# Pressure‐Driven Reactivity in Dense Methane‐Nitrogen Mixtures

## TL;DR

This study shows how methane and nitrogen can form complex compounds under high pressure and temperature, revealing new chemical reactions in planetary conditions.

## Contribution

The paper demonstrates pressure-driven reactivity in CH4-N2 mixtures, forming new compounds and breaking stable molecular bonds under extreme conditions.

## Key findings

- At pressures above 7 GPa, (CH4)5N2 and (CH4)7(N2)8 compounds form via van der Waals interactions.
- Above 140 GPa, N2 triple bonds break, leading to C−N−H networks and methane dissociation.
- High temperatures reduce required pressure for reactivity, forming NH3 and hydrocarbons at 14 GPa and 670 K.

## Abstract

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.

CH4 and N2 are abundant molecules in our solar system and are the primary constituents of Titan's atmosphere. Under extreme pressures and temperatures within a diamond anvil cell, CH4 and N2 are demonstrated to react to form a range of compounds, dependent on the conditions and initial concentrations. This provides valuable insight into the complexity of the C−N−H ternary system under planetary conditions.