Pressure-Driven Reactivity in Dense Methane-Nitrogen Mixtures

Carbon, nitrogen, and hydrogen are among the most abundant elements in the solar system, and our understanding of their interactions is fundamental to prebiotic chemistry. CH₄ and N₂ are the simplest archetypical molecules formed by these elements and are both markedly stable under extremes of pressure. Through a series of diamond anvil cell experiments supported by density functional theory calculations, we observe diverse compound formation and reactivity in the CH₄-N₂ binary system at high pressure. Above 7 GPa two concentration-dependent molecular compounds emerge, (CH₄)₅N₂ and (CH₄)₇(N₂)₈, held together by weak van der Waals interactions. Strikingly, further compression at room temperature irreversibly breaks the N₂ triple bond, inducing the dissociation of CH₄ above 140 GPa, with the near-quenched samples revealing distinct spectroscopic signatures of strong covalently bonded C-N-H networks. High temperatures vastly reduce the required pressure to promote the reactivity between CH₄ and N₂, with NH₃ forming together with longer-chain hydrocarbons at 14 GPa and 670 K, further decomposing into powdered diamond when temperatures exceed 1200 K. These results exemplify how pressure-driven chemistry can cause unexpected complexity in the most simple molecular precursors.