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

TLDR

The 2:1 CL‑20:HMX cocrystal combines the high‑energy CL‑20 with HMX, and its extensive hydrogen bonding is characteristic of energetic cocrystals and may guide future material design. The study presents a novel CL‑20:HMX cocrystal predicted to deliver higher power while maintaining sensitivity comparable to military‑grade HMX. The cocrystal’s unexpectedly low sensitivity is attributed to increased hydrogen bonding within its crystal structure relative to pure HMX and CL‑20. Predicted detonation velocity exceeds β‑HMX by 100 m/s, and impact drop tests show sensitivity indistinguishable from β‑HMX, making the cocrystal a powerful yet safe candidate to replace HMX.

Abstract

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.