Deciphering decomposition pathways of high explosives with cryogenic X-ray Raman spectroscopy

Area of Science:

• Materials Science
• Physical Chemistry
• Spectroscopy

Background:

• High-energy explosives require detailed understanding of decomposition mechanisms.
• Hexanitrohexaazaisowurtzitane (CL-20) is a powerful explosive with a complex cage structure.
• Investigating early-stage decomposition is crucial for safety and performance.

Purpose of the Study:

• To elucidate the initial decomposition pathways of CL-20 under controlled conditions.
• To characterize the molecular intermediates formed during early-stage decomposition.
• To establish a benchmark for understanding high-explosive material stability.

Main Methods:

• Cryogenic X-ray Raman spectroscopy was used to probe molecular changes.
• Ionizing radiation was employed to induce controlled decomposition.
• Systematic variation of radiation dose allowed for observation of spectral evolution.
• First-principles calculations were performed to identify decomposition intermediates and pathways.

Main Results:

• Spectral features at carbon, nitrogen, and oxygen K edges were analyzed.
• C-C and C-N bond cleavage were identified as key early decomposition events.
• Evidence supports N-NO2 homolytic cleavage as the primary initial decomposition pathway.
• The internal cage structure of CL-20 was observed to open during decomposition.

Conclusions:

• The study provides a comprehensive characterization of CL-20 decomposition chemistry.
• N-NO2 homolytic cleavage is identified as the dominant initial reaction.
• Findings offer critical insights into the stability and reactivity of high explosives.
• Combines experimental spectroscopy with theoretical calculations for robust analysis.