On the Reactivity of Hydrogen-Helium and Hydrogen-Nitrogen at High Pressures

TL;DR

This study uses Raman spectroscopy to explore the behavior of hydrogen-helium and hydrogen-nitrogen mixtures at high pressures, revealing no chemical association in H-He but N2-H2 compound formation in N2-H2 mixtures above 50 GPa.

Contribution

It provides the first detailed high-pressure analysis showing the absence of H-He chemical association and clarifies N2-H2 interactions, correcting previous claims of H2-He bonding.

Findings

No chemical association of H2 and He up to 250 GPa.

Formation of N2-H2 compounds above 50 GPa.

Misinterpretation of H2-He association due to N2 contamination.

Abstract

Through a series of Raman spectroscopy studies, we investigate the behaviour of hydrogen-helium and hydrogen-nitrogen mixtures at high pressure across wide ranging concentrations. We find that there is no evidence of chemical association, miscibility, nor any demixing of hydrogen and helium in the solid state up to pressures of 250 GPa at 300 K. In contrast, we observe the formation of concentration-dependent N$_2$-H$_2$ van der Waals solids, which react to form N-H bonded compounds above 50 GPa. Through this combined study, we can demonstrate that the recently claimed chemical association of H$_2$-He can be attributed to significant N$_2$ contamination and subsequent formation of N$_2$-H$_2$ compounds.