High Power Explosive with Good Sensitivity: A 2:1 Cocrystal of CL-20:HMX

A novel energetic cocrystal predicted to exhibit greater
power
and similar sensitivity to that of the current military standard explosive
1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) is presented.
The cocrystal consists of a 2:1 molar ratio of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane
(CL-20), a powerful explosive too sensitive for military use, and
HMX. A predicted detonation velocity 100 m/s higher than that of β-HMX,
the most powerful pure form of HMX, was calculated for the cocrystal
using Cheetah 6.0. In small-scale impact drop tests the cocrystal
exhibits sensitivity indistinguishable from that of β-HMX. This
surprisingly low sensitivity is hypothesized to be due to an increased
degree of hydrogen bonding observed in the cocrystal structure relative
to the crystals of pure HMX and CL-20. Such bonding is prevalent in
this and other energetic cocrystals and may be an important consideration
in the design of future materials. By being more powerful and safe
to handle, the cocrystal presented is an attractive candidate to supplant
the current military state-of-the-art explosive, HMX.