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.