Generalized stacking fault energy surfaces in the molecular crystal RDX

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 0K GSF energy surfaces and structures for a set of planes in the-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.