jp8b06509_si_001.pdf (858.57 kB)
Role of Molecular Disorder on the Reactivity of RDX
journal contribution
posted on 2018-11-01, 00:00 authored by Michael Sakano, Brenden Hamilton, Md Mahbubul Islam, Alejandro StrachanShock initiation
of heterogeneous high-energy materials is often
preceded by the loss of crystalline order around hotspots where mechanical
energy is localized and chemical reactions start. We use molecular
dynamics (MD) simulations with the reactive force field ReaxFF to
determine the impact of molecular disorder on the reactivity of the
high-energy material RDX under fast homogeneous heating and hotspots.
Under fast heating to identical temperatures, amorphous samples exhibit
faster decomposition and reaction than their crystalline counterparts.
Following heating, the crystalline samples undergo fast endothermic
processes associated with the loss of crystalline order that occur
in timescales shorter than chemical decomposition and reduce the actual
temperature of the reaction. Once this process is accounted for and
actual decomposition temperatures are determined, both amorphous and
crystalline samples follow identical kinetics. We also characterize
the critical temperature required for a hotspot 10 nm in diameter
to become critical and turn into a deflagration wave. In both crystalline
and amorphous samples, hotspots with initial temperatures of 1650
K and higher result in self-sustained deflagration waves and those
at 1600 K quench. We observe slightly faster propagation in the amorphous
samples with initial velocities increasing with temperature. The higher
reactivity of amorphous samples is not large enough to explain the
significantly increased reactivity in hotspots formed after shock-induced
pore collapse observed recently in large-scale MD simulations.