Accelerated Degradation of Hexanitrohexaazaisowurtzitane (CL‐20) by Lithium Hydroxide

ABSTRACT Density functional theory was employed to investigate how lithium hydroxide (LiOH), generated from Li 2 O on humid glass‐ceramic substrates, lowers the barrier for the rate‐determining N─N bond cleavage in the thermal decomposition of ε CL‐20. Calculations of hexanitrohexaazaisowurtzitane (CL‐20) interactions with OH − , intact LiOH, Li + , and in situ‐generated water identified three classes of low‐barrier pathways for OH − /LiOH‐assisted rate acceleration: hydrogen abstraction followed by N─N scission, insertion into nitramine N─N bonds, and nucleophilic cage‐ring opening. Free OH − reacts with CL‐20 through pathways that exhibit activation energies significantly lower than those associated with intact LiOH. In each pathway, the resulting undercoordinated fragments underwent structural reorganization, forming C─N double bonds and attaching nitro/nitrite or hydroxyl substituents, which contributed tens of kilocalories per mole of additional stabilization. In situ‐generated water remained bound to the CL‐20 intermediate and influenced product distributions. The primary role of Li + was to stabilize undercoordinated intermediates and charged leaving groups. While the dominant pathway in the CL‐20 crystal is determined by local geometry and accessibility, the identified molecular pathways reduce the effective N─N cleavage barrier, providing an explanation for the accelerated degradation of CL‐20 observed on glass‐ceramic surfaces.