High-Pressure Synthesized Lithium Pentazolate Compound Metastable under Ambient Conditions

Area of Science:

• High-energy materials science
• Inorganic chemistry
• Materials under extreme conditions

Background:

• Polynitrogen compounds are pursued for high-performance propellants and explosives.
• Achieving both high nitrogen content and ambient stability remains a challenge.
• Previous research has not fully met these critical material metrics.

Purpose of the Study:

• To synthesize and characterize a novel stable high-nitrogen compound.
• To investigate the formation of the pentazolate anion under high pressure.
• To assess the material's properties for potential energetic applications.

Main Methods:

• High-pressure synthesis involving laser heating of lithium in molecular nitrogen (N2) at 45 GPa.
• Recovery of the synthesized material under ambient conditions.
• Characterization using Raman spectroscopy, mass spectrometry, and X-ray diffraction.

Main Results:

• Successful synthesis and recovery of lithium pentazolate (LiN5) under ambient conditions.
• Confirmation of the cyclo-N5- anion using Raman spectroscopy and mass spectrometry.
• Determination of a monoclinic crystal structure, with experimental volume matching theoretical predictions.

Conclusions:

• The synthesis of stable lithium pentazolate (LiN5) represents a significant advancement in polynitrogen chemistry.
• The formation of the cyclo-N5- anion is confirmed, offering a new energetic material.
• This discovery paves the way for developing advanced, stable, high-nitrogen energetic materials.