Thermal decomposition of RDX from reactive molecular dynamics

Abstract

We use the recently developed reactive force field ReaxFF with molecular dynamics to study thermal induced chemistry in RDX ͓cyclic-͓CH 2 N͑NO 2 )] 3 ] at various temperatures and densities. We find that the time evolution of the potential energy can be described reasonably well with a single exponential function from which we obtain an overall characteristic time of decomposition that increases with decreasing density and shows an Arrhenius temperature dependence. These characteristic timescales are in reasonable quantitative agreement with experimental measurements in a similar energetic material, HMX ͓cyclic-͓CH 2 N͑NO 2 )] 4 ]. Our simulations show that the equilibrium population of CO and CO 2 ͑as well as their time evolution͒ depend strongly of density: at low density almost all carbon atoms form CO molecules; as the density increases larger aggregates of carbon appear leading to a C deficient gas phase and the appearance of CO 2 molecules. The equilibrium populations of N 2 and H 2 O are more insensitive with respect to density and form in the early stages of the decomposition process with similar timescales.

Chemomechanics control of tearing paths in graphene

“…However, close-range non-bonded interactions are excluded by using a shielding term. As tested on a number of hydrocarbon-oxygen systems, the ReaxFF has been adequately shown to give energies, reaction pathways, transition states, and reactivity trends that are in great agreement with quantum mechanical calculations and experiments 18,19 , while capable of treating thousands of atoms. The ReaxFF force field has been widely used to study the graphene oxide 20 , graphene peeling from a substrate 21 , and graphene ripping 22 .…”

The ReaxFF reactive force-field: development, applications and future directions

“…32,33 Typically these sets began as non-transferable ReaxFF descriptions constituting independent development branches, but many have later been merged, through extensive refitting, with the combustion (C/B/N/H/O) 34 or aqueous branches (Ni/C/H/O). [35][36][37] It is worth mentioning that the popular ReaxFF high-energy material description 4,5,[38][39][40][41][42][43][44] is older than the combustion branch, but was recently merged-without an obvious loss in accuracy-with this branch. 39,45 Notable developments on the aqueous branch include water-liquid and proton/anion transfer extensions to a range of transition metals and metal oxides (Fe/Ni/Cu/Zn/Al/Ti/ Ca/Si), 7,15,19,35,46-52 along with C/H/O/N/S/P developments aimed at biomolecules and their interactions with inorganic interfaces.…”

“…The current functional form of the ReaxFF potential, best described in the Chenoweth et al 2 4,5 to study RDX initiation.…”

ReaxFF reactive molecular dynamics on silicon pentaerythritol tetranitrate crystal validates the mechanism for the colossal sensitivity

“…This is because similar ReaxFF reactive force fields for other materials have been validated to predict accurately both the reactivity of bonds and mechanical properties of condensed phases. 16,[22][23][24][25][26][27][28][29][30][31] The studies of anisotropic sensitivity of PETN and HMX, 16,24 thermal decomposition of HMX (cyclotetramethylene tetranitramine), TATB (triamino-trinitrobenzene), and RDX, [25][26][27] shock dynamics of RDX and PBX (plastic bonded explosives), [28][29][30][31] and so forth using ReaxFF-RMD lead to the results in accordance with available experimental data, making it practical to describe chemical reactions occurring under various conditions during the large scale dynamical processes involving millions of atoms with currently available computational facilities.…”