Pressure-induced polymerization and recovery in metastable molecular CHON mixtures

A key issue in high-pressure physics is recovering compressed samples to ambient conditions without losing energy density or other desirable properties, which has rarely been achieved. We investigate a route to pressure-induced polymerization and recovery to ambient conditions using metastable mixtures instead of stable molecular compounds as the starting point. Mixtures of carbon monoxide with various nitrogen oxides are analyzed using density functional theory-based simulations. Additionally, we explore the effect of lowering bonding pressures by adding molecular hydrogen and using path integral molecular dynamics simulations. This provides a comprehensive picture of pressure-induced polymerization in CHON compounds. We will discuss the mechanical causes of hysteresis in these polymers, focusing on local strain energy and its impact on recovery. This approach helps explain why crystalline polymers often break down when released to ambient conditions, while amorphous polymers may survive the decompression process.