High-Temperature Decomposition of Diisopropyl Methylphosphonate on Alumina: Mechanistic Predictions from Ab Initio Molecular Dynamics

The enhanced degradation of organophosphorous-based chemical warfare agents (CWAs) on metal oxide surfaces holds immense promise for neutralization efforts; however, the underlying mechanisms in this process remain poorly understood. For the first time, we utilize large-scale quantum calculations to probe the high-temperature degradation of diisopropyl methylphosphonate (DIMP), a nerve agent simulant. Our Born–Oppenheimer molecular dynamics (BOMD) calculations show that the γ-Al 2 O 3 surface shows immense promise for quickly adsorbing and destroying CWAs. We find that the alumina surface quickly adsorbs DIMP at all temperatures, and subsequent decomposition of DIMP proceeds via a propene elimination. Our BOMD calculations are complemented with metadynamics simulations to produce free energy paths, which show that the activation barrier decreases with temperature and that DIMP readily decomposes on γ-Al 2 O 3 . Our first-principle BOMD and metadynamics simulations provide crucial diagnostics for sarin decomposition models and mechanistic information for examining CWA decomposition reactions on other candidate metal oxide surfaces.