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Updated: May 23, 2026
08:14
Ammonia Synthesis at Low Pressure
Published on: August 23, 2017
Structural phase transitions induced by pressure in ammonium borohydride
Roxana Flacau1, Yansun Yao, Dennis D Klug
1Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario, Canada K1A 0R6. chris.ratcliffe@nrc-cnrc.gc.ca.
Physical Chemistry Chemical Physics : PCCP
|April 12, 2012
Summary
High-pressure studies reveal two phase transitions in ammonium borohydride (NH4BH4) at 1.5 and 3.4 GPa. These transitions alter the material
Area of Science:
- Materials Science
- Solid-State Chemistry
- High-Pressure Physics
Background:
- Ammonium borohydride (NH4BH4) is a hydrogen-rich material with potential applications in hydrogen storage.
- Understanding its structural behavior under pressure is crucial for exploring its properties.
Purpose of the Study:
- To investigate the phase transitions and structural evolution of NH4BH4 under high pressure.
- To elucidate the crystal structures of the different phases of NH4BH4.
Main Methods:
- Synchrotron radiation powder X-ray diffraction (XRD).
- Raman spectroscopy.
- Car-Parrinello molecular dynamics (MD) calculations.
- Ab initio computational techniques.
- Rietveld refinement.
Main Results:
- Two distinct phase transitions were observed at 1.5 GPa and 3.4 GPa.
- The ambient cubic phase transforms into a disordered intermediate phase, followed by an orthorhombic CsCl-type structure at higher pressures.
- The crystal structure of the high-pressure orthorhombic phase was determined.
Conclusions:
- Ammonium borohydride undergoes significant structural rearrangements under pressure.
- The determined structures provide insights into the behavior of hydrogen-rich materials under extreme conditions.
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