New C-H-N compounds discovered under planetary-relevant conditions

Extreme conditions create stable compounds, offering planetary insights.

Carbon, nitrogen, and hydrogen are crucial elements in the solar system. They are essential for the origins of life. The simplest molecules from these elements are methane (CH₄) and nitrogen (N₂). These typically do not react under normal conditions, but on Saturn’s moon Titan, interactions suggest otherwise. To understand how these reactions might happen deep within planets, researchers examined these molecules under extreme pressures and temperatures.

During the research, mixtures of methane and nitrogen were squeezed using a tool called a diamond anvil cell, to simulate high pressure environments, with fascinating results.

At pressures above 7 GPa (~70,000 atm) two new compounds (CH₄)₇(N₂)₈ and (CH₄)₅N₂ formed. Remarkably, when pressure exceeded 160 GPa, the methane and nitrogen molecules broke apart, forming a new material with carbon, hydrogen, and nitrogen atoms bonded tightly together. Surprisingly, this new material remained stable even after the pressure was removed.

The research team also discovered that heating methane-nitrogen mixtures to over 1400°C at 40 GPa caused it to break down into powdered diamond and ammonia.

The findings can be found in a paper published in Angewandte Chemie by PhD student Hannah Shuttleworth. The project was led by colleagues from the School’s Institute for Condensed Matter and Complex Systems (ICMCS): Dr Ross Howie, Dr Miriam Peña-Alvarez and Professor Andreas Hermann.

These discoveries provide new insights into chemical processes potentially occurring in planetary interiors, contributing significantly to our understanding of planetary chemistry.

Dr Ross Howie, ERC Research Fellow said:

This research highlights how pressure alone can be used to induce reactions in seemingly stable systems, which is crucial in mimicking the conditions found within the interiors of planets.