Direct Reaction between Copper and Nitrogen at High Pressures and Temperatures

Area of Science:

• Materials Science
• Solid State Chemistry
• High-Pressure Physics

Background:

• Transition-metal nitrides are crucial in various technological applications.
• High-pressure and high-temperature synthesis methods are revealing new nitrogen-bearing compounds.
• The chemistry of copper-nitrogen compounds under extreme conditions is not well-established.

Purpose of the Study:

• To synthesize and characterize a novel copper-nitrogen compound.
• To investigate the stability and electronic structure of the synthesized compound.
• To understand the bonding and mechanical properties of copper diazenide.

Main Methods:

• High-pressure and high-temperature synthesis experiments (above 50 GPa, 1500 K).
• Synchrotron X-ray diffraction for structural analysis.
• First-principles calculations for electronic structure and stability.

Main Results:

• Copper diazenide (CuN₂) was successfully synthesized.
• The compound is stable down to 25 GPa.
• CuN₂ is metallic with partially filled N₂ antibonding orbitals, indicating ambiguous Cu oxidation states.
• Observed weak Cu-N bonds and the lowest bulk modulus for any transition-metal nitride.

Conclusions:

• A new transition-metal nitride, copper diazenide (CuN₂), has been discovered.
• CuN₂ exhibits unique electronic properties and mechanical instability.
• The findings expand the known chemistry of transition-metal nitrides under extreme conditions.