with available experimental observations. To account for the steric contributions and elastic shearing due to the presence of flexible molecules, a modified calculation procedure for the GSF energy surface is proposed that enables the distinction of elastic shear energy from the energy associated with the interfacial displacement discontinuity at the slip plane. Comparisons of the unstable stacking fault energy with the surface energy are used to differentiate cleavage planes from likely slip planes, and the calculations are found to be largely in agreement with available experimental data.

Keywords:

• RDX
• molecular crystal
• generalized stacking fault energy surface
• slip system

Acknowledgements

Support is gratefully acknowledged from the US Army Research Laboratory SCEP program and the DoD Higher Performance Computing Modernization Office through the Multiscale Reactive Modeling of Insensitive Munitions Software Applications Institute. Computing support was provided by the DoD Supercomputing Resource Center located at the Army Research Laboratory. We are grateful to Brent Kraczek, Jaroslaw Knap and Betsy Rice for helpful discussions and guidance throughout this work.