MgH₂ as a self-activating fuel: atomic insights into coupled dehydrogenation-oxidation mechanisms

Magnesium hydride (MgH₂) is a promising energetic additive for solid propellants, yet the atomic-scale coupling between its rapid dehydrogenation and subsequent oxidation remains poorly understood. In this study, we developed a high-fidelity neural network potential (NNP) with ab initio accuracy to reveal the distinct combustion mechanisms of MgH₂ versus pure Mg in oxygen environments. Molecular dynamics simulations uncover a unique “Coupled Dehydrogenation-Oxidation” (CDO) mechanism governing MgH₂ combustion. Unlike the diffusion-limited shrinking-core oxidation of Mg, MgH₂ acts as a “self-activating” fuel. We identify a critical “dehydrogenation-induced shattering” process, where the internal pressure from H₂ release mechanically ruptures the MgO passivation shell, creating interconnected channels. This structural damage induces a dominant “channeling effect”, significantly enhancing the inward diffusion of O₂ and enabling volumetric oxidation. Furthermore, the interfacial formation of H₂O generates lattice defects that facilitate oxygen transport, creating a reaction-transport feedback loop that accelerates global kinetics. These findings provide a rigorous theoretical basis for the superior ignition sensitivity of MgH₂ and offer atomistic guidance for designing high-performance energetic formulations.