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Related Experiment Video

Updated: May 30, 2026

Ammonia Synthesis at Low Pressure

Ammonia Synthesis at Low Pressure

Published on: August 23, 2017

The ammonia-hydrogen system under pressure.

Bethany A Chidester¹, Timothy A Strobel

¹Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, D.C. 20015, USA.

The Journal of Physical Chemistry. A

|August 11, 2011

Summary

This summary is machine-generated.

Binary mixtures of hydrogen and ammonia exhibit phase separation at high pressures. This study proposes a P-x phase diagram for the ammonia-hydrogen system, relevant for planetary science and materials development.

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Ammonia Synthesis at Low Pressure

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Area of Science:

High-pressure physics and chemistry
Planetary science
Materials science

Background:

Understanding the behavior of hydrogen and ammonia mixtures is crucial for modeling planetary interiors.
Previous studies have explored limited aspects of the ammonia-hydrogen (NH(3)-H(2)) system.

Purpose of the Study:

To investigate the phase behavior of binary NH(3)-H(2) mixtures under high pressure.
To construct a pressure-composition (P-x) phase diagram for the NH(3)-H(2) system.
To explore implications for planetary ices and hydrogen storage.

Main Methods:

Compression of NH(3)-H(2) mixtures in diamond anvil cells up to 15 GPa.
Characterization using optical microscopy, Raman spectroscopy, and synchrotron X-ray diffraction.

Main Results:

Observed two-phase coexistence of liquid ammonia and fluid hydrogen below 1.2 GPa.
Complete immiscibility occurred after ammonia froze into phase III at 1.2 GPa.
Ammonia phase III to phase IV transition occurred at ~3.8 GPa, and hydrogen solidified at ~5.5 GPa, consistent with pure component transitions.

Conclusions:

A P-x phase diagram for the NH(3)-H(2) system was proposed.
Findings have implications for understanding planetary ice compositions.
The study suggests potential applications in molecular compound formation and hydrogen storage materials.