Unraveling Antagonistic Collision-Controlled Reactivity in Energetic Molecular Perovskites with Deep Potential Molecular Dynamics

Abstract

The precise regulation of chemical decompositions in energetic materials, whether towards rapid ignition or stable endurance, requires atomic-scale principles governing reactivity, which remain elusive yet. Herein, we resolve this challenge through deep potential molecular dynamics (DPMD) simulations, uncovering a universal collision-control principle in energetic molecular perovskites, ${\text{(H}}_2{\text{dabco)B(ClO}}_4{\text{)}}_3$, where ${\text{H}}_2{\text{dabco}}^{2+}$ = 1,4-diazabicyclo[2.2.2]octane-1,4-diium, B = ${\text{Na}}^{+}$, ${\text{K}}^{+}$, ${\text{Rb}}^{+}$, ${\text{NH}}_4^{+}$ for DAP-1, DAP-2, DAP-3 and DAP-4, respectively. Atomic-scale simulation with Arrhenius fitting for over 100-ps trajectories reveals that increasing B-site ionic radius (${\text{Na}}^{+}<{\text{K}}^{+}<{\text{Rb}}^{+}$) simultaneously reduces both activation energy $E_a$, which enhances reactivity, and pre-exponential factor $A$ which suppresses collision probabilities for hydrogen transfer between site $X$ and site $A$, with sharply opposing kinetic consequences. This duality well explains the peak stability and insensitivity in ${\text{K}}^{+}$-based DAP-2, which optimally balance thermal endurance and collision dissipation. For ammonium-based DAP-4, though the radius of ${\text{NH}}_4^{+}$ is close to ${\text{K}}^{+}$, the reactive B-site cation triggers proton transfer that promotes $\text{C-H}$ bond rupture. By linking static cation radii to dynamic $E_a$-ln$(A)$ coupling, we rationalize non-monotonic decomposition temperatures (${\text{K}}^{+}>{\text{NH}}_4^{+}>{\text{Rb}}^{+}>{\text{Na}}^{+}$) macroscopic stability and establishes cornerstones for universal energetic material design.